Coolant temperature reading issue...
 

Problem is when engine gets warm my coolant temp start jumping all over the place, max.. min .. reading and my engine runs like crap due to coolant correction map being corrupted with these false reading coming from the sensor.

I use to have E8 Haltech and had same issue until E8 failed... it would not read coolant temp anymore even cold... Now I have PS2000 and problem is back, I'm worried ECU might fail completely again.

I have not changed the sensor yet which is located on the back of the termostat housing. I verified the wiring dozen of times... Seems to be ok..

Could it be come interference coming from alternator? Some Grounding issue?
My next step is to replace the sensor ( which I heard never fail) , should I place it somewhere else? Is there a another good location?

I eliminated AST and wired Haltech myself... Did anyone had similar issue?

sounds like there is air next to the sensor, or the sensor is bad.

Coolant is filled all the way to the top... There should be no air, but then again I do not have AST

So it reads normally until the engine comes up to temp? At what temp does it start to read incorrectly? And then once it starts acting up the temp will oscillate between high and low temp?

Yes... Not sure exactly what temp but I'm guessing more than 190... and yes min and max...

Can you email me your map? ludwigmotorsports@insightbb.com

Sent.

Mirko,

Have you tried turning disabling the diagnostic function for the coolant temp sensor? This shouldn't be the issue, but it's an easy try.

Is the harness the same one you used with the old E8? That's the only thing I can think of other than the sensor. The sensor is an unlikely fault, but you never know. I just can't think of a failure mode in any of it that would cause this problem. Very odd.

i've seen two different failures with sensors. the first is the needle jumping around, this happens to the BMW's because the sensor is on top, and the bleeder tank system they have doesn't actually bleed air out, so when it gets hot the sensor is in air/stem/water. it would be a little weird on a rotary, as Mazda put the coolant temp sensor in water.

the second i actually have seen sensors that were broken in a way that it would intermittently be open or short (and occasionally correct, even!) so you'd never know if the car wasn't gong to start because it didn't get any fuel, or it was flooded.

i'd suspect the sensor before the ecu, as the ecu is just reading the signal. you actually should be able to warm the car up and verify with an ohm meter as well

First case might be because I eliminated AST. Local shop told me AST its not necessary. I'm starting to think this might be likely cause.


Second thing you mentioned sounds like what is actually happening. Could this sensor operation damage my first ECU E8? Probably only Haltech guys can answer this. Symptoms were same initially until E8 stopped reading anything coming from the coolant temp sensor, other than that E8 was completely functional.

I will try disabling it.