Glow plugs/coolant temp sensor issue

I do apologize if somewhere this was already discussed, I did try to look through the glow plugs 101 thread however 115 pages does not make it easy. I have a 2000 auto Jetta. I just put all new plugs, harness, and coolant temp sensor on the car. Plugs are bosch and harness and CTS are oem VW. With my CTS plug off I get good 12v at every plug however with it plugged in I'm getting nothing. I even hooked up my old CTS and still got nothing. I find it ultra hard to believe that I have two bad oem VW coolant sensors especially since the one is two weeks old. I've tried to do more digging but can't find anyone with this problem. Any help would be greatly appreciated.

Did you check the wiring leading to the cts?

Visually everything looks sound. Do you know what for readings I should be getting from the plug at each pin? Or even which pins on the sensor itself to see by some miracle I managed to just get two bad ones.

What temp is the car at when your trying to do this?
If it's well below freezing you'll get maybe 2-4 seconds before GP light goes off.
If it's around 40 and above the GP light will blink then shut off.

The reason you can read it with the CTS disconnected is the ecu thinks is -30f or colder and will give you I think 12 seconds of glow plug.

I was actually waiting until this evening to run my own theory along the lines of exactly what your talking about. Friday night here it was 16-18 degrees and I'm guessing 20ish when I tried to start it Saturday morning which I got my usual glow light blink and that's it, it was a bear to start and sounded like crap. Tonight I pulled my second CTS out of the freezer I had it in for 24 hours which I laser temped it at -7, stuck it on the car and bam had maybe 6-8 seconds of glow. Now you can't tell me that VW designed this glow plug system to only work at extreme temperatures like I recreated. All my diesel truck systems will fire off even in the mid 30's and when they start they sound respectable.

You have the older 2 wire glow plug system, as Steve says it stays on longer the colder it gets. The glow plug writeup should tell you what voltage you should get, without looking I believe it is 12v.

There is one other thing you haven’t said you changed out and that’s the 180 relay (glow plug relay). On your car it will be in the fuse/relay panel under your steering wheel. I kinda doubt that is the problem though.

If you have vcds you can extend the glow plug cycle so it stays on longer.

Yup you're right the two wire system, as I just put in the brand new harness. And also yes 12v is exactly what I get when I A: have the CTS unplugged or B: have the sensor itself in my freezer at -7. Like I said I just can't by off that my system won't fire off when it's 20ish and only when it's a ridiculous -7. Your also correct I never checked the relay because I assumed that is working correctly because I'm getting power where I should, just not when I should. I unfortunately don't have the vcds system, I thought about it, just seemed a bit pricey.

I have seen injection timing cause similar issues to this. The car would not start well cold without running the glow plugs a lot, sensor unplugged. Put it in time and it fired flawlessly.

They changed design of the lower crank sprocket on the early models like yours because the sprocket key would wear and allow movement.

As discussed, if the CTS is bad or disconnected, the ECU defaults to -40c (minus 40). Which will make the GP relay kick-in and fueling will be increased. VCDS will show this to be true.

Also, even at 90f ambient temp and a hot engine, you'll momentarily see the GP light when ignition is turned on. However, the relay did not glow the plugs (take a relay apart and you'll see why).

I don't think the 2000 ALH has the crankshaft/pulley issue. As I understand, that was on earlier models (maybe AHU engine). However, proper timing sure makes a semi-cold engine start much smoother.

Here is a link to discussions about the earlier (pre-ALH) engines with crankshaft nose issues: http://forums.tdiclub.com/showthread.php?t=75793

Yes that's exactly what mine always does, just a momentary blink, but confirmed no voltage at the plugs. Can my timing be adjusted through this vcds or just monitored? Also is that something I should have the dealership look at or just find someone who has vcds and is good with it?

TripXAnarchy99, the only way to set timing is with the use of the VCDS. With engine temp at 85c or higher, VCDS will show where the timing is. Then, you have to loosen three bolts on the Injection Pump Sprocket (timing belt cover off) and use a 22mm wrench to move the Pump Shaft ever so slightly to change/set the timing. Counter clockwise movement of the shaft retards the timing. Clockwise movement advances the timing. IMPORTANT, very minimal movement changes the timing significantly. Generally, it takes several attempts to land the timing in the sweet spot. Each time you make an adjustment, the three bolts have to be tightened. Once they sweet spot is found (high side of the band in the graph, advanced), then you torque the bolts per spec. (Never loosen the 22mm nut on the shaft.)

Sorry the names Andrew, never introduced myself. Well thanks for all that helpful information, I may try that route and see if the timing helps. If not I'll just put a block heater or frostheater in and be done with it. Is the vcds locator thread still a good place to find someone local with the program?

I just adjusted my daughters 01 Beetle last night. She has been experiencing long cold starts. The timing was below the center of the graph now it’s slightly below the top line. The start was much easier this morning. Glow plug time (via vcds) had even been extended on her car back when she had another issue.


If you’re going to own a vw then you need a vcds. A vcds is so much less money wise than anything else out there and it does so much more than those cheap Chinese crap readers.

Very well. According to the Ross tech site I assume the hex-v2 for $199.99 is all I need? I believe it said it came with the software and everything.

If you can make sure the mechanical timing is set first, then use vcds to set final timing.
You can mask a bad timing with adjusting the pump, just my .02

Thanks for the tip on the timing. Unfortunately I'm going to have to do some more digging as I just drove it this morning and now it's throwing a pP0380 "Glow plug heater/circuit A" which is disappointing because it has brand new plugs and harness which are the high fail items and I also didn't have the fault before I replaced them.

If you used butt splice connectors to splice in the new harness, make sure that they are tight and the boots are on the glow plugs correctly

Thanks, I'll double check them. So far I drove it home yesterday and then back to work this morning and no code again. (About 40 miles one way). On a good note I started it this morning in the upper 20's and I got maybe 2-3 seconds of glow time so maybe it was the plugs/harness and it just needed to be drove to reset the system or something?