Passat 3BG 1.9 TDI not starting/won't start due to glow plug issue

Dear community,

After weeks of unsuccessfully tinkering, I'm hoping to find some help here. My Passat (manufactured in 06/2003) no longer has a glow plug light illuminating; the bulb goes out after about half a second. Consequently, it starts very poorly. Here's some background information and what I've tried so far:

The problem first appeared after the car had been sitting in the workshop for a longer period and the engine had received a new camshaft, lifters, and timing belt. The mechanic insists that he adjusted everything carefully and correctly.

If the connector for the temperature sensor G62 is disconnected, the engine will normally glow (for about 8 seconds?). The same applies when the G62 is treated with refrigerant spray. Furthermore, VCDS shows a preheating time of 0.00 in block 12. As a side note: Since then, the coolant temperature has not risen above 60 degrees Celsius, even on highway driving. This could also be due to a faulty thermostat that coincidentally failed at the same time.
Previous measures:
- Spark plugs replaced.
- Replaced glow plug relay.
- MSG swapped.
- Coolant temperature sensor replaced.
- Checked glow plug fuse.

I'm at a loss now. What else could be the cause? Could it be corroded grounding points? Or faulty cable connections?

Thank you very much for your help!

Autoscan?

The auto-scan shows no error codes for modules 01, 03, 15, 17, 19, only existing error codes for modules 08 and 46.

I just remembered something else. During the multi-week stay at the workshop, an error appeared with the airbag sensor because the sensor was flooded (the drain under the battery was blocked). It was replaced, and since then, that warning light has been off.

And it does glow!
At an outside temperature of -3°C, (block 12) shows G81 at -1.8°C, G62 at +4.5°C, and a preheating time of 1.33. The engine started relatively easily after approximately 1 second. After about 1.5 minutes, the relay clicked, and the glow plug status changed from 01010000 to 11111111.

It's good that the glow plug system seems to be working, but I haven't made much progress. Why does it start well in cold weather, but do I have to crank it for several seconds when it's only 10°C?

It's a known issue. Please search for "warm start problem" in the relevant publications here.

At higher temperatures, the engine speed must be increased before fuel injection is allowed.