Hi!

I have a question about a 1998 Toyota Starlet (EP91). For the last 18 months of so the MIL has come on from time to time, usually when the engine is somewhere between cold and normal running temperature, but occasionally when it’s been warm for a while. I finally got around to getting a warning code from it, and it came back with 22, indicating an issue with the coolant temperature sensor.

I researched the correct part to buy, and decided that Cambiare VE375145 would do the job, so bought one from ebay for about £15. After installing it, the engine appeared to run fine, but I noticed that after a driving for a few minutes, the temperature gauge was right off the scale. I stopped and opened the bonnet, but there was nothing to indicate that the engine was actually overheating.

Once back home I re-fitted the old sensor, and the temperature gauge behaved normally again. Everything seemed fine so I left it. However, this morning from a cold start it wasn’t happy at all – at best it would idle slowly for a few seconds and with the MIL lit before cutting out. I put the new sensor back in, and it burst into life with no problems. But the temperature gauge was playing up again – when the engine is completely cold it shows a cold reading, but after idling for about 10 seconds the needle is at the middle of the scale, and when at warm running temperature the needle is way off the scale again.

So now I have:

Old sensor: temp gauge works, but engine won’t start properly
New sensor: temp gauge over-reads, but engine starts

Researching these sensors a bit more, it seems that this sensor contains 2 separate thermistors - presumably one for the ECU and one for the gauge. Which suggests that the ECU thermistor on the new sensor is OK but the gauge one is not. I'm not sure if it's faulty or just the wrong model.

A genuine Toyota sensor from Camskill costs £63 while a Facet one is listed for £32 (but I haven't found one in stock yet). Have I simply made the mistake of going for the cheapest?

Edited by benjus on 17/05/2015 at 19:23