TDI90 - Engine turns over but doesn't start

Hello, hope some kind soul can offer a pointer.

2004 TDI 90 running normally until Thursday when yellow engine light came on after about 5 minutes driving. Stopped and started again and engine light came on straight away. Parked and left engine to cool down, started and light reappeared after about 5 mins. Engine running fine throughout. Started again last night, engine turns over but didn't catch but eventually ran after about 5 attempts. Stopped and started again and engine fired straight away.

Turned over cold engine again this morning and doesn't start again. Gendan diagnostic meter says 1 fault - PO118 (Engine coolant temp circuit high input). Panel says OK, no yellow coil light. Recent major service about 2,000 miles ago inc. all filter changes, battery healthy, outside air temp 5-15 degrees C throughout. Crank sensor replaced about 30k ago.

Any suggestions very welcome.
David

David,

The following is from the VCDS Wiki and details fault code P0118.

I'd suggest checking the wiring to the sensor and if this is okay then replacing it.

Hope this helps.
Steve


16502/P0118/000280 - Engine Coolant Temperature Sensor (G62): Signal too High

Possible Symptoms
Difficulties with starting a cold engine.
Starting the engine when engine is warmish or warm, idle rpm immediately is 1200 - 3000 rpm.
RPM at idle is irregular.
With all engine temperatures idle rpm will often vary between 900 - 1000 rpm.
With engine warm (90 °C) the engine temperature suddenly drops (70 °C) and slowly comes back to 90 °C.
Bad acceleration during warm-up.
Diesel Engines: Glow plug indicator may be on for a longer than normal time or at ambient temperatures where it shouldn't come on at all.

Possible Causes
The electrical signal coming from G62 is too low
Wiring and/or connections faulty (short circuit?)
Engine Coolant Temperature Sensor (G62) faulty

Possible Solutions
Check wiring and connections
Check / Replace Engine Coolant Temperature Sensor (G62)

Special Notes
In many cars between MY 1995-2002 the G2/G62 had a bad reputation for failing often. The original G2/G62 sensor is black and the improved replacements are green.

I love this site. Thank you very much - those symptoms look very familiar. I'll try changing the sensor.

Well, engine coolant temp sensor replaced and works fine, thanks for the suggestion which was spot on. Although I wouldn't have thought that a new temp sensor would have much of an effect, if any on the ECU, the engine fired up immediately straight away for a couple of warmish (9 deg or so) days but yesterday took a lot of starting as before. Next stop, VAGCOM data. Suspect glowplugs - only ever replaced one - or cam sensor which was replaced at 65k and now at 107k.

Three glowplugs replaced and all's well. I couldn't match the plug type to my A2 on the Bosch website so I used NGK Y-607AS -(3 for £27 from 'Mr Solutions' on ebay) - as the NGK website does matches the plug to the vehicle. Fitted using a 4" 10mm box spanner with a hex socket in the other end connected to a socket and extension to torque wrench - 15/20Nm. I greased the threads as they are a snug fit and it's easy to strip threads in soft alloy block.