Hi,
I just joined this forum to get some help. I have been driving 1991 Olds 98 Elite since 2000.
The two radiator fans suddenly stop working a few weeks ago.
Except this problem, everything is fine with this nice car.

From my experience, the fans should spin for several seconds and off when the engine is started. Also, when A/C is on, the two fan should spin.
I monitered both cases but the fans didn't response.

So I bought a GM code reader and checked if there is any code generated.
No code was generated but, interestingly, when the code reder was connected and the key was on but no engine started, the two fans spined.

From the above tests, I think that the fuses, relays, wires, and the fans are fine.
The only thing suspicious is the PCM module.
Is it possible that only one of the functions of PCM can be bad?
Or is there any reason why the fans shows this kind of symptoms?

I really appreciate your help in advance .
movingman

I moved your thread to oldsmobile for better visibility

Is the car overheating?..Turn on your air conditioning and see if one of them turns on..ICR where the fans are set to turn on on your car..

Thank you for your quick response and moving my thread to oldsmobile.

My car doesn't overheat yet and I am watching temp guage carefully these days.
I checked the fans when the AC is ON but they didn't spin.
By the way, what is ICR?

Thanks again,
movingman

Im sorry ICR is me being laazy..It means i cant remember lol

if the fans turn on when you run the diag test, then that rules out alot. your temp sensor is likely bad

I'm going to say temp sensor.

Do you mean the coolant temperature sensor?
I can read the coolant temperature from the driver'* front pannel. Does it mean that the coolant temperature sensor is working fine and gives the temperature value to the display?
I am just double-checking it.

Thank you so much for yor response.
movingman

Even if the coolant temp sensor is bad, when A/C is on, the fans should spin, shouldn't they?

Yes the one should..that temp sensor if faulty is going to tell your ECM a wrong temp and not engange the fan..

Thanks sseidriver97,
I will replace the coolant temperature sensor soon.
I will post the result. Wish me a luck~