Well, all my sources of info caution against just anybody trying to dig into this stuff...

I just got through with a full rebuild on my 996. The IMS bearing and shaft self destructed causing the rebuild. After getting it all back together, I started the engine and ran it for 20 minutes. Several stops and starts later I backed it out of the garage revved it a few times to 3000 rpm and the CEL came on and the engine shutdown. Now it will turn over but will not start. Here are the facts:

It is a Tip so no clutch switch
Engine turns over will not fire
Battery is fully charged
The fuel pump does NOT prime when the switch is turned on
The fuel pump and relay are both good
I used a clone PIWIS and no DME codes are present
I can read the information from the DME
The Air Bag light blinks then stays on when the key is inserted and turned to ON
When I read codes from the Airbag I get "Current Fault Codes 0 module failed to initialize"

Any ideas are appreciated.

*Should such a thing exist.

Minus 40 degrees... Is that Fahrenheit or Celsius?

I assume that you are talking about the crankshaft sensor at the flywheel. If that were it, it would show a CEL error code in the DME. I do not have any DME errors. The one that conrcerns me is "Current Fault Codes 0 module failed to initialize".

When my crankshaft position sensor was failing, there were no CEL codes thrown. Unlike your situation, the non-starting was sporadic, only after the engine was hot. It would crank but not start, once it cooled down, it would start fine.

Minus 40 degrees... Is that Fahrenheit or Celsius?

Ah, brain cramp. Inertia sensor. But if it were that, I would see a code in the AB module. To me it appears that the AB module is not talking to the DME.

That the engine cranks tells me the car's security system is working and recognizes the key's RFID.

The engine lacks fuel, spark, or the engine controller refuses to trigger either because some critical engine sensor is malfuctioning or sending implausible information. The crankshaft position sensor is one such sensor.

The failure of a critical sensor at startup is not likely to trigger a check engine light since emissions are not affected. A real PST2 or PIWIS might be able to detect/report the failing sensor but I have my doubts about the PIWIS clone.

Be sure the crankshaft position sensor is hooked up properly and bolted properly in place. Sometimes this gets bolted up incorrectly or bumped out of position during engine/transmission installation and if so it will not work properly.

Sincerely,

MarcW.

Yep. And verified that the relay is good also. I have verified that the crank sensor is ok. Any idea wwhat "Current Fault Codes 0 module failed to initialize" means on the AB module?

(safety restraint system) it appears there is something interfering with the critical communication that must take place as the AB/SRS controller runs through its system checkout which it does whenever the key is turned to on.

The AB/SRS light should go out almost immedately after the key is turned on but the actual checkout takes a few seconds longer. If a problem is found during this checkout the warning light is turned on.

If the light comes on immediately, and stays on, flashes even, that suggests a hard failure of the AB/SRS wiring/communication link. Under this situation the AB/SRS may (may) prevent the engine controller from allowing the engine to start. It will crank, cause that's a pretty simple/basic circuit and it needs no more complexity than it already has. But the engine controller still has the last word as to whether it will allow the engine to run.

Beyond the above... I don't know.

Sincerely,

MarcW.

What you describe is a very close match to what I am seeing. Is there any material that tells me how to troubleshoot the system other than the Porsche manuals? I have them and they are pretty remedial. Mostly continuity testing. They also call for a special tool Part number 9516 and 9516/1. I assume they are a load device that allows testing without putting a voltage across the actual airbag which would be very exciting if only for a second.

Quote
rkellison
What you describe is a very close match to what I am seeing. Is there any material that tells me how to troubleshoot the system other than the Porsche manuals? I have them and they are pretty remedial. Mostly continuity testing. They also call for a special tool Part number 9516 and 9516/1. I assume they are a load device that allows testing without putting a voltage across the actual airbag which would be very exciting if only for a second.

Proper training, test equipment, and so on is crtical to avoid serious injury.

I can give you some general things though...

The airbag system is constantly checked by a diagnosis unit in the triggering unit. Any fault is signaled by the warning light. The light lights up approx. 3 seconds after ignition is switched on and goes out if not fault has been entered into fault memory.

If the light lights up again this indicates a fault in the system and the fault can be read with the PST2.

A period of 10 seconds is required to enable the triggering unit to id all faults in the system.

In order to guarantee every possible fault source is found the ignition must be switched on for at least 10 seconds.

You really need to be able to read the fault number.

I find no fault code 0 in my references.

Fault codes 1 and 2...

Ignition on. (Due to a short circuit bridge in the plug of the triggering unit for the air bag the warning light wiring short-circuits to ground if the plug is disconnected.)

Possible causes of faults: Faulty fuse. Airbag wanring light faulty (no bulb, can not be exchanged).. Short circuit to B+/ground or open circuit in the wiring between instrument cluster and the airbag triggering unit.

Fault code 3.

Supply voltage.

Ignition on.

Possible causes of the fault: Low battery positive voltage. Check battery or alternator. Check ground points and the plug connection on the airbag triggering unit for corrosion.

And so on through the rest of the fault codes.

You really need to know the fault code(s).

Sincerely,

MarcW.

That is the unit under the Driver seat, correct? If so, I have and it is good.

Edited 1 time(s). Last edit at 06/05/2011 09:26PM by Boxsterra. (view changes)

OK, I have part of the mystery solved or at least narrowed down. It appears that the problem lies in the AirBag module. If I put a meter on the "Crash" output of the AB module I can see it start out at 12V as it goes through the self check. When it completes it, the voltage drops to 2.5v and the AB light comes on. If I open that circuit up(cut the wire) and apply a 12v signal to it, the engine cranks and runs OK. It is as if the AB module thiks that the car had been in a crash and has disabled the fuel flow. The question now is what portion of the AB circuitry has a problem and is telling it that a crash has occurred. From looking at the schematic, the parts monitored are seat belt buckles, child switch, driver airbag, passenger air bag and both side air bags. I know that the buckles and child switch will not cause a crash signal. I need to know how to test the air bags themselves. I assume that they have a resistance measurement and that once they are deployed that resistance is no longer there. If I put a Ohm meter across the airbag, will it deploy? Anyone out there an "expert" on SRS Airbags?

deployed. The engine died but I was not sure if I killed it/stalled the engine at the time of the impact, of if the collision caused the fuel pump to shut off.

A week or so later after the car had been declared a total loss the car needed to be moved around at the body shop where I had taken it. The helper got in and started the engine right up. Airbags handing down and all. I asked him what he had done to resurrect the fuel pump and he said 'nothing'.

Sincerely,

MarcW.

They can read the code which will tell you the source of the airbag fault.

The various faults are for: ignition circuit, airbag warning light, supply voltage, selt belt tensioners, side airbags, belt buckles, child seat detection, side airbag sensors, airbag triggering unit.

The first place to start is where any recent work has been done in the area of any of those components. It could be a bad ground (check pins 2, 4, 17, 19 on the airbag triggering unit plug) or a loose plug. This is assuming there is no moisture under your driver's seat.

It is much more likely to be a wiring problem than an actual airbag unit problem.

Thanks. I had the entire steering wheel apart and will start there. I also had the passenger AB out and the entire dash out. Funny thing is that the engine ran fine for an hour or so. I am going to pull the drivers side AB and replace it with a 3.9 Ohm resistor then check it form the connector on the AB Module. That will tell me if the clockspring is OK.