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chris, Expert VW technician
Category: VW
Satisfied Customers: 704
Experience:  Almost 10 years experiance, top technician western region, Team leader
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2001 Jetta TDI: split second..the glow plugs to not stay on

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Help! On my 2001 Jetta TDI my glow plug indicator lamp only comes on for a split second. On extreamly cold days it is extreamly difficult to get the car to start. What would cause the glow plugs to not stay on long enough?
The glow plug circuit consists of the plugs the relay and a harness. If the plugs are ok there might be a problem with the harness. I have replaced several harnesses for glow plug faults. Before replacing any parts I would check the ecm for any faults. The harness that I am talking about is the one that goes onto the glow plugs.
Customer: replied 7 years ago.

First of all thank you for replying.

I did check over the portion of the harness leading to the glow plugs and I don't find a problem. I don't have a check engine light on and my glow plug lamp doesn't flash (like some other posts describe). So if I'm understanding correctly the ECM commands the glow plug relay to power up. I'm assuming that the dash indicator lamp would indicate the actuial glow plug on period. In my case the glow plug lamp goes out once the bulb check cycle ends. Would you still suspect are harness problem or something else?


I don't mean to be a pain the the rear, I'm a ag electronic specialist for Deere equipment. I work with electrical problems on Deere equipment for a living. Right about now I'm wishing I had a wiring diagram for this little car. :-)




Send me your VIN and what you want to check I can look up some diagrams and send you some ideas. I can't send you the actual diagrams due to copyright laws but I can point you in the right direction if it helps.
Customer: replied 7 years ago.



Ok, I would like to know what pins on the glow plug relay should have power, or ground when the glow plugs should be on. I need to verify that I am getting the signal from the ECM to the relay. Well in short can you tell me what pins on the relay are used and what their respective job is. Like any relay this one has all the pins numbered. I think if I can determin which pins should have power and ground I can at least figure out if the relay is doing its job.


Thank you for taking the time to help me out.




Main power supply for relay is the second fuse from your right on the fuse panel on top of the battery to pin number 2 on relay panel


Pins 4 and 6 go to the glow plugs


Pin 3 is ground should be brown all grounds on VW's are brown


Pin 7 goes to pin number 33 on ecm and it should be green at the ecm


pin 1 goes to pin number 42 on the ecm and is lilac with a white tracer


Pin 9 gets power from fuse box on the left side of the dash

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