Rear ECU Drowned

My 2005 Boxster 987 has been sitting happily in the drive until one night, we had about 3 inches of rain. My wife noticed that the rear centre light was blinking and the left brake light was on. then the spoiler extended by itself. Before I had a change to ask Mr Google, both windows opened so, as it was still raining, I covered the car with a tarpaulin. The battery drained so I wasn't sure what had happened. Now with a charged battery , all sorts of things started to randomly operate. Finally, I discovered water under the left seat (it's amazing how much water that dip under the seat holds!) which seems to have damaged the ECU . I've removed it and taken it apart but corrosion has already started. I've cleaned it off and dried it but am nervous about trying to refit it. My question is: A used replacement and new replacements are all around the £400 - £500 mark. Are there any other options? The Cayenne 955 module looks almost identical (or at least the plastic box and connectors) and is available for anything from £20 upwards. Obviously these models don't suffer from water ingress like the Boxster , so replacements are not needed as often. Can any other ECU with the same connections be reprogrammed to work in the Boxster ? If not, what are my options? will a 987 ECU still need reprogramming and if so, How best should I go about this? Sorry for the life story but hope someone can help. TIA Simon

In the US this would be a covered comprehensive loss on your insurance policy. Maybe you should check with your insurer.

Hi Simon, I would be quite leery about trying a 955 body control module on a 987. While they're the same-era electronics, I suspect some customization is done to these to at least keep it in the body series (ie - a 997 module might be the same as a 987 module, but Cayenne vs Boxster is unlikely.) I suspect the reason they're expensive is they get drowned with some fair frequency. You have described the symptoms of a drowned rear body control module.. When you get it sorted out - there are several discussions here on how to clean and where they are - the drains for the 987 series. There are about 6 drains that must be kept clear. Not terribly hard to do, but really needs to be done at least every fall when leaves start falling. As a WAG - the drains in the bottom of the folding top well are plugged up, at least one of them. Some people use trombone brushes to clean them, some people weed-wacker line, and some people just compressed air. What you don't want to do is disconnect anything while cleaning them, that can happen and is a PITA to make right. As far as programming - actually - they do have to be programmed for the car. You need someone with a PIWIS to do this probably. The FOXWELL NT710 I'm playing with has a module replacement mode, but it has to be able to read from the old module and then it writes that info to the new module. I believe a PIWIS can reach into the module and set individual parameters. As Ric helpfully pointed out - if you can get it covered by insurance - why not pass the problem on to a dealer? Even if you have some deductible it's likely to be less money than trying to DIY.

Hey Don, could you point some of the 987 Cayman threads my way? Didn't know till your post that there are drains I've got to clean on the car.

Hmm, good question. I thought we had a thread here for it. [EDIT - deleted old link] We should probably make a similar thread here ourselves, and pin it as well! @deilenberger care to repost it here? [EDIT: He reposted, as noted below: https://www.planet-9.com/threads/lets-clean-those-drains.255068/ ] Incidentally, I know on my 987.2 I also have little clip-in screens that help prevent the gunk from getting into the tube. This makes cleanup a little easier, as the stuff stays at the screen. I just pulled it off, rinsed it off, wiped around the area, then put the screen back I also tested flow to ensure even a little water came out immediately from under the car.

Thanks for the info. Unfortunately my insurance excess (co-pay) is only about £100 less than a used replacement and will impact my renewal next year so I'm not going to be much better off.

Done.. https://www.planet-9.com/threads/lets-clean-those-drains.255068/

I'm so sorry to hear about this, @SimonR - Hope things get sorted soon. Can you list what errors kept coming up? That might actually help with a definitive diagnosis here. My strong guess is that the flooded box in question is your rear control unit, NOT an ECU -- which may be a game changer. I don't believe used rear control units cost that much on this side of the pond -- so you might want to look further. If you decide to risk tackling this yourself, I would absolutely make sure you do two things: (1) Get the exact box for your car -- meaning the EXACT model for your Boxster's year/model. Not a Cayenne, nothing else. (2) Then, use a PIWIS 2 to program it. It's definitely a learning curve to master that, but if you have more time than money -- you just might be able to get it to work. Tons of threads here on P9 for that; an indie wrench might be able to help as well. (3) If you think this might happen again, there are waterproof boxes out on the market made for this very purpose (underseat flooding) to protect the replacement module from getting damaged again. Cheering you on here, and do let us know how you get on. Hope this helps!

Thanks for your advice. I can confirm that the rear control unit was flooded. I removed it and cleaned it up with a solvent cleaner and dried it out. I've plugged it back in and now the rear spoiler has now retracted and windows operate as they should. The engine starts so is driveable. however, the roof does not open, not a squeek from the motor. I still need to check the rear trunk opening (if this is connected) and anything else that is controlled by this. This could be a problem if the motor has been damaged. The roof did try to open by itself enev though it was locked down when I connected the battery and before I had discovered the issue but the clam shell did close by itself in the end. I don't have access to a PIWIS 2 but there are places that can program a new unit. I have a basic Durametric diagnostic unit which may give me some insight as to what else is happening. I will post the fault codes this week. Unfortunately, i've not been well over the weekend so haven't been able to do anything that involves travel more than 6 feet from the bathroom! The cost for a second hand unit over here is a ridiculous £500 ($630) plus around £70 for programming it although I may be able to get one programmed and inported from Eastern Europe for around £400. Ridiculous when the Cayenne version can be picked up for next to nothing. I am prepared to buy a waterproof cover and take it off the road for the winter and sort it out when I can find a unit at a better price but accept that I may have to accept the inevitable. As far as a replacement is concerned. there seems to be enough room under the seat to raise it up a couple of inches so I may be able to make up something to keep it off the bottom and hold it securely. I'm semi-retired so definitely have more time than money!

When I got my Boxster , I had a similar situation, @SimonR -- If I was in your shoes, I'd probably do the following...but YMMV may totally vary as all this may be a huge gamble (as it was for me -- and I think my gamble ultimately paid off): My car's previous owner had already installed a replacement rear control unit, but he didn't know what he was doing. The car came with the spoiler stuck in the up position and I don't think the top would go up/down. Doing my homework, I reasoned that the replacement unit just needed to be reprogrammed. My gamble paid off, as it was indeed able to be programmed with a PIWIS 2 -- but learning all that was a project in itself (a worthy exercise, however -- as it has helped me with other stuff on my cars). If your hard top worked before the flood, your motor is likely just fine. None of it likely got flooded. Don't mess with your convertible top motors. If the current unit is all cleaned up internally and some things work, your unit may actually be okay and salvagable. If it was me and money was tight, I'd open the unit if possible, clean any corroded boards with 91% isopropyl (maybe contact cleaner), and reinstall it. I doubt it would blow things up, but YMMV. Next, I'd order a PIWIS 2 (read the threads here on P9). While you wait, learn how to set up your own virtual machine and master learning how to program it in demo mode. If you're not comfortable with that, have your indie wrench do the programming I wouldn't use a Durametric or the like -- as it might not have those advanced programming capabilities -- whereas a PIWIS 2 most certainly has. This way you could try (a gamble) to see if you could program it first BEFORE trying to replace the expensive unit. This may be all you need. If you really want a safe bet, bring it into your indie wrench (who has a PIWIS) and let them take care of it. Finally, I'd just address the leaks first. I didn't get a waterproof box (yet) -- I just made sure it would never happen again. My water drains came all trashed... Anyhow, I hope this guidance proves helpful! Cheering you on here.

Well the sun came out today, so I changed the wet cardboard under the carpet and hooked up my Duramatic and ran all the tests. I had already cleaned the board with some quick evaporating solvent cleaner I use for getting rid of bathroom silicone sealant residue. It may not have worked however so I will try isopropyl. I've posted the results below. Observations: Drove the car around for a while. PAS warning went away quickly. Rear brake light warning came on but could be a coincidence. Need to check this out. Roof still not working and when I release the catch, the windows don't drop a few inches as they normally do. However, the windows operate as normal and drop a fraction when I open the doors. Everything else seems to work as it should except the damn roof. Shutting the door after etc. but looking at a waterproof outdoor cover for the future. Anyway, here are the test results. The passenger (left in the UK) seat is not in the car so some codes may be linked to that. Thanks for your input so far and I hope these give an indication of the problem: PSM Current Fault Codes -------------------------------------------------------------------------------- C158 Communication gateway (CAN drive) -------------------------------------------------------------------------------- 4444 LWS No initialization -------------------------------------------------------------------------------- Airbag Current Fault Codes -------------------------------------------------------------------------------- 800B Driver's head airbag above upper limit -------------------------------------------------------------------------------- 8004 Passenger's thorax airbag above upper limit -------------------------------------------------------------------------------- C152 Communication timeout PSM Control Unit -------------------------------------------------------------------------------- C140 Communication timeout Instrument Cluster Control Unit -------------------------------------------------------------------------------- 8012 Voltage supply below lower limit AWS Current Fault Codes -------------------------------------------------------------------------------- Module failed to initialize Make sure the key is in the ON position. The vehicle may not have this option or there may be a wiring problem to the computer. This could also be a module that simply failed to respond. -------------------------------------------------------------------------------- PAS Current Fault Codes -------------------------------------------------------------------------------- 8003 Supply Voltage Clamp 15SV (SC+) -------------------------------------------------------------------------------- 8004 Supply Voltage Clamp 50 (SC+) -------------------------------------------------------------------------------- 8005 Supply Voltage Clamp S (SC+) -------------------------------------------------------------------------------- 8001 Supply voltage -------------------------------------------------------------------------------- C110 Comfort CAN -------------------------------------------------------------------------------- C102 Comfort CAN - single-wire operation -------------------------------------------------------------------------------- C131 Communication gateway (CAN comfort) -------------------------------------------------------------------------------- C121 Communic. rear control module PASM Current Fault Codes -------------------------------------------------------------------------------- Module failed to initialize Make sure the key is in the ON position. The vehicle may not have this option or there may be a wiring problem to the computer. This could also be a module that simply failed to respond. Gateway Current Fault Codes -------------------------------------------------------------------------------- C121 Communic. rear control module -------------------------------------------------------------------------------- C122 Communication driver's door control module -------------------------------------------------------------------------------- C102 Comfort CAN - single-wire operation -------------------------------------------------------------------------------- 8001 over/undervoltage Cluster Current Fault Codes -------------------------------------------------------------------------------- C121 Communic. rear control module -------------------------------------------------------------------------------- C141 Communication PCM 2.1 -------------------------------------------------------------------------------- C172 Fault driver's door CM -------------------------------------------------------------------------------- C173 Fault passenger's door CM Air Conditioning Current Fault Codes -------------------------------------------------------------------------------- 8001 Power supply -------------------------------------------------------------------------------- 8023 Outside air/recirc. air flap motor -------------------------------------------------------------------------------- C121 Communic. rear control module Veh Elec Sys Current Fault Codes -------------------------------------------------------------------------------- 8036 Passenger's front airbag stage 2 below lower limit -------------------------------------------------------------------------------- 8035 Passenger's front airbag stage 1 below lower limit -------------------------------------------------------------------------------- 8002 Passenger-side belt buckle switch resistance -------------------------------------------------------------------------------- 8042 Passenger's front airbag stage 2 incorrect coding -------------------------------------------------------------------------------- C121 Communic. rear control module -------------------------------------------------------------------------------- C122 Communication driver's door control module -------------------------------------------------------------------------------- C123 Communication passenger's door control module -------------------------------------------------------------------------------- C127 Communic. front control module Steering Column Switch Current Fault Codes -------------------------------------------------------------------------------- C102 Comfort CAN - single-wire operation -------------------------------------------------------------------------------- C110 Comfort CAN -------------------------------------------------------------------------------- 8001 Driver-side belt buckle switch resistance Front Current Fault Codes -------------------------------------------------------------------------------- 8042 Passenger's front airbag stage 2 incorrect coding -------------------------------------------------------------------------------- 8029 Passenger's front airbag stage 1 short circuit to B+ -------------------------------------------------------------------------------- 8017 Key switch circuit 1 implausible signal -------------------------------------------------------------------------------- C121 Communic. rear control module -------------------------------------------------------------------------------- C130 Communication steering wheel electronics (comfort) -------------------------------------------------------------------------------- C120 Communication vehicle electrical system control module -------------------------------------------------------------------------------- C122 Communication driver's door control module -------------------------------------------------------------------------------- C132 Communication air conditioning regulation Rear Current Fault Codes -------------------------------------------------------------------------------- Module failed to initialize Make sure the key is in the ON position. The vehicle may not have this option or there may be a wiring problem to the computer. This could also be a module that simply failed to respond. -------------------------------------------------------------------------------- Left Door Current Fault Codes -------------------------------------------------------------------------------- 8888 Mirror vertical potentiometer -------------------------------------------------------------------------------- 8887 Mirror horizontal potentiometer -------------------------------------------------------------------------------- 8705 Door lock signal implausible -------------------------------------------------------------------------------- C121 Communic. rear control module -------------------------------------------------------------------------------- 8704 Door h. button inner sh. stroke -------------------------------------------------------------------------------- 8601 Door safety light/ door handle light -------------------------------------------------------------------------------- C131 Communication gateway (CAN comfort) -------------------------------------------------------------------------------- C102 Comfort CAN - single-wire operation -------------------------------------------------------------------------------- C132 Communication air conditioning regulation -------------------------------------------------------------------------------- C110 Comfort CAN Right Door Current Fault Codes -------------------------------------------------------------------------------- C121 Communic. rear control module -------------------------------------------------------------------------------- C102 Comfort CAN - single-wire operation -------------------------------------------------------------------------------- C131 Communication gateway (CAN comfort) -------------------------------------------------------------------------------- C120 Communication vehicle electrical system control module -------------------------------------------------------------------------------- C122 Communication driver's door control module -------------------------------------------------------------------------------- C110 Comfort CAN -------------------------------------------------------------------------------- C128 Communication PAS (comfort) control modue -------------------------------------------------------------------------------- C132 Communication air conditioning regulation -------------------------------------------------------------------------------- 8002 Passenger-side belt buckle switch resistance -------------------------------------------------------------------------------- 8001 Driver-side belt buckle switch resistance

What is your battery voltage? You might try clearing all the codes, hooking the car to a charger, and re-running the scan. There were a LOT of voltage fault references there. Does the tool (which is?) you're using read or ask for the VIN# before doing the scan? The reason I ask is the modules it couldn't connect up to. Most tools that ask for the VIN# then look up somewhere what equipment was on the car when it was manufactured.

Thanks. That's extremely helpful. I appreciate it. Unfortunately the tool only asks for the model but not the VIN. Mine is the 2005 2.7 with Bose , steering wheel controls and all electric seats (heated, full electronic adjustment etc.) Not sure how else it differes from standard as it's my first boxster . However, I'll charge the battery , clear the codes and run the tests again. I'll also buy some switch cleaner and have another go at cleaning the unit. I feel I'm getting slightly nearer!

Hi SimonR , Again, I'd strictly use 91% isopropyl alcohol. I would not use the solvent one you used - that sounds a bit harsh. I'd stick to isopropyl or very carefully -- a dedicated cleaner that is used for motherboards. That is a TON of fault codes. Again, I'd like to see what a PIWIS 2 sees (probably the same fault codes, though). If it were me and you're insisting on doing this yourself, I'm afraid that this isn't an easy fix. I'd really start reading as many threads as you can (and even watching a few videos) and learning how to use a PIWIS 2 as a tool. I'd mark down what errors you've got, clear the codes, and then see what new codes are thrown. Rule #1 of code reading, etc. -- ALWAYS plug your battery to a very powerful charger. You don't want to "brick" your car's computer. Most importantly, swapping out cardboard is NOT going to help much and you need to act quickly before the mold sets in. Whatever you do, pull that carpet back and please get some fans blowing...and keep swapping out the towels...while protecting it in a garage. In short, the carpet has a ton of very absorbent cushion material (like a sponge) underneath, that will trap the water and moisture. You can't see it. Trust me -- I've been there before. You'll need to remove the driver's seat and get in there. Once you're deep down, you'll see how wet it really is. It took me a solid week of drying out the car once I got in there. This should be your primary concern right now, as it's not just a little bit of water. If not completely dry, this could be the stuff of totaling the car, I'm afraid. Just my two cents from having been there and rescuing a car with water on the driver's side. Cheers.

Thanks for all the input so far and would like to wish everyone with a drivable Porsche , a very happy Christmas. I've been sick for a couple of weeks so haven't had a chance to do anything and the weather has been rubbish. I have been jamming cardboard under the carpet and have just bought a small dehumidifier and a fitted waterproof car cover (stable door, horse, bolting etc.) Finally got around to cleaning the unit with isopropyl alcohol, charge the battery up and try fitting the ECU again today but with the same results: Windows operate normally, but the roof doesn't open When I release the roof and press the button to close it, the roof closing warning comes up on the dash, but nothing when I try to open it. I have cleared the fault codes and run all the tests again with the following results. I also got all the vehicle data at the same time. C110 Comfort CAN and C141 Communication PCM 2.1 were pre-existing from a previous test several years ago: Motronic 7.8 (9X7) Vehicle Data -------------------------------------------------------------------------------- Part Number 98761861201 Supplier Number 0261208300 Module Number 00419100A722 Ignitions (Range 1) 3184 / 3131h Ignitions (Range 2) 68 / 3063h Ignitions (Range 3) 0 / 0h Ignitions (Range 4) 0 / 0h Ignitions (Range 5) 0 / 0h Ignitions (Range 6) 0 / 0h Operating Hours Counter 3135 Vin WP0ZZZ98Z5U700800 Type ID DME Control Unit _987EU400 Order Type 987311 Country Code C10 Engine Type 9625 Engine # -ýý Transmission Type G8701 Transmission # 27104 Radio Code/ PCM Code 0 Body Color / Convertible Top Color 39C Interior Equipment TG PSM Current Fault Codes -------------------------------------------------------------------------------- 4444 LWS No initialization Airbag Current Fault Codes -------------------------------------------------------------------------------- 8004 Passenger's thorax airbag above upper limit AWS Current Fault Codes -------------------------------------------------------------------------------- Module failed to initialize PAS Current Fault Codes -------------------------------------------------------------------------------- C110 Comfort CAN PASM Current Fault Codes -------------------------------------------------------------------------------- Module failed to initialize Gateway Current Fault Codes -------------------------------------------------------------------------------- 8001 over/undervoltage Cluster Current Fault Codes -------------------------------------------------------------------------------- C141 Communication PCM 2.1 Air Conditioning Current Fault Codes -------------------------------------------------------------------------------- No fault codes found. Veh Elec Sys Current Fault Codes -------------------------------------------------------------------------------- No fault codes found. Veh Elec Sys Current Fault Codes -------------------------------------------------------------------------------- No fault codes found. Steering Column Switch Current Fault Codes -------------------------------------------------------------------------------- No fault codes found. Front Current Fault Codes -------------------------------------------------------------------------------- No fault codes found. Rear Current Fault Codes -------------------------------------------------------------------------------- Module failed to initialize Left Door Current Fault Codes -------------------------------------------------------------------------------- No fault codes found. Right Door Current Fault Codes -------------------------------------------------------------------------------- No fault codes found.

What tool are you using to read the fault codes? If the output is like I suspect: device tested name Current Fault Codes -------------------------------------------------------------------------------- codes A B C D, etc.. Then the code for the rear module: Would seem to point to the flooded module being kaput.

The tester was just a cheap OBD II unit and is OK for simple tests. It helped me diagnose a missfire a few years ago. While I'm pretty sure, as you say, the module is trashed, I will try and get the car on a proper test machine for a full test. At least the test I ran gave me all the car's details as one supplier will program the replacement module based on the VIN which will save me around £75. Thanks for your input.

Hope you feel better, Simon! What a drag this time of year. Yes, you'll want a proper unit (ie, PIWIS ) to really see what's going on and to ideally reset things later. Finally, the moment you feel better, please -- pull back that carpet if you want to keep your car and squeeze out the moisture. It's a bear of a job but it's vital. You'll never quite be able to get the odors out and it'll be ruined if there's mold already starting. Cheers and Happy Christmas!

Fortunately, while some of the leather was showing a little mould which cleaned of pretty well, the carpet seems unaffected apart from being damp and it's only on one side at the back. There is no smell so far. I've jammed cardboard under as much as I can and am changing it regularly. The big sponge block is now dry. The small dehumidifier removed about a pint over night. It's been quite mild recently (10c - 50f) but quite rainy but hopefully it should all dry out. I'll also get a hair dryer on it but may have to wait until my wife goes back to work on Wednesday so I can 'borrow' it! I'm happy to keep it off the road for another month or two anyway which will give me time to get things organised. Hope you have a good break.

One other thing that you may want to do is to raise up as much of the carpeting - prop it up to expose the foam - and put in a fan to move the air and let that dry. Hopefully, that might aid in the drying process. Again, good luck with this and cheering you on from the other side of the pond!

Hey Simon, I have a 987.1 Cayman that lived a flood life. The rear body module under discussion behaved much as you've described. On inspection the circuitboard looked like an old pizza. I replaced it with a used unit from a 987.1 boxster . iirc I used my durametric to make it match my car's config. ie no, I don't have a convertible top! All has been well since 2018 - meaning my spoiler works, hatch opens and the battery isn't drained by reverse lights when there is no key in the ignition and the car isn't in reverse. That's my experience. Cheers, Pete

I had a very similar experience back in 2012 very soon after I purchased my 2007 Boxster . I drove from MA to WV and had to park in a field when I got there. My 2 week stint was just about up when I decided to visit my car a couple of days before I was planning to leave. The field was not level and that combined with at least 1 plugged rear drain on Boxster did the damage. When I got to the car, the windows were all 1/2 way down, both the trunk and the frunk were popped, the clam shell was 1/2 open, the spoiler was up and the battery was completely dead. The huge storm that had dropped all the rain happened 2 days after I arrived so the car had been sitting open for over a week. At least I was able to get the battery out without going through the fuse box terminal routine. Needless to say I was horrified at the condition of my relatively new Porsche . I took the battery back to where we had a charger and fully charged it. As you can guess, putting in a fully charged battery only opened a new round of problems. I knew very little about the location or function of various ECUs or even why all this stuff had happened. I got the car started with lots of warnings flashing at me. As best as I could tell, most of the rear of the car was electrically out of commission and the roof would not move. It was running well enough that I thought I could make it to a friend's house in MD that was near a Porsche dealer. After getting on the road and other than having to travel with the roof closed (1/2 the fun of these long trips is driving with the roof down) the car was behaving very well. I did discover that all of my rear lights including the brake lights were out however so I made the last hour after I discovered that much slower and using hand signals. I took the car to Porsche of Annapolis and they were amazing. They explained exactly what had happened and gave me options as to what to fix first and what I could afford. They replaced the rear ECU which had been flooded and dried out the carpet. They showed me 3 other Boxster interior carpets being dried out for the same reason. The next day I was in much better shape to complete the trip with everything except the roof working properly and a much better understanding of my car. When I got home my home dealership replaced the nylon balls on the roof system that had broken when the roof tried to open during the storm but couldn't because it was latched. This was a very hard lesson but I learned well and twice a year I clear all the drains. I also purchased a set of the drain screens they started equipping newer Boxsters with and those provide me with less anxiety and easier cleaning of the drains. I have not had any flooding issues in the 11 years since. I love the car and will likely keep it until I can't drive any more. I wish I knew when I bought it what I know now about how it works. But that is what these forums are about. 1. Dry out the interior of your car. It needs to be moisture free before you take other steps 2. It worth a try to clean up your rear ECU but don't count on it working. You do need a good ECU specific to your car in order to safely drive. I found it fast and easy to have a dealer do it, you have to determine what works best for you. 3. There is enough information available through the forums like Planet-9 for you to repair the soft top and get it working properly if you are al all handy. If not, the dealer can do it fast because they have all seen it before. 4. To this day, I still put an outside cover on my car whenever there is a major rain storm predicted.

Thanks for your support. My small and cheap dehumidifier is working well. It's only sucked about 2 pints out in a week but after 2 days ignoring it, there was no mould on the leather today and the carpets only feel a bit damp. I propped up the carpets and put a couple of 2x1 timbers under to allow air flow and today, put my wet and dry vaccuum on blow with the tube under the carpet. After 30 minutes, the interior was nice and warm. I'll keep this up for a few days until everything is dry. My new waterproof cover ( nenyan Custom Car Cover Waterproof Breathable Fit Porsche Boxster (987) 2004-2012, Outdoor Full Cover, All Weather Protection Durable with Zip and Cot ) from Amazon arrived on Christmas eve. I'm very impressed considering the cost (US$166). It even came with the zip on the UK drivers side. The wind has been blowing around 50mph for the past 5 days and it's still attached! obviously ,had I bought it a couple of months ago, I wouldn't have had the flood. Next thing to buy a new module and I should be back and running. Then I need to sort out the brake pipes, water leak in the front radiator and get the wheels refurbished. Then fix the bend in the front hood and a respray. Why did I think owning a Porsche would be fun?

Wow, deja vu . I feel your pain. My own 2005 Boxster underwent a remarkably similar experience. I wound up replacing the water-damaged control module with one from ECU Doctors in Florida, which also programmed it to match my car (they're not generic). It solved all the electrical problems you describe and the car is now 99% fixed. Once you get everything dry, and fix or replace your control unit, it might then be time to examine the left and right gear-reduction units (aka transmissions) that physically raise and lower your convertible top/roof. In my case, the water-damaged control unit tried to force the top open while it was latched shut, stripping the gears in the transmissions. If it becomes necessary, you can either replace the transmissions as a unit (expensive) or open them up and replace just the stripped gears (cheaper but messy). Either way, we're with you!

Thanks for the encouragement. I've just ordered a replacement unit and it's been programed to the VIN so I'm hoping it will work. It's coming from Slovenia but it's over £100 cheaper than one from the UK and he's programed it in the price. Yes, my roof tried to open by itself as well. I think I managed to disconnect the battery quite quickly as the front bonnet (hood) was already open. If not, it can wait until the weather improves. It's been blowing around 60mph for what seems like 2 months! I'm fairly happy tinkering (I managed to change the convertible roof by myself, the plugs and coils, brake disks, pads and shoes and even changed the air filter which was a lot harder than on my Skoda . Anyway I'll report back once I've fitted the new module. In the meantime, I'll start looking for roof gears just in case!

A great tool for cleaning the drains holes, is a trombone pipe cleaner. Very in expensive and does the job, top to bottom. Got mine thru Amazon <$10.

Amazon realized cleaning drains is a thing - and they now sell what looks like trombone cleaners as "Drain Cleaning Brushes" I think this will get you to it - if not search "Sunroof drain" and a bunch will popup. Amazon.com