01 ALH Jetta Glow plug issue

I've been getting an intermittent P0380 CEL, but mostly when cold. I have the two wire glow plug harness and cleaned the contacts and the CEL wouldn't come on for a while, so I cleaned the contacts again and I was still getting the CEL intermittently. So I replaced the Glow Plug Harness and again I went a time with out the CEL, each time I think I've fixed it and hadn't. So I finally had a buddy around to run the multimeter for me and check for voltage at the harness, I was unable to get the desired 12Vdc at the harness. I looked at the Fuses on top of the battery and they all look and check good. I thought all that was left was the 180 relay, I ordered it and replaced it, still no joy. I'm getting the P0380 CEL about 3-5 minutes after start up. I've never had the toe kick panel off and while replacing the relay I see a few terminal studs, most noticeable to me was the 87F/Diesel terminal that is empty. I looked for a loose/floating terminal and didn't find anything, however on the most center terminal with a 30 on it there are two terminals bolted down, I'm asking if this is normal or if someone was monkeying around before I owned the car and if there should be power on the 87F/Diesel Terminal post? Also, which fuse on top of the battery should be suppling the power to the 180 relay? http://pics.tdiclub.com/showphoto.php?photo=108240&title=diesel-terminal&cat=500

I'm thinking that maybe I have a compound issue, I replaced the 180 Relay and still didn't get any power at the harness. So going back to the start of the troubleshooting, I disconnected the Coolant temp sensor and then turned the ignition switch on, this time I got a glow plug light for almost 30 seconds. I disconnected the glow plug harness and put my 12vDC test light on one of the GP connections, when I turn the key on, it illuminated and stayed on a little past the time that the GP light on the dash went out. I believe that I have it trouble shot down to a bad coolant temp sensor now, correct? So perhaps I had a bad relay and a bad coolant temp sensor?

If you're getting 12V at the harness, then your relay is good. The GP harness will get power even after the GP light turns off, this is normal. If you get power at the harness with the coolant temp sensor unplugged, then yes your coolant temp sensor is most likely the issue here.

Trouble continues

I replaced the relay and tested the system, the glow plugs still won't come on. If I disconnect the coolant sensor, my glow plugs come on for a while, so I replaced the temp sensor, but with the new sensor installed and hooked up the plugs didn't glow and the engine was slow to start. Was short on time so I wasn't able to disconnect the temp sensor and see if the glow got initiated.

Here's where I need help, what the heck else is there to replace or check? I have a VAGCOM, but haven't used much, so I may need pointed in a direction of what to look at with it, if there's something I can test.

Thanks again for all the help

I'm having the same issue with my ALH Vanagon.......... I hope in a few days I can find the time to dig in and see what's going on!

I'm suspecting it is a wiring issue in the Temp sensor circuit(s), or, the connection is corroded in the plug!

Finally got a little more time to work on the Glow Plugs, and I'm getting more frustrated. Current status is, with new coolant sensor disconnected I get a 15-20 second glow. I have tried to check the wires from the sensor to the ECU, but am not having any luck. My copy of the Bently shows the 4 pins of the sensor, I believe that I'm looking at T80/54 and T80/70 that goes through the coolant sensor, but I'm not able to get continuity between the sensor and the ECU. Can anyone confirm the wiring? I believe that it is going to the bigger of the two connectors on the ECU, and I can see the numbers on the ECU so I believe that I'm counting the pins correct. I have trouble reading the schematics in the Bently format, I like pictures better. Any help is appreciated.

I do not have my Bentley at my side that covers the 2001 Jetta, but, I do have the Bentley that covers the 2001 New Beetle and my Ring Binder of schematics from the Bentley that covers the ALH engine from September 2001. Thus, they are the same and do cover your car.

Both of those references show that the ECU is the 121 pin unit. So, on that basis, here is what I can offer..

Both show the same: The CTS is G-62 and G-2 (as one unit) ... G-62 is composed of Pins 4 and 3. Pin 4 goes to T121/112 on the ECU and Pin 3 goes to T121/104 on the ECU .... both reference sources are the same!

G-2: Pin 1 on the CTS goes to the Cluster at T32/8 and Pin 2 goes to Splice 269 in the instrument panel wiring harness. Splice 269 is a common ground for a number of other gauges/sensors, such as, fuel level, multifunction indicator light, washer fluid level, outside temp sensor, etc. The actual ground for Splice 269 is at/in the Cluster at T32/7.

(Note T32 is the Blue connector on the back of the Cluster and T32a is the Green connector.)

Here is a pic from the Bentley schematics for the 2001 & 2002 model ALH engines in the Jetta.

AndyBees, Thank you for your very detailed information. I have a electronic copy of a Bently and it shows the T80 for the ECU, but that didn't make any sense to me last time I tore it apart, So today I finally have time to dig back into the car and try to resolve my issue. I will let you know if the T121 makes more sense and works out for me.

My current status is I get the glow period of about 15-20 seconds with the ECS disconnected, but when hooked up I don't get any glow period. I clear the P0380 code what seems almost everytime I start the car (my GPS has a OBDII plug on it for MPG's) The P0380 code comes up even when the engine is hot, so I'm really starting to wonder what is going on. Any insight from the TDI gods would be helpful.

When you changed the harness, did you go right back to the 2 pin connector under/behind the air box in the plastic duct, or did you cut and splice near the engine? It may be that connector is no longer making reliable contact and needs to be cleaned or replaced.

Check the readings of the CTS cold, then check it hot.

Alchemist, I did splice near the engine. With the car apart today I checked the 2 pin connector behind the airbox and it was clean and looked like a solid connection.

BobnOH, With a cold engine I get an open reading at pins 104 and 112, with the CTS sensor hooked up, I checked continuity and it is good between from 104 to pin 3 of the CTS and 112 to 4 of the CTS. I left my leads in 112 and 104 of the ECU and shorted pins 3 and 4 together of the CTS and got continuity. So in my head, my wiring is good between the ECU and CTS, but I'm not sure that I'm supposed to get an open with a cold engine. I guess I'll warm the engine and see what happens at 104 and 112. I got another CTS and it gave the same results. Maybe the connection at the CTS is faulty, but it looks good.