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By Niklas 71
Car: Cayenne turbo 2004, 250 000 km
The problems have been cascading over the summer, starting with a trashed rubber bushing on the cardan shaft support bearing. Before I got home and could fix that (thanks to a great description found in this forum!), the PSM and ABS lights went on. I guessed it was caused by the occasional knocking and wobbling of the cardan shaft.
After fixing the support bearing, the lights stayed on, so I bought an iCarSoft POR II to read fault codes. For some reason, it couldn’t pull codes from the PSM, but there was a fault code in the gearbox controller, about a lack of speed signal from the rear left hand wheel.
I gladly bought a new ABS sensor and replaced it, with no luck. I could remove that fault code but the lights returned and I still couldn’t pull codes from the PSM.
Next, I lifted the floor mats and found a lot of water on the passenger side from a blocked sunroof drain. Much of the wiring was corroded, so I carefully replaced it wire by wire. At the same time, I put in a new battery since the old one was really weak. The car started and ran fine, but the PSM and ABS lights kept coming back.
Next, I wanted to inspect the PSM, so I lifted the plastic cover beneath the wind shield and disconnected the DME in order to get down to the PSM.
The PSM connector looked fine without any traces of corrosion. The same was true for both DME connectors. I just brushed off some dust and put everything back together.
Here’s where my biggest problem occurred: now my car won’t crank the engine at all. When I turn the key, the instrument screen says that “daylight running lights are not active” or something similar. The cooling fans revv up to max but nothing more happens.
i have tried disconnecting the battery for an hour and then reconnecting again without any different behavior.
Any ideas on how I can bring my car back to life again?
Niklas in Sweden
Hoping to purchase this car.. They ran a DME and this shows only 19 Over Revs in Range 1 with none across the other ranges.. there are a "high"? number of misfires? Is this a concern or perhaps normal and maybe just require plugs / coil packs? My 1st Porsche.. I hope...
My first post here so please bear with me but pretty desperate for help. Have 2004 Boxster S and its, in general, running a bit rough (feels fuel rich). It also will also, on occasion, not go. Pulling up at a busy intersection and car reduces to Idle. Then put the foot down and the car stays at idle. Normally an engine restart gets things going again (although not always and sometimes requires a few goes).
Bought a computer reader and found error codes
P0102: Factory Fault code 115 - Mass air flow sensor - below limit
P2135: Accelerator Pedal - Signal Implausible
P0121: Factor Fault code 117 - Throttle value or accelerator pedal potentiometer - signal implausible
P1266: Factory Fault Code 409 - Fuel shutoff function monitor - signal implausible
Took the car to Porsche. They suggest a MAF sensor was the root cause and replaced it. It felt better for a few days then problem returned. They replaced another MAF sensor.. Same problem. They then said the MAF reads 0 and have checked the cables so its me DME and it needs replacing (not cheap)
Have taken the car back home and looked at the likely affecting values myself from the computer.
The computer shows to different values for MAF
Mass air flow (HFM) is always 0 regardless of if the car is working correctly or not and at any accelerator level
Mass air flow seems to move within a range of 18 (idle) to 100 (full throttle)
2. Throttle (since it had error codes on this)
Pedal encoder potentiometer 1 and 2 always move and the pedal value goes from 0-100% when its working but stays at 0 when its not. Since the potentiometers always move I am assuming the DME simply can't add things up so sticks the pedal value at 0.
ie. The MAF sensor reading above confuses the DME and it reduces the throttle to 0. That feel consistent with the behaviour of the car (its just sticks at idle)
Any one with any clues? Certainly don't want to replace the DME unless absolutely necessary....
LHD, Tiptronic, 1998 Carrera Coupe
Hi all, new to the forum but I was consulting some existing threads in the public forums regarding similar and related issues before I started an attempt at this job. I have access to the full wiring diagrams for the vehicle, the pdf is "996 Wiring 1999-2000.pdf" and can be found on google. I had them printed out on large sheet paper so I could trace the wires and go through all the possible issues without having access to factory scanning tools. I'm an electronics and industrial instrumentation technician hoping to build more work experience and reputation in order to get access to more of these repair gigs in the future on higher model cars.
I am working on a 1998 Carerra (Japan market) that was installed with a 'fancy' alarm system that sat on top of the existing setup and most of it was removed prior or at delivery, and I spent yesterday inspecting and repairing the wiring harness from the hack job that was previously in there. Today I went through the troubleshooting steps in order to eliminate probable causes of a no-crank.
The current owner had ordered a new ACM (alarm control module) and had it re-programmed and had told me the porsche dealer said to him the reason it won't start is a 'wiring problem' which I believe I had repaired all the wiring so far in the vehicle. I still have the old ACM with the car, it's just un plugged in the front storage. After doing my troubleshooting today, I believe it to be the DME but my lack of understanding how the modules interact I'm not sure if it defective or just needing to have some re-programming of some sort which may require a porsche scan tool.
Here's a take-away from my notes today;
Check for B+ signal from ignition start to pin 30 on START LOCK RELAY SUPPORT REAR when ignition key set to START. B+ present
Jumper pins 30 and 87 to test the relay is working. Turn ignition to START and check for engine cranking. Engine cranks.
Check for B+ from pin 86 to the relay coil. B+ present
Ground pin 85, and turn ignition to START. Engine cranks. Relay is working.
Check for current path from pin 85 on the START LOCK RELAY SUPPORT REAR to the DME connector pin 66 ACTUATION START LOCK. YEL/VI/BR wire. There is a path. PIN 66 on the DME is not switching to ground, and this won't let the car crank and start.
Check for path of ground from DME pin 68 START LOCK to the shifter PARK and NEUTRAL. It grounds in each position, open in any other.
Check for B+ on pin 88 on the DME which is the DIAGNOSIS W LEAD, and the only wire from the alarm leading into the DME. From my understanding of the alarm system from reading the description of operation from my ALLDATA catalogue, there must be some sort of handshaking going on between the RFID in the key fob, the correct serial and cypher in the ACM and the DME in order for this pin 66 to ground to let the car start.
Checks at 7.37V with the DME dis-connected, and 8.34V with the DME plug end connected. I also ohmed out this wire 0.2ohm to check for any unusual resistance because seeing that voltage struck me as unusual. Again, I'm not sure of how this system interacts but I can only assume it's correct as I also tried to measure this voltage with the spare ACM installed with the same reading.
What I wanted to ask for;
Is this a wiring problem, problem in the ACM or DME and what would have to be done to rectify it.
Warm regards, Aurelius
Attached are three helpful photos of the DME ACM and a sheet that I believe came with the new ACM
I've been all over the internet looking for basic information on the 981 DME. From what I've read it's manufactured by Continental. I'm an electrical engineer and really just interested in learning more about it in general. Does anyone know where I can find out some additional information about the DME such as pinout, processor, flash size, ram, etc..Also is there a diagram of the various controllers used in the Cayman S? Thanks in advance!