P0673 Code on my 2012 Jetta Sportwagen

[tims19]

Good afternoon, everyone. My 2012 Jetta Sportwagen is throwing a P0673 code:

001651 - Cylinder 3 Glow Plug Circuit (Q12)
P0673 - 000 - Electrical Fault
Freeze Frame:
Fault Status: 01100000
Fault Priority: 2
Fault Frequency: 1
Reset Counter: 255
Mileage: 165750 km
Time Indication: 0
Date: 2050. 14. 31
Time: 15:07:25

Freeze Frame:
RPM: 2415 /min
Speed: 0.0 km/h
Voltage: 13.76 V
Temperature: 7.2`C
Bin: Bits: 10110000
Time: 2.52 s
Temperature: 8.1`C

All my searches on this particular code have led to instructions on testing and replacing glow plugs. My glow plugs all check out fine. They were resistance tested both in and out of the vehicle and all four show equally low resistance. Connections to the plugs seem to be okay as best I can tell. I have also inspected the wiring harness (both visually and with continuity tests where possible) and can find nothing unusual.

MY questions to you are:
1) Can this code be pointing to a problem in the glow plug control module?
2) Are there "likely culprits" I should be looking for in the wiring harness or elsewhere that may not be obvious?

I would appreciate your thoughts.

 

[turbodieseldyke]

You should swap the plugs to different ports. If the same error occurs, then you have a wiring problem. If the error moves to another cylinder, then the glow plug is bad.

 

[tims19]

Thank you. Yes, I tried that as well. Sorry for not mentioning. The problem stays with #3.
I'm wondering if there particular known weak spots in the harness I should focus on.

 

[turbodieseldyke]

Supposedly down behind the oil filter. Most people will tell you to just replace the whole harness instead of cutting it open & hoping to find a clearly broken wire.

 

[tims19]

I'll take a closer look in the area of the oil filter, for sure. I would certainly be willing to go the route of harness replacement. I noticed that some of the plastic guards on the glow plug connectors were broken, which raises questions, for sure. I had actually searched to get an idea of cost, but I struggled to find a replacement harness. Anyone know where I can get a harness at a reasonable price?

 

[turbodieseldyke]

They sell replacement plastic clips for the glow plugs.

 

[borninabus]

so....if you switched the wiring plugs and the problem remained in the same place, that would be indicative of a fault with the glow plug itself. the idea is that when you move the wiring, the problem also moves with the faulty wiring.

 

[tims19]

Sorry, to be clear, I switched the glow plug locations, not the wiring plug locations. I kept the plug connectors at the same place, but I rotated the glow plugs from #1 to #2, #2 to #3, etc. In other words, even with a different glow plug (one from a previously working location) in cyl #3, the problem stayed at #3. That would seem to verify that it is a wiring issue. My apologies if I didn't explain myself properly on that detail.

Here's another question, though: All four of my glow plugs are identical. Videos I've seen in my research indicate that #3 is a typically a pressure sensing plug and the other three are standard glow plugs. Is it possible that is my problem? I bought this as a certified used car from a Volkswagen dealer, so I would expect everything to be as it should in that regard. Are all 2.0's supposed to have that pressure-sensing plug or do some not have it?

 

[tims19]

Is anyone able to comment on my question in bold in the above post? How do determine if my Jetta is supposed to have that pressure-sensing glow plug in position #3?

 

[oilhammer]

All four of your plugs are the same pressure sensor integrated type.

You have a bad connector or engine harness. You can buy the little clam shell pieces by themselves, and you can buy the connector by itself and splice it in with the proper type connectors and tools. However, these were all on backorder last time I checked, and that assumes that the wire problem is close to OR in the connector itself. Often times there is something gone wrong further up the harness. And if that is the case, you'll eventually have other problems, too. In that case, it is best to just get a new engine harness through your local dealer and replace the whole thing. This is a BIG job, and requires taking some stuff apart for proper access, and there are a few things I do to help keep it from possibly happening again.

 

[tims19]

Thank you, Oilhammer. Much appreciated. I guess I should have realized that the glow plugs were ALL he pressure sensor type based on the size of the socket I needed to remove them, so that makes sense. I should have taken a closer look at them when I had them out. Anyway, I did take a look at what it would take to replace the harness and I have no doubt that it would not be fun at all! I think I'd like to start with replacing the #3 connector as a just-in-case approach. That may buy me some time and the investment is minimal to do that as a first try. I'm perfectly capable of doing that splicing, BTW. I have skills and an overabundance of good tools! Do the glow plug wires go all the way back to the glow plug control module/relay or are there other system components/connectors in between? I'd like to make sure that I'm looking at all of the other likely weak links as well.

 

[oilhammer]

The glow plug wires, at least the plugs themselves, not sure about the pressure sensors, jump out of the engine harness and into the car harness at the connector near the driver side headlamp, sort of under the air cleaner... and through that harness go to the glow controller under the underhood fuse box.

 

[tims19]

Great, thank you. I should be able to get to those areas with only some minor disassembly, so I'll take a look at those connections for anything obvious.

I'm also curious if the P0673 code can indicate a problem with the glow plug circuit OR the pressure sensor circuit or if an issue with the pressure sensor circuit would throw a different code?

 

[turbodieseldyke]

The pressure sensor throws a different code, P13Dx, with x varying by cylinder#.

 

[tims19]

UPDATE: I ordered a replacement glow plug connector for #3, but it did not yet arrive. So, this past weekend, in an effort to cover all my bases, I took some time to access both the connector behind the headlight and the glow plug relay.

I cleaned all of those connections thoroughly as well as the glow plug connectors and the electrical end of the glow plugs themselves. In the process I also discovered a ground cable that had been attacked by a rodent of some sort (the insulation was chewed off, but the conductor was still very much intact), which I cleaned up and re-insulated.

In the end, the code went away and has not returned! Fingers crossed that it stays that way (confidence is at about 30% on that one), but we'll see. Thank you all for your help!

 

[oilhammer]

Awesome! Fingers crossed with ya!

 

[tims19]

Well, the #3 electrical fault code returned and he brought a new friend, the #1 electrical fault code! I started by cleaning the glow plug connectors with contact cleaner, then some CRC 2-26 spray. I erased the codes, but they came right back. Next, I did the same for the harness connector behind the headlight. This time, I erased the codes and they did NOT return. Everything has been fine for a few days now.

I'm not 100% convinced that I have isolated the problem (we all know how frustrating intermittent electrical issues can be!), but hopefully, I'm on the right track.

Here's my latest question to the group: Years ago, there was something called "Cramolin R-5", which was a contact protector the worked extremely well. It only took a tiny amount and it would migrate on the connector surfaces, so it lasted forever, even on connectors that moved a lot. Unfortunately, that disappeared when they banned certain types of propellents in aerosals. I don't have near as much faith in the CRC product. Can anyone recommend a contact protector that works (hopefully) as well as the R-5?