When the lights of the Porsche 958 Cayenne malfunctioned, How to use the piwis tool thorough visual inspection.
Let’s hone in on what stood out most from PIWIS diagnostics:
1. The overhead console is a subsection of the rear electronics module, but the overhead console part number could not be read. Possibilities that occurred to me: Cable missing / wrong; One or more wires are grounded; Back BCM was replaced but incorrectly revised or incorrectly coded; Rear BCM has been replaced but needs to be linked to the car using the dealer’s online coding; Overhead console is somehow seen but needs to be taught Assessment: The rear BCM is unlikely to fail or be removed – even by a savvy thief – therefore unlikely to have the BCM replaced. I was able to control some functions of the rear BCM via PIWIS, so it is probably coded correctly. I checked that all the wires were in place except for the alarm horn wire, but no signs in the harness that it had been cut. Let’s focus on the idea that the overhead console cannot communicate and let’s see which cables it shares with the BCM.
2. The rear electronics board has an error: communication with the LIN bus. Possibilities that occurred to me: Missing wire; Wire is damaged; Wire is earthed; Board is bad; The circuit board is coded incorrectly. Possible options for PIWIS troubleshooting: Short circuit to B + / ground or interruption in the line. , Communication aborted due to bit error. Evaluation: I opened the module and visually inspected the board for burn marks or melted components. I also visually inspected the wires after pulling the cable trays out of the connectors. They have tiny tiny numbers printed on the ports, trays, and sockets that need to be aligned. I only have a few hours a day to work on the car, so I ordered a replacement roof console for $ 70. I can always sell it when I don’t need it. It included the plugs hacked from the wiring harness and those plugs later came to the coupling.
The console arrived yesterday so I connected to PIWIS and got the same errors. I couldn’t teach this overhead console either. This result also indicates that it is the wiring. I’ve read all the wires for the rear electronics module for relevance:
Terminal 33 on connector A is titled LIN 1, which according to PIWI cannot communicate. If I scroll down I see that the black / yellow wire spliced a couple of things together.
We can see that the splices on that LIN1 wire from rear BCM are:
-Pin 5 on the panoramic roof connector (visible in roof console cavity)
-Pin 1 on connector A of the Sliding Roof (no idea where this is)
-Pin 12 of connector A of the Roof console
-Pin 2 of connector A for the interior mirror (rear view mirror).
I set my multimeter to resistance to tone the wires. I know the position and will check if they are connected. I used a wire isolation penetration probe on LIN1 on the BCM connector black / yellow (if you don’t have one you should get one). Sure enough, they are all connected, ringing and registering ~ 1 ohm. I see what the resistance to ground is (expected to be infinite, also known as an open circuit) but the meter rings and says 60 ohms! Might be into something here! I see in the circuit diagram that the BCM has a LIN 2. I try to tone that with bulk and get an infinite resistance.
Next, I wanted to run the wires right again. I didn’t want to cut factory wires when I had to because there isn’t a lot of slack and I don’t have a lot of my proper tools with me. I just had a 5 euro port freight cheap O crimping tool set. Three of the four wires I want to replace are the same type of pin; Coincidentally and conveniently, thanks to the plugs of used eBay items, I have a lot of reserves of these wire strands that have already been crimped to 4 inches. I pull out the factory pins in question and run my own wires. The small pins are relatively easy to remove with a small flat head or pick tool.
For the bigger wire with bigger pin in the panoramic roof connector I used my VW pin removal tool that I bought for changing the fuel flange plug on the 955 CTT.
That way I could connect the plug, but not the cable with the mysterious mass on it. On the other side of the connector, I just slipped a spliced end of my ghetto harness.
I double checked my work… popped in the key… and the dome light sprang to life! Great sign! I connected PIWIS and could read the roof console part number.
I had new bugs but probably because I couldn’t find the 5th wire in the splice so the sunroof still doesn’t work. Time to plan the route of my new wiring harness (of course I make it much nicer, safer, more protected and well labeled. Thanks again to those who followed and who had the idea. The experience makes you want a few dirt cheap Porsche or VW wiring harnesses with crimping pins in different sizes Sizes to aid you troubleshooting electrical systems in future adventures.