Hello everyone, my first post here and I desperately need help. I bought this fun
Porsche 987
, drives very strong and reliable. However, I have no history of the last owner other than him going to jail and forfeiting the car at auction, money laundering I guess. Anyway, The speedometer does not respond to speed, and I have a check engine for "Vehicle Speed sensor", but it actually relates to advanced diag code of U0129-04, p1614-04, p0503-04. Essentially those all relate to no communication with speed sensor/ PSM. I have attached photos. My guess is there was a millage blocker installed, in a ghetto way. I looked behind the dash and there is nothing plugged into the harness. All wiring looks OEM. My only clue is there were clearly some soldering done with the OBD wires, and a previous spark that melted the harness. I also found an untouched wiring bundle with melted insulation. ( I suspect that was when my dad installed a battery backwards a few months ago ) Attached are photos. I have tried to get my speedomoeter back with countless hours of work and research. Really hoping some one can help me understand the pin out of OBD harness and if it was tampered with to block miles/ speedo. and how to restore to OEM. Luckily based off carfax, the car has not moved since last owner had it, they took it about a month after he bought it, car sat for 1 year during his trial. so miles are accurate , but I want the car to be restored to OEM. thank you in advance im moderately knowledgeable with mechanics so very willing to dive in and fix it.
Hi Joe - welcome to Planet-9, the Friendly
Porsche
Forum!
A few things on posting here:
Please break up your post into logical paragraphs. It appears now as a single block of dense text. That turns people off, and lots of people won't bother reading it.
Please remove the duplicate photos, they will also annoy people. It's usually better to embed full-size photos in your posting so people don't have to click in and out of windows to read your text and view the photos.
Please ALWAYS include info on what car we're talking about. Year, engine, etc - anything special. I figured out you have a 987.1 Cayman by looking at the diagnostics tool photos..
That's all about making it easier for the people you're asking for help to help you. "Better questions get better answers" (me).
OK - on to your problem.
Yes - I agree - you're unfortunately in a world of hurt with what's been done to your car. Not only has the OBD-II port been hacked up for some reason, but there are also loose wires dangling around, other wires spliced into the harness at the relay box, and a single auxiliary fuse hanging around the back of that box. OUCH!
And the car has suffered the battery being connected backward disaster.. that can cause all sorts of ugly issues.
You mention you're moderately knowledgeable with mechanical things.. but no mention of electronics, which is a completely different skill set. In this case - you need two things:
A set of wiring diagrams so you can track down what wiring should be there
Someone knowledgeable in electronics. These people are getting harder to find since a lot of that skillset went off-shore. It used to be you could ask around and find some "ham radio" guy who knows which end of a soldering iron to hold, and how to do continuity checks, and voltage checks, they might even have an oscilloscope. These guys are all my age now, and they're dying off. Chatting on the phone seems to have killed ham-radio. And the skillset isn't learned easily or overnight.
#1 can be solved. The latest version of AllDataDIY for the 987 series has some excellent diagrams. Unlike earlier versions, these can be expanded in size on your computer screen and remain readable. I believe there is also a component locator that will help you identify what you're looking at. Somewhere here - we have a link to a discount program AllData offered, I believe it's still valid. A search might turn it up (I posted it.. so searching on me might find it for you.)
#2 is the problem. Most mechanics are not electrical engineers or ham radio operators. Electronics to them is a plug-and-replace scenario. They hook up the PIWIS, it tells them XYZ module isn't working, so they replace it. If that doesn't fix it - they look to PIWIS to tell them what else they can replace. It won't tell them what wires have been damaged or shorted or are open-circuit.
They won't want to go near your car's wiring because they have no idea why and how it was hacked up by the former owner, and they have no idea what car modules may have been damaged by the reverse voltage incident with your dad.
So - what to do? If you lived in NJ, I do have a friend who is an exotic car mechanic with a degree in Electrical Engineering, and he's also a ham-radio operator. Electronics is his hobby, it used to be a job too - he taught it at the Army Signal Corps lab at Fort Monmouth NJ. He's an exceptional resource for this sort of thing since he actually enjoys doing this sort of troubleshooting. And he's very good with it.
I have no idea how you might find such a person wherever you are.. but perhaps being a member of the local Porsche club chapter might be a help - asking the club members who they'd use might turn up someone who can help.
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Some clues that might help...
- What diagnostics tool are you using (it doesn't look like one I've used)?
- Does the diagnostics tool have Porsche SPECIFIC functionality - ie - can it access the modules in the car?
- The AllDataDIY has charts listing the actual Porsche definitions for error codes. Any code starting with U or with a code "bigger" than P0999 is a Porsche-specific code, and most OBD-II code readers have no info on them or wrong info on them. Knowing what Porsche codes these really are might help narrow things down.
If not - that's the first thing to purchase. I'd suggest a Foxwell NT530 with the Porsche software, it's around $160.
The reason I suggest this tool is it allows you to monitor signals going into the various modules in the car. Somewhere your speed sensor signal is getting lost. That signal comes from one of the wheel speed sensors, probably by way of the ABS/PSM module in the car. The Foxwell will help confirm if the signal gets to the module and if the module then sends it along to the speedo. Using this tool might narrow down the area to look for a problem. The wheel speed sensors on these cars are known to fail sometimes, and it might be something as simple as that..
Some of the messages you're seeing can be caused by the installation of an aftermarket radio. The stock PCM is part of the communications chain in the car, and there will be error codes stored in various places if they can't find a PCM t talk to. Those codes are harmless and can be ignored.
I'm sorry there is no magic here. You're in an uncomfortable position, but I assume you got a really good deal on the car.. usually there is a reason for those sort of deals, and sometimes the deal doesn't really turn out so great.
Please DO keep us up to date on your progress.. it's a challenging problem and all of us can learn something from how the fix is achieved.
