2001 Jetta TDI problem with check engine light

[nmudd]

I have a 2001 Jetta TDI with about 85000 miles on it. The check engine light came on at about 80k and I took it in to the dealer. The diagnostic tool gave two erro messages - 0380 and 1248. The dealer said that 0380 mean that the glow plugs could be faulty and causing both errors. I tested the plugs, found one bad, and replaced the plugs. This stopped the ligth for a while but it eventually came back on. It would stay on a little while and then go back off but this kept repeating until eventually it starting staying on all the time. The car drives fine and still runs great. When I looked the error message up in my service manual it called it the Injection Start Control Deviation. Does anyone know what could be causing the error? I have looked around online and found a few things that it might be (faulty relay and clogged intake manifold) but none of the symptoms completely match what I am seeing. Can anybody help?
Thanks,

Nick

[veedubmechanic]

Sounds like your injection timing is off too far. Since the injection pump is adjusted manually the computer cant compensate for slack in the timing belt so it sets a code for "start of injection". If you havent replaced the timing belt/tentioner/rollers/water pump yet, your should deffinately replace them soon.

[nmudd]

We have gone through a cold snap here in Georgia and I noticed a little bit of a pattern in the check engine light. It stays on constantly during warm weather, but when it gets below 45 degrees at night the light doesn't come on after a cold start until the engine reaches the normal operating temperature. There seems to be a "sweet spot" of sorts as this only happens when I start the car cold and the outside temp is somewhere between about 30 and 45 degrees. I the outside temp is warmer or colder the light pops on about 10-15 seconds after starting. I had the timing belt replaced at 60k miles (it is a 5-speed).

[veedubmechanic]

Well glow plugs and there harness go bad on EVERY tdi after 50k miles.
ALso the relay sometimes goes bad. If you have a 5 speed there is a glow plug trio on the right side of the engine. Those are used 2 heat the coolant to bring the temp of the engine up faster because there is no coolant going through a transmission (AT cars). Check the glow plugs on the trio next to the valve cover and those harnesses. If you see any copper color on the harness you need to replace the harness.