alver

After changing the fuel pump on my 1990 C2 Tiptronic, my car is now stuck on limp mode (3rd gear) I might have damaged some control unit after jumping the fuel pump relay several time!
(!) The tiptronic warning lamp does not light on the clock when the ignition is switched on. My Durametric cannot communicate with the Tiptronic Control Module/Unit = "signal unplausible" I guess.

The Porsche Diagnosis Tiptronic manual recommends two test points:

"Test point 1" it says in case of a "signal unplausible (Fault code 11)" to test the voltage control unit,

1) Tiptronic warning lamp does not even light on the clock when the ignition is switched on

• check fuse (Central Electrical System) - measure voltage at fuse ----> no voltage, check wiring to DME relay or operation of DME relay, respectively. Measure voltage at ECU connector pin 1 ----> no voltage, check wiring according to wiring diagram

2) Voltage outside of valid range
Test point 2
No diagnosis possible. Open circuit, short to ground, loose connection.
Check fuse (CES). Fuse faulty:Pull off connector at ECU and Check pin 39 for short to ground. If no short to ground: ECU faulty. If fuse ok, check voltage according to wiring diagram.

Which fuse number? I tested all fuses since I do not know which one the manual referred to.

I followed that testing protocol (battery, alternator, relay, relay terminal all good, 12.5 volt at terminal 39 so it looks like I got a faulty transmission control unit.

Before I buy a used transmission control unit, I was wondering if anyone else encountered the same situation and was able to fix the limp mode? Also, does anybody know of a company that can rebuild an electronic TCU in the US?

Thanks,
alain

alver

Ok, here it is: Tiptronic wire was defective going to the TCU. All is good and now my Porsche Durametric Diagnostic Tool can access the Tiptronic control unit. As far as the fuel pump I just had to replace the battery!