99 Grand Prix, Code P0480

[Toney 24]

I have a 99 Grand Prix GT with a 3800.
I am getting a P0480 code, I have replaced the temp sending unit and the relay. The fuse is good. I clear the code and it comes back, sometimes when the engine is cold.
I need help please!

[GTP Dad]

Welcome to AF!!

Did you use teflon tape on the threads? If so remove the sending unit and remove the teflon tape. Use a conductive thread sealant and the problem should go away. The unit relies on the threads for ground and if the teflon tape interferes with that the unit may not work properly and set a code.

[maxwedge]

Welcome to AF. A bidirectional scanner can command the fan on and confirm the circuitry and fan itself, sounds like a wiring or continuity problem, look at the harnesses carefully.

[Toney 24]

Originally Posted by GTP Dad

Welcome to AF!!

Did you use teflon tape on the threads? If so remove the sending unit and remove the teflon tape. Use a conductive thread sealant and the problem should go away. The unit relies on the threads for ground and if the teflon tape interferes with that the unit may not work properly and set a code.

The sender has 2 wires, one of those goes to a ground on the PCM.

[Toney 24]

Originally Posted by maxwedge

Welcome to AF. A bidirectional scanner can command the fan on and confirm the circuitry and fan itself, sounds like a wiring or continuity problem, look at the harnesses carefully.

I crossed pins 30 and 85 on the relay and the fan came on, this tells me that the circuit is good. Sometimes the Service Engine Light comes on even when the engine is cold. I think the problem is in the PCM, what do you think?

[maxwedge]

Check this link, but again a bi directional scanner will eliminate guess work. http://service.gm.com/gmspo/mode6/pd...CGHWE.pdfguess