cooling fans...more problems...great

in my 97 grand prix gtp my cooling fans stopped turning on. it was diagnosed as the coolant senser which ended up reading -35 degrees constantly. i replaced the sensor with a brand new one... and my fans still do not turn on. does anyone have any idea what could be the problem? band wiring connection to the fans? pcm connection?

What is the engine temperature reading on the gauge? Disconnect the ECT sensor (engine coolant temperature) and see if both cooling fans turn on in about 5 seconds. Be sure to disconnect it with ignition to off and then start it up.

was the SES light tripped due to the bad sensor? If so, the code needs to be cleared before the PCM will recognize a new sensor was installed.

i currently have the sensor unplugged so that the fans stay on constantly to avoid any chance of over heating. id rather have them always on than always off. and i have had the codes cleared and the SES light came back on.

''i currently have the sensor unplugged so that the fans stay on constantly to avoid any chance of over heating''.it's not a good idea to run car this way

But when the ECT sensor is plugged in what does the temperature gauge read and does it actually overheat? When the weather cools down and the A/C is not needed then the cooling fans will not come on in low speed until around 220 degrees. Around 230 degrees to high speed.

If you have the code (DTC) post it.

it DOES read when it is plugged in and it gets in excess of 230. i shut the motor off when i noticed that. when we were trying to fix it it was near redline while we werent watching. obviously while im cruising it cools down a bit but the fans themselves never go on unless its unplugged

check the fan control relays in the underhood relay center first before tracing wiring.

The fans run with the ECT sensor disconnected (fail safe mode) so the cooling fans relays are good. On the fans not turning on in normal driving conditions sounds more like a control issue related to the PCM module. Also, this engine is overheating meaning there are other issues in the cooling system.

well it only gets that hot when its idling and the fans arent on.

What part of the country are you in? If your cooling system is good and there are no other issues engine related you normally don't need the cooling fans this time of year. I can sit at at a long idle and the temperature never exceeds 210 degrees and most of the time the fans are not on. What does it do with the A/C on? Do the fans turn on?

When was the last cooling system service meaning when was the radiator and the rest of the cooling system flushed and new anti-freeze put in? How old is the thermostat?

Also did you not say you had a DTC and SES/CEL light. Posting it would help.

i live in northern ohio. on hotter days like 80 or more or whatever at idle it gets hot. theres no air flow to cool off the coolant. my A/C doesnt work... the resevior or whatever cracked and the pump burnt out... as for the SES light its a P0171 code for lean fuel mixture or whatever. as far as ive been told its unrelated to the fan issue.

a lean condition could cause a motor to overheat.

What are your Long term fuel trim readings?

One more question (maybe for a moderator), do these cars have two seed fans? is there a seperate relay for low and one for high?

Is it possible the fans aren't coming on in low speed and cuasing the car to overheat?

One more question (maybe for a moderator), do these cars have two seed fans? is there a seperate relay for low and one for high?

Is it possible the fans aren't coming on in low speed and causing the car to overheat?

Something is not right Tim. Until the coolant temperature gets to around 220 degrees the cooling fans should not even be running in low speed of course with A/C off. It has nothing to do with air flow. It is the efficiency of the cooling system which means having no other issues. I still think there is another issue causing the temperature creep up. Having a non-op A/C doesn't help either. I had to check another Grand Prix GTP (stock) since I have the Intense PCM with the modified fan turn on points in mine and with A/C off, engine warmed up, and idling at least 10 minutes his temperature never exceeded 200 degrees on the gauge. The outside temperature at the time was 81 degrees F. Note: The cooling fans never turned on.

Now to answer your question there are three cooling fan relays, one for low and one for high and the other is used to turn the fans on in different conditions.

It sounds like he would be a good candidate for a re-programmed PCM module where the fans turn on at 180 degrees or one of those switch kits to manually turn the fans on.

i dont know the long or short term fuel trim right now but i will get that info on saturday. is it possible that the PCM is causing the fan problem AND the lean fuel condition? if my pcm just went bad some how.

Thanks for the info Bob!

And yeah, anything is possible with the PCM, but check the working and grounds for the sensor first. A flashed pcm will have the same problem as the original with the cooling system if its a wiring problem to the sensor or sensor itself.

How long has it been since the t-stat was changed?

couldnt tell ya. but the mechanic looked at it when i changed the coolant sensor and said it was fine. unless he was wrong. i have a new one that i was about to return...should i install it?

..... i have a new one that i was about to return...should i install it?


Why not? Its a cheap part and if yours is still the original, its time for replacement. Might just cure your problem.