[locolobo]

Friends, I received code P0671, indicating open circuit on glow plug one. I ordered a set of glow plugs and took off the intake manifold. Upon testing glow plug 1, 1st in the front, it is not open circuit after all. It tests the same as all, about 0.4 ohm. I turned on the ecu / key and checked the output of each harness. They all read about 4.0 volts. With everything plugged in, it's still showing code P0671. I am not going to put it back together until I solve this. Any ideas? Thanks!

[GreekboyD]

Could it be a problem with the glow plug control unit?

[locolobo]

GreekboyD that is what I suspect; there are not a lot of other possibilities I know of. From what I have read on here though, when the controller fails, it normally shows all 6 as open.

[GreekboyD]

Originally Posted by locolobo

GreekboyD that is what I suspect; there are not a lot of other possibilities I know of. From what I have read on here though, when the controller fails, it normally shows all 6 as open.

It's the only plausible thing left. How did your intake look in terms of carbon? I was amazed at how many things need to come off just to install the glow plugs when we changed them (and the control unit) two months ago for my buddy.

[locolobo]

It looks pretty good. Only 47k miles; I have had it since 32k. I am using B5 fuel all the time. There was some buildup on the swirl flaps, 3 mm on the EGR valve stem...not too bad, not enough to cause any problems. I'm going to use a bottle brush and some Chemtool to clean the ports I can reach, but I'm not worried about the big chamber area at all.

Even though the glow plugs are OK, I guess I will replace them anyway while it's taken apart. But, that's another $200 maybe I don't have to spend. How long are they supposed to last?

Since it will be a few days until I get the controller installed, I was debating whether to remove the swirl flaps. They don't seem loose or damaged, just a place for carbon to build up. I have read that removing them has no adverse consequences.

[kpm]

About a year ago I had just a single glow plug cylinder 3 faulty code come in at 67,000 km(41k miles). The dealer replaced the one glow plug and not long after the light was on again with the same fault code. This time they replaced the glow plug controller and no problem since.

[locolobo]

Thanks KPM for the vote of confidence. Controller is on its way. I figured when I checked them and none were actually open circuit, it had to be the controller. I wonder if the dealer actually checked yours before replacing the one plug? Probably not.

[kpm]

Yah, I recall discussing with SA on the second visit and because the fault only came up for one plug they were only authorized to replace the one glow plug under warranty. It took a repeat to get the real culprit, the controller.

One thing I have noticed having gone through one winter with the new glow plug controller is a noticeable operational difference versus the original. During the first three winters of ownership it was rare to see the glow plug indicator light on and when it did the on time was so short, it was hardly ever noticed. Having racked up some serious mileage on a couple of late 70's Peugeot diesels where you manually controlled the length of glow plug operation and also a 2000 Jetta that auto controlled the glow plugs the based on outside temperature, the Jetta on time was noticeable variable. With the new controller on the D... the operation of glow plugs was actually on for 2-3 seconds at times during the extreme cold but was for the first time noticeably varying the length of operation as it should by design. Recognizing it was a colder winter this past year which may rationalize some operational difference, it still makes we wonder whether the original was ever working properly.
Also, Just an fyi as you mentioned you were also replacing your glow plugs....not sure if the gaskets can be re-used or if you ordered but the warranty glow plug replacement did include replacement of two different profile gaskets(six of each type).
Good luck and hopefully you found the right culprit.

[locolobo]

I installed my parts today. Getting that glow plug controller out was a miserable task, not much room to work. It's a terrible design to put maintenance items / consumables under the intake manifold. In my Jetta TDI this job took 20 minutes. Anyway I took several cursing breaks and rested. I had to pry the big connector off with a flat blade screwdriver, since squeezing the tabs did not work. Replaced all 6 glow plugs even though they all tested OK, again just because I have it all taken apart. I have new gaskets for the intake, but I'm now considering replacing the thermostat too and any other maintenance items before I reassemble. Luckily, I have a backup vehicle so I can take my time.