JebLacey

Hey everyone... I have been absent for a while. The box is in Tallahassee FL, Capital EuroCars. I spent about another 4 weeks troubleshooting, trying to confirm that I had the right idea, and all I have says yes... DME intermittant failure. Another key is that when I pull the DME off and shake it, there is something rattling inside. Is that normal (for you techs out there). Anyhow, having the DME replaced. Had to call PNA to get that jumpstarted. I must admit, I like the people at Capital Eurocars. They have had their hands tied, since they ahve been unable to recreate the problem every time i take it to them. I understand that that isnt their fault, but I went to PNA anyhow with the info I had and I think it is going to get taken care of. Just wanted to say hi and give an update... BTW... drove a 996... thinking of crossing over. any advice? Money is an issue, as we are starting another business right now, and most of our financial effort will be going there, but I am smitten... I must admit. Any MY or options to stay away from? Anything a must have? Brian

Thanks for the reply, Wardhog. Yes... I have checked the relays for function... its not just the fuel pump that does not get power... its everything that comes off the DME for its power or signal to start. At first, I thought it was the DME Relay, but that was eliminated due to the power in Pin 26 or 27 (one goes through the relay, the other is a straight shot from fuse C1) of the DME connnector.

Ok... I think I have conclusively determined that my problem is my DME intermittantly failing, as some of you have speculated. it is covered under the 8/80 emmisions warrenty, and the car is going to Tallahassee on tuesday. However, I am nervous, because with the holidays, bank account is looking rough. If they determine its not the DME, I am screwed. Please review my determination, and let me know if i missed anything. 99 Box, 63K miles, Tip. Symptoms: No start condition, CANBUS malfunction, no CEL test at ignition. INTERMITTANT problem. - Cranks, but no fuel pump start, no CEL, ect. My determination is that the DME is intermittantly failing, causing a CANBUS timeout when the car is in motion. If it fails to start after a successful, driving cycle, the CANBUS failure does not occur. The CANBUS failure occurs because the DME is sending power to the Unit, but then when it goes out, the TCU still has power but no signal for a second (all it takes is a faulure of a fraction of a second to cause the timeout). The CEL gets signal and power from pin 8 of the DME. There are only two possible causes for a no CEL condition at accessory... a failure at the bulb or wiring, or no signal from the DME. Since the condtion is always coupled with a no-start (ie other failures of units getting their power form the dme), i know that the DME is not sending the signal to its periphials. The DME gains power from the battery through fuse C1, through DME relay 1, to pins 26 and 27 of the harness. Power is constant on these pins, and has been verified w/ multimeter. No problem to this point. The ignition non-constant power comes through B8, directly to pin 56 (terminal 15) when the ignition is on. This power is also making it to the DME. The grounds at GP 8 and 9 have been tested, and are working as required. So essentially, the DME recieves all the power that it requires, but when the problem occurs, it does not send that power to the units that require it. The fuel pump relay, for example, does not recieve juice when the DME is down. No codes except the P0600 can be read (DTC 100-101). This is because the DME is not on to record any faults. The P0600 (DTC 100-101) only shows when the car is on and running before and during the faulure, so the TCU has a moment to store the DTC. Please let me know if anyone disagrees with my conclusion before I screw myself over in tallahassee...

when you turn the key to accessory, is the CEL test on? If the fuel pump isnt kicking on, with no CEL, check the connections to your DME. Start at fuse C1 and B8, move on to the relay in pos. 1, then check pins 26, 27, and with the key on, pin 56. I have the same problem. The car cranks but doesnt start... let me know if you are have no CEL, and I will elaborate as to how I get mine started... essentially, reset the DME by unplugging it. It will cause a CANBUS fault, but it may start. Also, look at the harness going into the DME for damage. One last thing tht worked for me for a while was simply disconnecting the batt for about 1 mike, then reconnecting, and wiggling the key seemed to help once!

Does anyone have a step by step on this one.... I have looked at the door, and it looks more difficult then the last one i did (SType Jag). Drivers side on a 99.

i have located the electronic humming sound... it seems to be coming from the Idle speed adjuster attached to the throttle body. Should this be humming LOUDLY while the key is turned to accessory? Also, just as a side note, when the car wont start (no CEL at accessory), the humming from the ISA is not present... ie, it is not getting any power. Could the ISA, if it is bunk, be my problem? I think not, but worth asking... i have never heard the humming before, when the car was running well.

One other thing about the humm... when i touch any portion of the metal parts of the motor with a mettalic object (such as a wrench or a flashlight), the pitch of the humm changes, like i am altering the electrical pulse/curcuit. Is this normal? It sounds almost like a computer processing data :) how wierd!

Loren: I found the first and second points you mentioned. - the one under the dash and the one on the back wall. However, the second picture (supposedly of the back wall one) shows one that is near the strut tower. I cannot locate this ground. There is a black film that is glued down around the tower, and I am nervous to pull it up. Is this where i should be looking? Also, I could not locate the plug near the passengers lower seat belt... is it beneath thte carpet? Or are you refering to one of the plugs in the drivers side, rear wall of luggage? Also, do you know relay assignments for the under-dash relays? Lastly, i learned somehting new about my prob. last night. When the Key is at Accessory, the motor itself (sounds like the throttle body) makes an electronic humming noise. This noise is present until the key is removed. however, when the CEL does not come on, the engine does not hum. What is causing the electronic sound, and how could it be related to my problem? Really truly Lastly, this motor is freakin dirty! It is perhaps the dirtiest motor i have ever seen. Is there any major grounds or distribution points in the engine comp. itself that i should clean/check? What about the maf? Has anyone ever heard of the MAF or any other sensor causeing a no-start, to include no CEL at Accessory? Honestly, does anyone know where the CEL at accessory comes from? Like, what system, via what switches/wires? I am thinking that maybe if I start at the source of the CEL and make my way back, I may find my problem. For example... if the DME decides not to start the car, how does it do it? Start inhibit? or is there another system? Wouldnt the start inhibit merely cut the spark? The fuel pump should still kick in, and the CEL should still come on. The problem has to be in a loose wire/bad ground. I have spoken with quite a few Porsche mechs... Dean McCrarys, EuroCars of Tallahassee, Gossett in Memphis, and even the Porsche Regional Service Manager for my area... after it ran for a few days, they all said that it is probably not a computer failure, since it runs fine sometimes. Every example i have seen of DME or Tip failure has resulted in a constant issue, not one that goes away for days at a time. The DME is covered under the emissions warranty... but if it is not the DME, then I end up paying dealership labor and such, plus have paid for towing across the freakin state of florida... which i am not willing to do yet. Does anyone in the Florida Panhandle have a PST2???????? I will BBQ and buy the beer! Brian

Car starts so intermittantly, its not even funny. It was starting fine today, but I replaced the switch anyhow. Took it for a drive, and sure enough, after about 15 min. of driving, it just died while on the road. Trans. went to safe mode, and when I tried to restart, no dice. Questions... This problem started immediately after I washed and filled up the car a few weeks ago. After a few days, and perhaps a quarter tank of gas, it stopped all-together and was driving normally every day. Then, when I got the car down near empty, it started again. It happens while rolling and while in park, going to safe and dying at the same time. It never goes to safe and stays running, it always dies, so I know the problem is inter-related. Also, when it goes to safe (flashing between the d and 4) the CEL is not on like it should be. Then, when I roll to a stop, the CEL obviously wont come back on. I dont do anything to get it to start again. Just leave it alone for a while (almost like it is cooling down), then the CEL comes on at ignition, it starts, drives fine until the temp gets up around 190ish, then dies again and wont restart for a while. Could my problem be related to temperature..., i.e. computer getting hot and shutting down? What about water... where are the grounds related to this whole system? I checked the #8 and #9 grounds today (the ones on the back wall of the rear compartment) and they seemed fine. Does anyone have a full relay assignment listing for the relay panel under the dash? I only have a partial one on my "alldata" subscription... There are quite a few relays that are not listed, and I would like to know what they all go to. Lastly, there is supposedly a large distribution center for all the electronics somewhere in the front passenger side of the car. Has anyone ever accessed this, and is there the possibility of water or something in there? I only ask because the starting problem began after I washed it. Is there any special way to disconnect the battery? Should I do it w/ accessory on? Then turn off the key? What about buying an aftermarket or used DME? Are they available out there? Sorry for all the questions.... :(

I have replaced the ignition switch. Was really easy. Thanks for the great instructions, Loren. Problem is, however, that the ignition switch was not the problem! I took it out for a spin, and sure enough, after about 15 minutes of driving, it went to safe tranny mode while in 3rd gear, and the engine died. No CEL when I tried to re-start, so it is currently sitting about 3 blocks from my house. I am gonna start a new post to clear up what is happening. Perhaps someone will have another idea!

Ok... so grounds points 8 and 9 right? Switch will be replaced on wednesday, and the batt is good. I am gonna check the grounds, check the Tip... ect. Question: Not too long ago you gave me some instructions on checking the canbus failure. Do the portions that involve the ECM being disconnected have to be done ignition on? Cause wouldnt this cause a fault in itself? Or are the checks (between pins 85 and 86) done with the key off?

Ok... so I went out and bought a digital Ohm Meter. Want to trouble shoot this canbus thingy... what is the Porsche special tool 9616, and is there a home remedy for one if you dont have one?

Ok... so it is getting really frusterating. Car started again last night, drove it about a block, and the CAN Bus fault happened again. When I stopped the car, the CEL would not come back, and the car would not start. Bout 20 mike later, it fired, kept the CEL on (due to the CANBus), and drove home. Fired this morning no problem, drove it quite a bit, then came home. when I left the house again, at the same location, the can bus fault happened again one block from the house... i mean, the same identical spot. Coasted to a stop, and tryed to restart... no CEL, no start. Its been a few hours now. Someone in the PPBB forum had the same problem i am having with the CEL and the no start. They never posted how they got it resolved though. I am so completely lost. Could a bad ignition switch (which is what i keep hearing from some locals recently) cause a canbus fail, and a no CEL at Accessory?. Not to mention, could a bad ignition switch cause a car to die while rolling? I suppose it could, but does this sound familiar to anyone? Someone tell Loren to sneak back and fix it again! :) Brian

The problem disappeared for a few days, put over 150 miles on the car! Could not stay out of it. Now it is back. Went out to the garage to go to the store, and turned the key... no CEL :( Hasnt started in about 1 hr. now. I noticed something else... when it does not start, I hear a few clicks from the back of the car. Today, I finally had my wife turn the key to accessory so I could locate the source of the clicks. It sounds like it is either coming from the DME Relay (slot 1) or the Start Inhibit Relay (slot 7). I swapped the DME Relay with my engine fan, no dice. I dont have a relay that matches the Start Inhibit Relay, so I cannot see if there is a fault in it. Is it normal to have a relay click like that (so loud that you can here it with the trunk shut), and is there any relay I can swap with this one to see if it is the problem? Not thinking ignition but replacing anyhow... on my way to Auto Zone to order it... Thanks for the help...

Ok... some of you may have seen the problems that I have been having with my box. The constant posts and questions, the confusion. I have to share something with you. I believe that Loren, fed up with my constant questions, snuck into my garage last night and fixed my Porsche. It runs fine... put 60 miles on it today, stop and go, multiple starts, etc. No safe mode tranny, no ignition problem. Honestly, after all the work i have done tracing out wires, checking relays, and $$$ to a useless shop, the car just fixed itself. Now, I havent put it in TIP mode, been driving in auto. And I know there are still issues here... but all it took to start it was sitting there, wiggling the key around while bored last night. After a few minutes of wiggling (I had previously went to every relay and re-checked), the CEL came on and it fired. Fired every time since (currently knocking on wood). Thanks to all of you for your help, and I will keep you all in the loop the next few days. Also, I am sure I will encounter new problems to ask about... but on the bright side, I wont have to keep stealing my wifes Jag. Brian