C4Spolar

Hello.

I have a 1996 993 turbo previuosly with a DME Immobilizer bypassed. I installed a newer 1998 DME with immobilizer and the car won't start. Here is a list of what I checked in the car so far.

!) My Immobilizer unlock doors with FOB, activate the DME and I'm able to crank the engine, so the Immobilizer works as it should.
2) DME relay work, fuel pump work and I have fuel pressure up to the fuel rails.
3) Install the 98 DME with Immobilizer in another 993 and everything works in the other 993.
4) Installed a new crank sensor.
5) Install a NOD light in fuel injector connector and no pulse. so NO FUEL
6) Install an inductive timing on cylinders #1spark wire and no signal, so NO SPARK.
7) Waiting for a new head temp sensor replacement.
8) Driver airbag delete.
9) Install a Durametric test but only reads the DME type and serial # since I can't fire the engine. So Durametric doesn't help me.

It seems something is stopping the DME unlocking the full start sequence to fire up the engine, what bothers me is when I install the previous DME with Immobilizer bypassed and everything works. I'm running out of ideas.

Any thoughts would be appreciated. Thanks.

pp000830

Hi C4Spoler,
Did you test the fuel pump when powered by the DME relay or just jumperd it to make it run? I it runs being jumpered but not when attached to the DME Relay the below may help.
The DME relay has two relays in it one wakes up the Motronic ECU. Possibly the internal relay used to do this is faulty.
DME relays can be dead or intermittant as new out-of-the-box.
Pry it open and inspect it or just get a new one:
In the 964 and 993, the DME-ECU has a permanent 12-volt feed that maintains it in standby mode to preserve its internal memory, fault codes, Readiness flags & adaption data. When the ignition is switched on the DME-ECU sends a current to the DME Relay which then switches the DME-ECU from standby to ready mode to control the engine. Then when the starter motor is cranked, the DME-ECU activates the second relay in the DME Relay housing that powers the fuel pump for as long as the engine is running.
Andy

systemsc

This indicates that '98 DME ECM with the active immobilizer system is not receiving the unlock signal from the immobilizer, even though the immobilizer can lock/unlock the vehicle.
Don't waste your time & money buying parts, e.g. temp sensor, since you know it runs with the bypassed immobilizer DME ECM.

C4Spolar

Hi Andy.

Nothing is jumped at the DME relay area. I have a F9T solid state relay with the 4 LEDs indicator and the fuel system works like it should and lots of fuel up to the fuel rails.

Something in my car doesn't let the DME to trigger the injectors and coil and fire up the engine. The DME (ECU) and Immobilizer was tested in another 993 and it works. So those 2 elements are eliminated in my problems

systemsc

So you tested YOUR immobilizer in the other vehicle with the '98 DME ECM? The key point here is; The engine starts with the bypassed DME ECM, so all the DME ECM inputs are OK!
The problem then is a wiring problem from the immobilizer to the DME ECM, i.e. the immobilizer start command is not getting to DME ECM.

C4Spolar

Hi Loren.

My Immobilizer gives me pressured fuel up to the fuel rails, let me crank the engine and when the key is ON my idle bypass valve vibrates. I tried my DME in a 1997 993 C2S and it works, something in my car doesn't let the DME to activate the injectors and coil. I checked my alarms connections and airbag terminal and everything seems to be in order.

I really don't want to do an Immobilizer bypass on the 98 DME. It's got to be something stupid.

C4Spolar

OK I will check the wiring between the DME and Immobilizer.

Thanks Loren.

systemsc

You tried the '98 DME ECM AND your immobilizer in the other vehicle?

C4Spolar

PS: I havent test my Immobilizer in the other car, just the DME, my understading of the Immobilizer it let me open my doors, wakes up the DME to do it's job.

systemsc

You're correct, but they're two independent functions.

systemsc

A quick test to determine whether the DME ECM (W-line) & the immobilizer (K-line of OBDII connector) get connected, when the remote is activated, is to use a generic scanner and read the actual values of DME ECM.

jay@EZimmoblock.com

That's the odd thing...the Durametric is able to read DME type and serial number, so there's connectivity from the OBD port, through the immo, to the ECU.
Is it possible the reason the immo bypass was done on the 97 ECU was because the same problem?

C4Spolar

Hi Jay.

My previous DME was OK, I just wanted a bypass because I was annoyed with the FOB clicking. When I sent my previous DME for the bypass to ECU specialized in 2021 I sent also my Immobilizer with it to have new FOB's sync and they may have tempered with my Immobilizer.

jay@EZimmoblock.com

OK, good. Your immo was working at one time (with the original ECU). The immo is disarming ok and it has connection to the ECU. Why it won't give start permission is a puzzle. A good test would be to see if YOUR immo works in the other car preferably with the 98 ECU.

systemsc

This also occurs when using the Porsche PIWIS tester and when the DME ECM has been modified. This typically doesn't occur when using a generic OBDII tester and reading actual values.
As mentioned up-thread, consider using a generic scanner to provide more info on your problem. You might also consider again testing the '98 DME ECM on the other
vehicle where it ran the engine, and using the Durametric, and whether the immobilizer has been bypassed on the '98 DME ECM, or some other modification. You can jumper the starter
relay (30 to 87) and not use the immobilizer (no remote) on the other vehicle to test whether a bypass modification was done to it too, when starting.

Hopefully, both vehicles are turbos, and your '98 DME ECM is for a turbo.

Note: I seen where some 993 turbo ECMs being sold have been likely modified, i.e. the DME ECM has been opened. Has your '98 DME ECM been opened?
Also, a '98 DME in a '96 will develop an EVAP fault code, i.e. the emission system in the '98 DME ECM was changed.