keep getting "Glow Plug electrical fault" and MIL

[fuse]

2002 Jetta tdi, have had it for three years running almost exclusively on 100% biodiesel (B100).
About a year ago, I had the MIL come on, and using VCDS-Lite, got the following:
17057 - Cylinder 3 Glow Plug Circuit (Q12): Electrical Fault
P0673 - 35-10 - - - Intermittent

Checked the resistance, and it indicated it was bad, so I replaced it. Everything was fine and dandy, until a few months later, when I got the same thing, but this time two other glow plugs were bad, so I replaced all three old ones.

Everything was fine and dandy, until last week, when I got the original fault code. Now I'm wondering what the problem actually is.

Does this code indicate other problems that are simply not listed on VCDS? I understand sometimes you need very specific scan tools.

ALSO: I have noticed that when I can sense slight clogging in the fuel filter (it's very subtle, but i ran an old Mercedes on home brew and straight used oil for 6 years), these codes seem to come on a little while later.

If the car is run for an extended time with a slightly clogged fuel filter (not bad enough to affect idle speed or starting - just enough to make acceleration ever so slightly less than a good filter) would this affect electrical issues, like glow plug voltage? Do TDIs have a warning light/fault code for a clogged filter?

Any insights much appreciated!

 

[JB05]

All of my GP related DTC's get corrected by cleaning the harness with DeOxit. Try this; you can get it at Radio Shack.

 

[PDJetta]

Fuel filter clogging is not related to the CEL and/or code for glow plug electrical faults. There is no monitoring of the fuel filter by the OBD II system, and thus that won't set a code/CEL.

Measure the resistance of each of the glow plugs again. They should be very close to the same values, or you will get a code and if off enough, or if the fault occurrs frequently enough, the CEL will illuminate.

If the GP resistance values are the same, all the plugs are good. The next most likely cause of intermittent GP fault codes is poor connections where the harness plugs onto the glow plugs. This connection can sometimes have enough resitance to throw a code. There is a long thread on this list about GP codes and poor wiring harness connections. This is a well documented problem that is fairly common with older TDI. I have experienced it on my '04. Basically, you need to clean the GP contacts and the ones in the harness and if that does not solve the problem, replace the GP harness. The GP relay seldom causes problems, but it is not unheard of.

--Nate

 

[Mike_Van]

+1 on suspecting the GP harness (i.e. poor contact with one or more of the GP ends).

 

[Vince Waldon]

And remember that on early TDIs like your 2002 the glowplugs are numbered in reverse order... #1 is on the drivers side etc etc etc.

 

[fuse]

Thanks guys. I used electrical contact cleaner on the harness, but did not solve it. Is DE-Oxit really that good?

 

[Ol'Rattler]

Yes, it is an excellent product but it may or may not fix your problem.

 

[JB05]

I 've used some electrical contact cleaner from HD, but I had to apply it every other month or so. When that ran out I splurged on the DeOxit and one application has lasted several month. One can is a cleaner and the other spray can puts a protectant coating on the contacts.

 

[Vince Waldon]

Here's my experiment on a permanent fix for harness shenanigans:

Turns out the tops take an 8/32 thread nicely:

No more "time to DeOxit the glowplug harness":

 

[mecne]

Here's my experiment on a permanent fix for harness shenanigans:

Turns out the tops take an 8/32 thread nicely:

No more "time to DeOxit the glowplug harness":

Curious , what the connection looks like on the other end?

 

[Vince Waldon]

Curious , what the connection looks like on the other end?

I tapped into the wiring duct that runs behind the airfilter, just upstream of the glowplug harness plug, leaving it in place just in case I (or someone else) want to revert to the OEM harness:

Stripped off an inch of insulation, soldered on the new 10 ga wires, and then two layers of electrical tape for insulation and vibration damping.

 

[PDJetta]

Nice! And you save the price of a new GP harness

--Nate

 

[XXX_er]

NICE! ^^

to the OP replacing the plugs & harness & do the contact cleaner enhancer all at once fixed my problem, basicly there are multiple combinations of 5 parts that can fail

 

[TC282AVIATOR]

Nice job, respectable resolve . I have yet to find Power getting to my glow plugs , replaced the relay and fuse bar at the battery are intact. was going after the temp sensors next , anything I am missing ??

 

[Genesis]

The harness itself is likely open internally.