Glow Plug Light Effects Auto Gearchange

[Mel]

Hello, 2003 TDI with auto box. The glow plug light has just begun to stay on for over three minutes when first turning on. The car starts perfectly with the light on but seems to change gear without the clutch! Very hard and clumsy. If I wait for the light to go out before starting the gearchange is fine. Occasionally the light goes out as normal. about two seconds. Otherwise the car appears to be normal

Any idea where to start looking

[big_kev]

On the MK1 the glow plug light doubles as the ECU warning light........basically if there is a problem with the ECU the engine runs like a bag of spanners and this will affect the Auto Box......I am assuming the MK2 is the same.

 

The ECU is unlikely to be the source of the problem....they are pretty indestructible...more likely it is a problem with an associated circuit...relay...MAF...or brake switch.

 

The intermittant problem would most likely point to an electro-mechanical fault and therefore I would be looking at a Relay or switch.

[Mel]

Thanks for that, I'll start pulling it to pieces this afternoon and keep you posted. I suspected that it might be an electrical fault upsetting the ECU but didn't know where to start.

 

Mel

[Scorpiorefugee]

I'm with Kev on this. He's absolutely right. In my experience I've always found that it's best to forget the side issues like gears and warning lamps and look for something else.

 

Logically, it could be something that is only important in the warming up phase but it would probably help if you could get the error codes reset and then read again during/after warm up.

[Mel]

OK, thanks for the advice. It looks like you are correct as it appears to be the coolent temperature sensor, wiring or plug at fault because if it's disconnected the problem is solved. Makes sense I suppose as the plugs stay on thinking the engine is cold. This could also explain the gearchange as the engine would probably be running very rich at high idle as well. I just need to identify if it's a poor connection or whether it is the sensor itself.

Thanks again for your help.

 

Mel