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Old June 22nd, 2006, 16:59   #1
dyvyd
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Default Check Engine light on @ 30 seconds after start, after all maint. done

Sorry . . . i'm new & read through FAQs, troubleshooting, &c., just not sure where to dive into an existing thread or add mine, though i found lots of info on check engine light problems. So . . . forgive me if there's a better place for this.
i have a '98 Jetta TDI w/137,000 miles; bought the car a couple years ago w/114k miles, all 4 engine glow plugs were replaced in Spring 04.
CEL comes on approx. 30 seconds after starting, no variation in cold or warm weather, no other symptoms at all, car runs fine, fuel economy is pretty consistent. My mechanic has a scanner & initially got error readings about glow plug monitoring & cooling system, i don't have the exact error info. He replaced the 3 cooling system glow plugs, reset the system and it was fine for about 2 weeks. Local dealer advised changing the glow plug relay. Did that, no change, CEL still comes on religiously.
Mechanic said there is also a relay for the cooling system glow plugs but the idiots at the local dealer could not even ID the part for him much less order. As in troubleshooting info in FAQs, he also checked resistance between glow plugs and block. About the only thing he didn't do is replace the glow plug harness. So . . .
1) am i better off just having him replace the harness & then try to reset the CEL? or,
2) Should we try to find this cooling system glow plug relay and replace it?
Basically my mechanic did everything the error readings prescribed and anything the mechanics at the dealer suggested that seemed to make sense.
Any other suggestions? Sorry for the long post . . .
dyvyd
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Old June 22nd, 2006, 17:30   #2
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Look at replacing the water temperature sensor as this tells the engine when and when not to use the glow plugs. under $5 from Tdi parts. less than 10 minutes to fit.
http://www.inmud.co.uk/page28.htm
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Old June 22nd, 2006, 17:46   #3
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I agree with aham_uk, put in a new coolant temp sensor. If that is not the problem I would think about the glow plug harness. I had a persistant CEL, changed the glow plugs and the temp sensor and when that didn't fix it the wiring harness did it. There is a how to somewhere on here with pictures.
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Old June 22nd, 2006, 18:09   #4
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HolySmoke?

Yeah, replace the harness.

I don't think the coolant GPs are monitored. And the don't come on unless your coolant temp is down around 0F. HOWEVER, the engine GPs come on every time (afterglow).
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Old June 23rd, 2006, 04:52   #5
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Quote:
Originally Posted by aham_uk
Look at replacing the water temperature sensor as this tells the engine when and when not to use the glow plugs. under $5 from Tdi parts. less than 10 minutes to fit.
http://www.inmud.co.uk/page28.htm
It may not even need replacement. In my case removing the replacing the plug took care of it.

Additional note: I used the same plug, but just unplugged it and pushed it back on, cleaning the contacts in the process. I realize the above sounds like it put a new plug on, which I did not.
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Old June 23rd, 2006, 09:17   #6
frerk
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I cleaned my harness with DeOxit from Radio Shack and haven't had a CEL since. Before that it was a plague. I suggest giving that a try first, its cheaper.
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Old June 23rd, 2006, 12:53   #7
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My wife's Jetta SW has the same problem and we just had the TB changed. Had him check everything out and he stated that the GP's were not the problem on her car. He cleaned the harness and reset the CEL. The light came back on before we got home! I will be replacing the harness this weekend and see if that fixes it.
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Old June 23rd, 2006, 15:11   #8
dyvyd
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Default Thanks!

Thanks to all who responded! Much more and better info than my mechanic or i could get out of the dealer . . . no surprise i guess. We'll check the coolant temp sensor and the harness and with any luck that will do it. Cheers and have a great weekend!
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Old June 23rd, 2006, 15:45   #9
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Cleaning the glow plug harness sockets with DeOxit fixed the same problem for me. The light has not been on since.
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Old June 23rd, 2006, 17:59   #10
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I get the same exact thing. I believe its the Glow Plug Harness that eventually get bad connectivity. I am buying a new one, but only thing that sucks, is you have to cut the wires and splice it your self on our models. Mine did it after the car was in the shop for a TB. Let me know if you get yours to go away. I have the exact error code.

VAG-COM Version: Release 504.1-UD

Control Module Part Number: 038 906 012 BD
Component and/or Version: 1,9l R4 EDC G400SG 2507
Software Coding: 00002
Work Shop Code: WSC 00066
1 Fault Found:
16764 - Glow Plug/Heater (Q6) Circuit: Malfunction
P0380 - 35-10 - - - Intermittent

If anyone can help me to get this to go away, otherwise I think i might buy the harness and see if it clears and does not come back. Crossing my fingers.
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Last edited by blacksheep; June 23rd, 2006 at 18:04.
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Old June 23rd, 2006, 19:25   #11
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Quote:
Originally Posted by blacksheep
I get the same exact thing. I believe its the Glow Plug Harness that eventually get bad connectivity. I am buying a new one, but only thing that sucks, is you have to cut the wires and splice it your self on our models. Mine did it after the car was in the shop for a TB. Let me know if you get yours to go away. I have the exact error code.



If anyone can help me to get this to go away, otherwise I think i might buy the harness and see if it clears and does not come back. Crossing my fingers.
Try cleaning the glow plug harness sockets with DeOxit as described earlier in this thread. Oxidized connectors seems to be a common problem that regular contact cleaner may not fix.
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Old June 23rd, 2006, 21:39   #12
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Will do vet, do I need a Vag-com to clear, or once cleaned, will go away?
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Old June 24th, 2006, 12:59   #13
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Some kind of code scanner or VAG will be required to clear the codes.
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Old June 24th, 2006, 13:10   #14
John06jetta
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I had a glow plug cel that kept coming back. so I checked the resistance on the plugs checked the glow plug relay and put some dialectric greese on the harnes and that took care of the problem for about 4-5 days. then the cel came back up, so just for the heck of it I called the dealer to see just how much one would cost. I was figuring 100 - 200 $ but to my suprise it was only 42$ so after I replaced it the cel was gone. Stayed gone until I sold it. That could be your prob. also.
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Old June 25th, 2006, 09:59   #15
Luke JettaDriver
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I had the same problem. The first time, the dealership said it was an error that wasn't flushed from the computer correctly. The second time, they recommended spraying the glow plug harness. That was about a year ago and the CEL hasn't been back. Apprently it is a common problem, according to the dealership I bought the car from.
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