[SoxFan]

I have a 2002 Jetta TDI 5 Spd with 72K miles on it (I bought it new). I have had a CEL on for a while now. It is the glow plug for #4 cyl according to my code reader. I don't have a garage so I thought I would get to it when the weather got a little cooler. (that's coming up soon).

But last week it developed another problem. It will start but not run. I connected my code reader to the OBD II port, I can read battery voltage but can not communicate with the car..
Other symptoms, I turn the key to the run position and none of the LCDs come on (odometer, clock etc), warning lights do come one (CEL, battery etc), power windows don't work from the door switches, but they do work with the key inserted into the driver door (all go up, all go down). The radio does not come on. It is an after market radio but it has been in the car and working for 6+ years and I have been able to use the code scanner up until this time.

I did a bunch of searching on this site and many others and there are 2 very common suggestions. The 109 relay and the aftermarket radio.

I've replaced the 109 relay with a new one and since the radio has been in over 6 years I would think a problem with the radio would have shown up before now.

I thought maybe the ignition switch but I don't hang a bunch of key on my ring, just the ignition key so with 72K miles I thought it was unlikely.

Since this car has been fairly trouble free with the exception of the heated seat fire, leaking sunroof, failed radio antenna I haven't had much need to go digging around. Thought it might be worth consulting experienced mechanics to figure out some places to look before I pull out a wiring diagram and tracing wires.

Thanks in advance for any help or suggestions

 

[David A. McDow]

Check your battery. A carbon pile tester is best (most Interstate Battery stores have them). I had all kinds of intermittent problems with my airbag light coming on, odometer reading not showing up, etc. One day the car wouldn't start. Took the battery in for testing and it was bad. Put a new one in, cleared codes, and no more problems with the dash.

 

[SoxFan]

Check your battery. A carbon pile tester is best (most Interstate Battery stores have them). I had all kinds of intermittent problems with my airbag light coming on, odometer reading not showing up, etc. One day the car wouldn't start. Took the battery in for testing and it was bad. Put a new one in, cleared codes, and no more problems with the dash.

Thanks..... I actually got home from 3 weeks of travel and went back to troubleshooting.... found the LCDs (odometer/clock) on again, windows, locks, radio all good but not enough power left in the battery to turn it over. Put charger on it for a while but only got to 40% and the charger indicated the battery was bad. Took it in and had it tested. Bad cell. Replaced it and all seems OK. Haven't had a chance to take it out for a good test yet but I am hopeful. Strange though, because it fired right, not slow crank or any other abnormal indications just wouldn't stay running.

Glow plugs arrived today so I still need to replace the one on Cyl 4 at least. The ignition switch should be here tomorrow. Might replace it at some point, but no rush now.

 

[UhOh]

Check the operation of your ASV [Anti-Shudder Valve in the EGR]. If gummed up they can stick in the closed position: they're supposed to only temporarily be closed to help stall the engine at shut-off; vacuum is dropped and they are supposed to return to their default position of being open). No air means the engine might pop but then not really run because it isn't getting air. IF the ASV is sticking you might be able to help it by manually working it (move the lever that attaches to the vaccum rod): if it has been found to be sticking it is most likely that the intake and rest of EGR is gunked up an in need of being cleaned; freeing up the ASV will at least help with starting.

Pre-soak glow plugs before attempting to pull them. Warm engine up a bit first. Best to use a T-handle wrench to reduce shearing force that a normal wrench tends to impart: GPs are pretty fragile. I just ran across someone who has an engine with a broken GP: I'm trying to figure best course for them to take- leave it, doesn't get extremely cold here, or take it to a shop I trust (but might not want to touch it). Suffice it to say, you do NOT want to break a GP. Don't force anything here.

 

[SoxFan]

Check the operation of your ASV [Anti-Shudder Valve in the EGR]. If gummed up they can stick in the closed position: they're supposed to only temporarily be closed to help stall the engine at shut-off; vacuum is dropped and they are supposed to return to their default position of being open). No air means the engine might pop but then not really run because it isn't getting air. IF the ASV is sticking you might be able to help it by manually working it (move the lever that attaches to the vaccum rod): if it has been found to be sticking it is most likely that the intake and rest of EGR is gunked up an in need of being cleaned; freeing up the ASV will at least help with starting.

Pre-soak glow plugs before attempting to pull them. Warm engine up a bit first. Best to use a T-handle wrench to reduce shearing force that a normal wrench tends to impart: GPs are pretty fragile. I just ran across someone who has an engine with a broken GP: I'm trying to figure best course for them to take- leave it, doesn't get extremely cold here, or take it to a shop I trust (but might not want to touch it). Suffice it to say, you do NOT want to break a GP. Don't force anything here.

The battery seemed to clear up the issues (other than GP that I knew about).

Have to replace it to get the CEL to go off before inspection. Thanks for the suggestion of soaking and T wrench.

 

[UhOh]

Do a quick test of the GP itself before committing to replacing. Sometimes it's just the connection: I had a CEL pop up for a "bad" GP but the GP tested fine; I ended up stuffing some aluminum foil on top of the GP tip/connection and then seated the harness connector on it and that kept it working for years.