I have a '03 jetta tdi. the engine light is on and code reads #3 glowplug. It is fine, as are the rest of the glow plugs. I reset the code and it returns within a day or so. my daytime running lights also don't work. someone told me that they might be on the same relay? could that be true? Or are these independant problems? my backup lights also stopped working. All 3 of these things happened (or were noticed within a week of each other) could they be connected? any troubleshooting hints would be greatly appreciated.
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You can get a wiring diagram free at Autozone.com for most cars. You need to register on the site free and then scroll to the bottom of the Web page.
There may be a reference to how the Glowplugs are wired and it is possible that they are wired as pairs from the Timer box. This would mean that 1/2 the Timer box is shorted out or that a Relay that controls just that pair of glowplugs is a bad Relay. If there are 2 Relays for the Glowplugs, just swap them and see if the problem moves to a new pair of cylinders. This would confirm a bad Relay.
You may also have a bad ground. Look to see the wiring for the ground circuit. This would be a good bet if each pair is separately grounded. You could also have a problem with not replacing all 4 as a set. I do not know what VW recommends for this.
Perhaps you should test the Glowplugs. You test them by fixing a battery jumper clamp to the bottom of the casing of the Glowplug avoiding the threads. Then briefly touch the top of the Glowplug with the power cable of the Plus charge. Be careful not to melt the part.
The Glowplug should glow equally between the set. They should not stay dark. And remember, the Timer only has seconds to work. That is all the time the Glowplugs have to vaporize the fuel.
The glow plugs work in direct relation to the engine block temp. The relay for the glow plugs is obviously reading the wrong temp, that's why they turn back off. It's most likely that the temp sensor is bad, but trace the wires back and make sure there are no breaks in the insulation and they are well connected at the plug-ins. I have seen a lot of wires at the connector look good but fall off as soon as you touch them.
If the temp sensor is the same on for your your dash, then borrow a heat sensing gun and double check it against the guage. I have seen them read wrong by as much as up to 20 degrees. If the sensor reads rught and feeds both the guage and the glow plugs, then the problem would be either the wire harness or the glow plug relay. Hope this helps.
There is a big fuse in the engine room for the glowplugs.
You'll find it just near the brake vacuum cilinder under a black cap...
Hear if the glow relay ticks when you'll put power on. Does the glow light lights on?
It's a relay, not a sensor. It could also be the harness - although I don't believe a harness problem would cause all four plugs to show bad. Here's everything you ever wanted to know about glow plugs: (with photos). Check out the rest of the site too - these guys def know their TDI"s...
Take off the glow plug power bar and check each glow plug with an ohm meter. Infinite resistance means it's burnt out. Check the three glow plugs on the right side of the head with your ohm meter as well.
Just removing and reinstalling the bar will fix any bad connections which might also have triggered the errorcode, so when none of the plugs seem broken, that might have been the case.
I had the same faultcode on my 2005 TDI some years ago; it ran perfectly, but after checking under the hood 1 of the plugs was indeed broken.
1.) Don't do anything. Once the computer sees the engine run normally for a few cycles, it will automatically clear the code.
2.) Connect a scan tool to the OBDI port to clear the codes manually. Local auto parts stores will often perform scan tool diagnostics free of charge.
3.) If you want to remove the code quickly without any special tools, just disconnect the battery and leave it disconnected for a while. (How long varies for different cars, as some engine PCM's have capacitors that hold a charge for a short while after losing battery power.)