0411 ECU Controlling e-fans

[BBPanel]

No, not yet - I have a scanning tool - will that tell me?

[LRT]

Depends on the scanner. EFILive's Scan Tool will display the OS.

[BBPanel]

Its an Actron - guess I can try and see - will probably be tomorrow though

[BBPanel]

Could not find OS but I found VIN and it translates to a 2002 GMC Sierra 2500HD 2WD.

I take that back - there is a CAL ID - 12212156

[LRT]

The good news is, whoever programmed the PCM for you, used the best OS available for the 512 Kb PCM.

Without tuning software, you can't confirm the fan parameters in the tune, but you can still check a few things.

Using your scanner, check what ECT (engine coolant temperature) and A/C Pressure the PCM is registering when the fan(s) come on.

You mentioned having manually grounded each fan relay individually to confirm the wiring. Try disconnecting the High Fan (Fan 2) relay from the PCM, to determine if the Low Fan (Fan 1) subsequently activates correctly. The High Fan (Fan 2) output pin in the PCM would have originally been configured for A/C recirculation - perhaps this was not changed during the initial tune.

[BBPanel]

Well, the PCM has not been tuned/programmed yet - it is just a take-out - maybe I just got lucky. I will check out the ECT and a/c press tomorrow.
No I didn't ground the relays individually, I grounded the hi and lo signal wires attached to the relay circuit with them disconnected from the PCM - to verify the relay circuit is working correctly and it is.

[LRT]

Generally people disable VATS in the PCM with tuning software to get the engine to run - not sure how yours is actually running.

If this is a stock PCM, then disconnect the High Fan (Fan 2) wire from the PCM - it will be still functioning as A/C Recirculation.