Dazzler 911

Issues:
Only starts on ignition key release.
Tiptronic does not change gear (in 3rd)
gauges flicker

changed:
Battery ground lead
ignition switch
Starter motor
battery

Garage reported ABS wiring hot?
Im suspecting an earthing issue.

Any ideas ?

justin-in-athens

Is ABS functioning properly? You should get a warning light in the clock if not, but the bulb could be out.

Car is stuck in 3rd gear all the time? I have seen a weak battery cause this.
There is a fuse for the tiptronic control unit #8 I believe, but that is probably not your problem.

Can you manually change the gears with the selector?

It does sound like a grounding issue. Car starts ok?

Dazzler 911

ABS works all OK, although there is a bleeping noise when cranking the car over (the only reference to this I can find online is to do with the brake pressure warning.)

The car does start OK but only fires up once the key is released from the cranking position on the ignition.
The DME relay has been changed also.
Fuses seem to be ok whenI last checked but will check them again.
When the car starts moving the tiptronic warning light illuminates immediately and the car goes to third. It will not change manually either. The car does sit around for long periods and the battery is disconnected also as it was draining it quite quickly. The garage who changed the starter motor did not report anything wrong with the earth straps underneath but they might not have measured the resistance.
The car worked perfectly before the issues started.
Thanks for your help.
Darren

justin-in-athens

If you have access to a durametric or some other reader, you might check to see if there is a fault stored--i'm betting there is. You could try removing the small wire that attaches to the positive battery post to remove the ABS system from the equation. Have you tried disconnecting the battery for a while to clear the faults? The car defaults to 3rd gear as a kind of limp mode. The transmission control unit is located in the front boot down by the spare tire. You might unbolt it and give the connector a cleaning. If you have access to a spare, you might install it.

JohnK964

the control unit for my tiptronic is under the drivers seat MY91 C2

justin-in-athens

That is the Motronic engine management computer, otherwise called the DME or ECU.

The TCU is located in the front trunk down by the spare;

JohnK964

that pn in is the abs ecru the tip ecu is under the left hand seat I just removed it from my car MY91 C2 tip

justin-in-athens

You are correct! I was woefully mistaken. I've had it in my head that way for years.

JohnK964

Don't feel bad I recently thought my car had 2 fuel pumps

justin-in-athens

lol. I hope you are able to get this resolved without it being too costly. I don't think those control units are really prone to failure--but it could be that. I am not sure if a stuck microswitch in the console at the gear selector would cause this kind of behavior, but its something to look into.

JohnK964

JohnK964

In the picture above tip ecu is on the bottom main dme ecu is the top unit

JohnK964

From what I have read it is more likely the switches on the tip shifter

Dazzler 911

Thanks for all your replies.
I will check the selector switches but the fact that it cranks over but only starts when you release the key back to the ignition on position makes me think it may be an earth issue. Im hoping its something simple and it just a matter of finding it.
Thanks all for your input.

4th911

Interesting what you guys are talking about, I just collected my 1990 C2 Tip after several months of painful rebuilding work and while the Tiptronic shifted okay, I could not use the manual gear selector. Any idea what could be the problem?? There is no fault code...help!!

Also, the tail which was working fine until the day before I collected it, wouldn't automatically rise. I can raise it by using the tail switch, but then it would not go back done after I have used it. But if I let it sit for a day, I can bring the tail down using the switch. Strange gremlin this!

Any thoughts onthe matter is appreciated.