Grand Cherokee. What is the 'Coolant Sensor' ?
 

My otherwise perfectly reliable Grand Cherokee 96 woke me up on the highway three days ago with a 'pling - pling ...' and "Coolant sensor kaput". Happened a couple of times within half an hour. As the coolant level and the temperature on the gauge was perfect I have kept driving and the 'message' has not returned.

What is the 'coolant sensor' and why would it alarm me a few times and then give it up ?

Thanks!

4.0 litre 6 or V-8?

You're probably talking about the coolant temperature sensor, they're relatively easy to replace on all models. Did it generate an error code? I've still got my manual, let me know if you can pull the code.

Coolant sensor could be EITHER a low-coolant-level OR over-temperature. I think the low coolant sensor would be a better bet. As the coolant levels rise and fall due to temps, it can fall just below the level where the sensor 'sees' coolant in the reservoir. If it is the 4.0L I6 please check for weeping coolant from the bottom of the water pump; it is very common and can cause a slow loss of coolant. Eventually the pump needs to be replaced. Here in the US you can get an indy tech to do the entire job for about $200.

Thanks for replying! It is a V8 (I wouldn´t touch anything that hasn´t got either a V8 or a flat 6). ;)

I only got a 'pling' sound and the text reading something like 'coolant sensor out of order'. No code. Can I retrieve a code from that electronic box from hell ?

Thanks! I actually replaced the pump a few months ago as had started to leak as you describe. But then, when the coolant level went below the mark it said 'coolant level low'.

Ah! Now I get it. The very sensor that check the level has gone kaput! No worries then, if I just keep track of the level manually, right?

Yup. Gimme a sec and I'll look it up...is your Check Engine light on?

It's pretty much what the name implies. It could be the sensor giving up the ghost, or loose/faulty/grounding wiring. Checking is pretty easy, I'll post the procedure in a sec.

Markus,

Can't find my manual. IIRC, without starting the engine, turn the key on-off-on-off-on. Codes should flash and download via the Check Engine light. If all you see is a 55, then nothing's stored.

Be glad it's not the crank position sensor.

Thanks! Much appreciated!