P0129 - Barometric Pressure Too Low

The only fault code showing with the tools we have is: P0129 - Barometric Pressure Too Low Does anyone have any experience of this sensor or advice on correcting this issue. Any help appreciated. Cheers Spart

Quick reply .. its part of the dme so not good news .. i'll investigate and see what i can come up with . EDIT There is no diagnosis .. it's a replace the DME if its a permanent fault . The car needs to know this signal to work out altitude and therefore adjust the fueling accordingly. At a guess and as the car knows its faulty it would default to sea lvl so in theory won't cause any issues unless you go to higher altitudes .

Many thanks Iain, That's a *****....I suspect that having to replace the DME would then need either Porsche or a Specialist would need to program a used module with my cars Immobiliser key codes etc. Otherwise I guess it would not run! There was no DME fault reported by Cridfords on their original list of car issues that I got with the car. I was hoping it was a simple sensor..... Are they interchangeable with the Boxster 986 units? I can see few used ones (new ones are uneconomical) in the hundreds of pounds. Lots being sold complete with Immobiliser 2 x keys and ignition lock. I guess I could swap the actual Key blade out of the my existing fobs to avoid having to replace the ignition key unit. Cheers Spart

The usual route of dme , alarm control unit plus key fobs would be the cheapest way out . These are usually Boxsters though due to the water ingress problems and a market for these kits . 996 afaik will be different .. 996 isn't a boxster after all ... I think for now .. fix everything else and see how it drives .. my hunch is it will fail to sea level by default and as such be fine unless you go up a mountain .. in that case it will run rich . Fuel trim values after a few drives will soon say .. we can see if its running rich or weak from these .. although you will need a tester to read actual values . Feel free to send me any values at that point and i'll do my best .

Thank you Iain, It runs superb and is a joy to drive, long time since I had a 996 . I have just got Torque working on the new Head unit so will set logging on and see what that can see. I don't know if the laptop and old version of Durametric will provide anything over and above what the OBDLink adaptor and Torque would provide. Would Porsche or a Porsche specialist be able to code a used DME unit to my Immobiliser and fobs? Avoiding having to replace the M535 Key Fobs etc. Something like this: https://www.ebay.co.uk/itm/Genuine-...344435&hash=item4d73aaaed3:g:0kkAAOSwm8Na-r4R Part number shows as: 996 618 604 00 control unit - dme - see technical information GR.2 NR.8/02 Model Years 02- Qty 1 Model M620 Cheers Spart

To code .. in theory as its changed with software over the years .. then you would need the Immobiliser code from the donner vehicle then the immobiliser code from your car to code the new .. or rather second hand dme onto your car ... both come from OPC and you have to prove ownership . In short .. if people on ebay sell a used dme .. it must have the immobiliser code and it must work so can be coded .. if not they would be selling junk and i think would soon be closed down . For me .. leave it for now .. that's all i can say .

Ok cheers Iain. Thank you for your help. Spart

If the sensor is on the main board I would look at the possibility of changing it. It will quite possibly be a standard part. Nothing to lose. MC

So take the DME unit apart? Solid state sensor mounted on the board? Sounds scary for a non electronics guy.... Cheers Spart

If you have resigned yourself to it being swapped, send it to, I'll take a look for you. MC

JMG Porsche to the rescue! I just though I would update this thread with the results of fault finding and first stage resolution. The fault according to Porsche is only cured by replacement of the DME. This is because instead of Porsche using outboard sensors that are easily replaced (MAF Sensor etc.) the barometric pressure sensor is a solid state device located on the main board of the DME. This means that the DME will have to be replaced! This potentially opens up a can of worms for the amateur maintainer as it would normally require Porsche to remove the old DME, Plug a new one in and reprogram the new one with the correct software for your vehicle and the correct IPAS codes for the immobiliser system to ensure we get fuel and a spark. If any of you have checked this would relieve you of a couple of thousand pounds possibly more. A very clever guy called Jon Mitchell who is the Managing Director of JMG Porsche has another solution. JMG are a very long established and respected Independent Porsche Specialist. Jon got fed up with this situation after one of his team inadvertantly 'bricked' a unit. Knowing that there was a conversation going on between the Immobiliser (typically M534 box under your passenger seat) and the DME either under your driver seat or next to the cab hydraulics on a cab. Jon set out to understand what was going on. This conversation was shrouded in mystery and the subject of many many 'how do I get around this' type of threads on this and many other forums. After many thousands of hours he finally decoded the secret language between the components and built a test bench where your immobiliser and DME can be plugged in. He can then read the magical codes from your components that allow programming of a DME, immobiliser, keys etc. He can test the operation of your Immobiliser and DME combination with your keys and ship back to you. In my case I had to find a new DME, there are many 'sets' out there on the internet. Many from boxsters and a few from 996's. Typically these are a combination of M534 + DME + 1 or 2 keys if your're lucky. Prices vary wildly from a few hundred pounds to over a thousand. Provenance of these units can be problematic. They are sold in sets to avoid the issue of the DME not being matched with the correct VIN and IPAS codes to unlock the fuel and ignition system. You would normally have to replace your old DME Immobiliser, keys etc. In my case we don't believe there is anything wrong with my Immobiliser and keys etc. as all functions seem to operate perfectly. Just need a new DME to clear the P0129 fault and allow us to continue our project. Jon is able to lift the programming from my malfunctioning sensor DME and reprogram a replacement DME with my programming and the correct IPAS codes and VIN for my car. He is probably the only person capable of getting IPAS codes whilst the Porsche world is in lockdown, as he is able to read and decode them from the components. All of this is in his publicly available primer on how Immobiliser systems and 'the conversation' works elsewhere on this site and on the great articles on the JMG Porsche Website. Interesting reading. You will of course need to provide full ownership and credentials for the components and their corresponding vehicles that Jon will be working with. For credibility Jon is theTechnical advisor to the Porsche Club of Great Britain and the Technical advisor to The Independent Porsche Enthusiasts Club and a thoroughly nice chap I located a matching part number, year and model of DME from a specialist breaker who was able to provide full details of the Donor for checking and verification purposes. So where are we now? We stripped out our components and the full interior at the same time as we are going to fully refurbish it. On their way to Jon via insured courier are all my components. I suggest you insure the package for £2,000. Jon will receive my old DME, the replacement DME, my M534 Immobiliser unit and my 2 keys. Once Jon has performed his black magic and assuming all goes well. It should be a plug and play exercise when I get them back. Just for fun afterwards and of course for learning purposes I have agreed with Martin (MisterCorn) that we can pull the old one apart and look at the possibility of replacing the failed sensor chip. I am intrigued to have a look inside, Martin as most of the readers of this subforum will know is a bit of an engineering and electronics whiz and is in the process of completing his C4 project car http://911uk.com/viewtopic.php?p=1537897#1537897 . That if you have not read this thread I would say is required reading for any enthusiast of this model. It will be an amazing vehicle once complete. It was a fascinating thread to binge read I would like to thank DeMort and MisterCorn for their help, advice and guidance in troubleshooting this project car. Tune in for the next instalment - When The DME and Immobiliser Returns..... Cheers Spart

DME Immobiliser and Keys Back So Jon at JMG Porsche returned my old damaged DME (now with MisterCorn) and the newly reprogrammed replacement DME and my keys and Immobiliser unit. They were great to deal with and Jon is clearly Yoda level ont his stuff. Plug and play re-install. Re-connected battery and went through battery reconnect procedure. All worked perfectly. We managed to reset and clear all old fault codes that have been there for a while. These were from before we replaced all the control units and modules. Reset Airbag light etc. Vehicle checks out and we are only left now with the Engine Oil Level Check Failure issue. Diagnostic says Oil Level Check - No signal received. So this is the last piece of the puzzle for us to restore this vehicle to its former very clean state. Not sure where we go from here. Replacement cluster seems likely, expensive to test the assertion that it is a logic problem in the cluster. Does anyone know if I can use any cluster with M249 compatibility? For instance a C4 or C4S Tip Cluster from 2002 as mine is a cab does that matter. Parts cat would suggest not. I don't think from the wiring diagrams that the cluster is doing anything to control any modules. Just reporting. My part number is 996 641 106 02 It has white clocks. Parts cat would seem that there are many clusters that have the M249 option from MY02 or later. Could I maybe use one of them. Hopefully someone a lot more knowledgeable than me can comment. Cheers Spart

When I had issues with warning lights 9Excellence reset the car and the problem went away. Initially I was expecting to have to replace the cluster and new ones are £*,000s. 9E told me that they have a reliable supplier in Yorkshire who can repair faulty units for about £200.

Thanks for the info I will call them. We are going to do a service replacement procedure on the cluster and remove it. Then re-install it as if it were a new replacement. Then code and program it as you would in a real replacement situation. Then do a full handover scan of the car. That is once we get our PIWIS II laptop repaired! Cheers Stephen