Test Battery cooling fan

try putting a tissue on the intake grille

 

Probably works like the one in the Gen 3 liftback (this is from the liftback repair manual).



You give it +12 V on IG0 and ground on GND0, you send it a signal for "I'd like you to run this fast please" on SI0, and it sends you back "ok, I'm running this fast" on VM0. (For some reason, they send the "please run this fast" signal from the power management control ECU, but the "ok, I'm running this fast" signal goes to the battery smart unit, who translates it into "ok, he's running this fast" messages and sends those over the comm bus back to the power management control ECU. Rube Goldberg is alive and well....)

I am not finding details in the manual about the exact nature of that SI0 signal, whether it is a pulse train (like the way the water pump works) or a voltage range.

 

i hope it isn't rodente have you owned the car since new?

 

It is always best to look in the repair manual and wiring diagram for your model (more info), but to the best of my knowledge what you've got in the c is pretty close to what is used in the liftback, as shown in the circuit diagram a few posts above.

Is the fuse you are replacing the "BATT FAN" fuse in a unit that looks like this, in the underhood fuse box?



If so, the relay you're looking for (that's shown in the diagram above) is that unit. It's called an integration relay, which as you can see also has the relays and fuses for EFI MAIN and IG2.

You might have better options for troubleshooting the problem than just guessing about the relay. You've probably got about 16 pages of troubleshooting advice in your repair manual in the section for the P0A84 code; at least that's about what I'm seeing in the liftback manual, and I'd bet yours is similar.

 

I just didn't look enough; it's Waveform 5 at the start of the Power Management Control ECU diagnostics section.

Looks (by eyeballing that diagram) to be a roughly 400 Hz square wave, and probably the % of duty it is pulled down gives the speed you want (my guess, anyway, because grounding it apparently works on the bench as a quick way to see if the fan runs).