2000 996 Won't Start

[Lakeview3]

Hello Friends,

I have not posted here before but have done some lurking. I have posted this on the other forum and not solved my problem. I know people here look at multiples like I do but hopefully someone different may solve my problem.
I have several 996's that I am currently working on. The one in question is a 2000 Cabriolet C2. I bought the car with the engine removed/tore down after a trip to Motor Meister.
I purchased a salvage 1999 996 C2. Car would run and drive when I got it. I had a shop remove the 99 engine. All the e-gas components were changed onto the 99 engine including wiring harness, intake, throttle body, etc.
After they installed the engine they could not get it to run. They said the fuel pump was bad. At that time I picked up the car. Since that time I have spent hours trying to troubleshoot the problem.
The short version is....... I have jumped the fuel pump relay and pump will run. Car cranks normally. I do have fuel at the rail due to an observed fuel leak at fitting.
My OTC scanner will not show the engine to have rpm while cranking. Changed the crank sensor with known good one from my parts car. Performed all the relay checks per the Bentley manual. FIO relay test checks ok. The kicker is at the DME relay.....Check continuity to ground at terminal 85. This is done with switch on. I have no ground with switch on. I have ground with switch off.......
I have checked and cleaned all of the grounds. The manual states, If ground is not present, signal from ECM is missing. Check wire between control module and relay.

My main question is which wire is it in the ECM??? Can I check continuity from ECM to relay ground wire to solve the problem?

I am not strong in wiring diagram reading and the manual seems confusing. I have undone and checked for corrosion and wiggled with the switch on all the ECM wiring, no change. I fear I have a pinched/broken wire in a harness. I checked the plug going to the crank sensor with the switch on. One wire had 12 volts, one had 5 volts and the other had ground.
The car did have a leaking top. It sat outside for a while before I realized this. As far as I could tell it was only on the passenger side. Another question.....Would the immobilizer under the driver seat play a role in the no signal to the ECM? Even though the car will crank should I take the seat out and check for corrosion?


Sorry to get so long winded, but I don't have much hair left and my patience is very thin. Hopefully someone more knowledgeable than me can point me in the right direction......

Thanks in advance

[Lakeview3]

No ideas from anyone out there in cyber Porsche land? Just looking for a little direction/suggestions on which way to turn.........

[S ECU Repair]

It wouldn't be a strech to consider that the Immobilizer got water damaged since you mentioned that the car had a leak at one point.

This will definitely cause a no start issue.

Check the circuit board for corrosion and if you see some, that will answer your question.

Let me know.

[Lakeview3]

Originally Posted by S ECU Repair

It wouldn't be a strech to consider that the Immobilizer got water damaged since you mentioned that the car had a leak at one point.

This will definitely cause a no start issue.

Check the circuit board for corrosion and if you see some, that will answer your question.

Let me know.

Thanks for the response.
The answer is yes, I have removed the drivers seat and module. Removed board from its housing and it looks perfect. No sign of anything. I have also checked all the connections and pins on the DME.
I am trying to get my hands on a Durametric or buy a PIWIS system since I will be doing a fair amount of work on these cars.
Once in say 30 key to on the fuel pump will come on and run for about 2 seconds and stop. This is what is making me think it is a wiring issue........

[S ECU Repair]

Definitely test your car's ignition switch. Many mechanics replace both parts of the swicth (electronic and mechanical) because the original ones tend to fail and give you intermittent behaviors.

[Lakeview3]

Originally Posted by S ECU Repair

Definitely test your car's ignition switch. Many mechanics replace both parts of the swicth (electronic and mechanical) because the original ones tend to fail and give you intermittent behaviors.

First, Thanks for the response!

While checking relays and grounds under the dash, I did notice that I pulled the harness off the switch rather easily by accident.
Other than at the switch harness where else would I check?

Does the key transpond with a module like on some other makes?

Low battery in the fob matter???

Just guessing here..........

[BYprodriver]

Originally Posted by Lakeview3

Thanks for the response.
The answer is yes, I have removed the drivers seat and module. Removed board from its housing and it looks perfect. No sign of anything. I have also checked all the connections and pins on the DME.
I am trying to get my hands on a Durametric or buy a PIWIS system since I will be doing a fair amount of work on these cars.
Once in say 30 key to on the fuel pump will come on and run for about 2 seconds and stop. This is what is making me think it is a wiring issue........

I have a PST 2 laptop version I will sell for $2,000. This is what Porsche dealers used when the 996 was new. Porsche will not sell a PIWIS system but you can rent it for $15,K.

[Lakeview3]

Originally Posted by S ECU Repair

Definitely test your car's ignition switch. Many mechanics replace both parts of the swicth (electronic and mechanical) because the original ones tend to fail and give you intermittent behaviors.

Well, I changed the electronic part of the switch. No change. I borrowed a Durametric reader and it shows a code P0336 Engine speed sensor open circuit. I have changed the crank sensor with two from known running cars.
Using the Bentley manuals wiring diagram the pins it shows in the round wiring harness with the gray plug are wrong. I have a core engine, same year
with the harness intact and the wires are completely different.
I think I have a wiring problem, but just don't know where. I do have a PIWIS system coming and hopefully it will be more in depth than the Durametric....