Cavalier traction control

First course of action will be to ascertain what trouble codes are present in the fault memory of the TC ECU. This can be done by a garage with a fault code reader, or you can do it yourself by linking the TC diagnostic pin to earth at the ALDL connector under the bonnet. The procedure on how to do this is explained on several websites, a quick google search should find one. Once you have linked the correct pins, the TC light will start to flash - the sequence of the flashes tell you the fault codes stored.

From your description of the fault, I would guess that there may be a wiring fault between the ABS and TC ECU's. The signal from the wheel speed sensors is shared between the two ECU's. If a sensor was faulty, then the ABS lamp would light as you pulled away. As you are only getting the TC light, then I would suggest the ABS side of the system is OK. Obviously, only further diagnostic testing can ascertin the exact cause of the problem.

HTH

Anthony Remove eight from email to reply.

Thanks. I've found a site about reading the fault codes and I'll give it a try - probably at the weekend.

Cheers,

Iain

Hi again,

I found the ALDL connector and shorted the 2 pins. From the flashing lamp on the dash I read fault code 31. (The flashing sequence was a repeating 1-2,

1-2, 1-2, 3-1, 3-1, 3-1 pattern).

The instructions that I downloaded would appear to indicate a faulty (or disconnected) engine RPM signal (crankshaft sensor).

Does this sound sensible? Is the RPM sensor _only_ used by the traction control?

If so, does anyone know where it is located? My Haynes doesn't cover the V6 engine :-(

Thanks,

Iain

The engine RPM signal for the TC is obtained from the engine ECU. The signal at the ECU comes from the crankshaft position sensor. This sensor is located in the engine block, behind the PAS pump bracket. If you had a faulty crank sensor, the engine management light would illuminate. As you do not have an EM light on, there are three possibilities (in order of likelihood):-

1). Wiring fault between engine ECU (behind drivers side kick panel - where the bonnet release is) and TC ECU (located behind water shield on bulkhead, near brake servo). 2). Faulty TC ECU 3). Faulty Engine ECU.

You would need to check for a pulse at pin 6 (green wire) on the TC ECU. This feed also drives the tachometer. The easier way to diagnose this would be to use a Vauxhall TECH1 tester to monitor the data parameters, which would show if an RPM signal was being received.

If you need more help, let me know.

HTH

Anthony Remove eight from email to reply.

Hi,

Thanks again for your advice.

I was puzzled by the EM light not coming on, but I'm equally puzzled why it's reporting an RPM sensor failure. (ie Why no warning light when it's aware of a fault?).

Is there a wiring diagram anywhere that would show these connections, so I could understand what's wired where? Is the diag at the back of the Haynes going to show what I'm looking for?

The tacho's working fine, so I guess there may be a dodgy connection at the TC ECU. I'll have a look when I can, but it's starting to look like a garage-job.

Thanks again,

Iain

The RPM signal is making it to the engine ECU, but is not being recognised by/sent to the TC ECU.

There is a diagram at the back of the Haynes manual that is relevant. Even though the manual does not cover the V6 engine, the wiring diagram for it is included.

HTH

Anthony Remove eight from email to reply.

Thanks - I'll have a look and see if I can sort it out.

Failing that, I took out some insurance a while ago for parts...might be time to see if that's worth it's montly payment!

Cheers,

Iain

The RPM signal may be due to the fact you ran the diagnostics without the engine running, try the diagnostics again with the engine running.

It was running, but I'll test it again to be sure.

Cheers,

Iain

connections, so

Hi again,

Can you give me a bit more advice on where the TC ECU is? I had a look yesterday but it was cold/windy/snowing/getting dark/generally horrible so I didn't stay out that long.

The nearest thing I can find to what you described is a long, thing rectangle-section black plastic duct that runs behind the fuel injection manifold, and does a 90-degree turn towards the front of the car, where there's a connector thing. The wires then disappear under the plastic cover on top of the engine.

Am I getting close???

Cheers,

Iain