Serial/Data port wiring

[Holden202T]

if its not in limp home mode then the only way the fan would come on is if the coolant sensor gives the pcm a signal that's above the fan on point in the tune!

the fact its not on with the ignition on tells me its not limp home mode (its on as soon as you put the ignition on)

[yoda69]

If using a VT or later PCM/ECU without a BCM fans will come on as is it expecting a reply from the BCM on the fan status.
Same thing happens when you're logging and tell all the modules to shut up.

[Skullator]

Thanks for that Yoda , i had a feeling that was the case
Vl400 has a solution for me
Cheers
Mike