I am normally pretty good on car repairs and troubleshooting over the many years but this one is got me stumped. 2003 Monte SS is throwing P0481 "cooling fan control circuit", starts at pending at startup (A/C off), engine cold so not sure even why the PCM is throwing this fault code? Pending eventually triggers the CEL.

Background: Check engine light came on a couple months ago with the code P0481, honestly did not take much time to troubleshoot but when I took a look at the fan motors it appeared that the driver's side fan was making a noise and not spinning at full speed so I decided to swap out the fans That did not solve the problem and I ended up changing 1 of the relays and then all 3. Still had the same issues. Spent more time testing and troubleshooting the circuit and appears everything was working as expected e.g. fans come on low when A/C on, fans come on at temp etc; Jumpered relays and fans came on as expected, 12V at relay etc Next I decided to swap out the coolant temp sensor (not really expecting this was the issue especially since the sensor was not that old), no change.No idea what to look at next, what baffles me is why the PCM is doing anything with the fans at startup? I was under the assumption that the computer did not run any sort of diagnostic testing on the fans at startup?

 

Well, not sure when this happened but found a blown relay fuse. Go figure, wonder if I really needed to change out the fans and relay! I feel like an idiot.

 

Here is a pdf from the service manual on how to troubleshoot your issue. Hope this helps.