I have a Malibu LS 2004 3.5L. I have to always work the AC in order to maintain an appropiate enginne temperature driving in city. . With the car parked and the enginne working at idle the fan rad works fine but sometimes it´s having a delay to work. Driving in highway there is no any problem.
May somebody help me?
Best regards.

 

The PCM runs the cooling fans based on what the ECT sensor says the engine coolant temperature is. Both cooling fans work in tandem, albeit at two different configurations, in series (low speed operation) and in parallel (high speed). At 106°C (223°F) the fans should engage in the low speed operation. Then, at 110°C (230°F) the high speed operation should kick in. With A/C compressor on, the PCM will command the fans on based also on the refrigerant pressure. There's a bunch of steps to diagnose the problem like yours but it's not easy if you don't have a proper scan tool.

 

OK, thanks very much.
Now I have a better idea of the issue.
some time ago, I had some problems with the battery charge and the electric mechanic told me that there was a problem with the modulus because of humidity entrance. he eliminates the security system from the modulus (anti-theft system (my english is not good enough)) and the charging problem was solved.
I think there is a relationship betwen the PCM you told me and the modulus the mechanic told me (Probably is the same, isn´t it).

Do you think I can diagnose the problem with the OBDLink interface of Palmer Performance? I have this one but I have not used yet because I need some instruction about it. I´ll have to learn.

Best regards.

 

You're quite welcome. Any software or hardware scan tool will probably do. Start with sanity-checking the coolant temperature to make sure it isn't registering too low.