cshaw

I am part way through doing a LS1 engine conversion to an 81 Corvette and used a 2004 Holden VY Commodore for the donor. All the Holdens controlled the low speed relay from an output on the Body Control Module (BCM) and the high speed relay was run off the PCM.

My questions are:
- Does anyone know why Holden ran the low speed setting like this?
- Secondly can I run the low speed from the PCM and just use a tuning program to activate the low speed relay output on the PCM? (I dont have the BCM and it would simplify things to wire the low speed relay to the PCM)

arthropraxis

I used a LS1 from a 2004 GTO that has the same setup. BCM controlling one of the fans. I read that other people did have a pin turned on for the fan. I don't have which pin it was with me. I think it was the pin that was on the 2001 F-body PCM for the low speed fan. If you are going to run A/C you might as well just get a F-body PCM because the A/C request signal comes from the BCM.

cshaw

I am not going to spend money buying a BCM if I can just turn on a pin in some tuning software. I am not running AC as well.

Why is the low speed run off the BCM? I can't see the logic for this

vltrb-0

ever get a resolution for this? i'm having the exact same issue and can't activate fan #2 (thinking it might be a logic issue with fan #1 bcm deleted)

cshaw

I just put a second pin into the PCM connector where the fan is normally wired in most other LS1 applications. Then I used HP tuners to make sure it was set correctly. No problems getting it working.

vltrb-0

legend so that would be the pin 42 everyone is talking about?

i might test it with continuity and force fan 1 on with the scanner

do you know if there is any reason why just fan #2 can't be used seems stupid you have to be forced to manually pin the pcm when all im after is a ground trigger by temperature (pin 33 for me has been setup and tested i just couldn't activate it)

cshaw

It's been a long time since I did the wiring so I can't remember exactly which pin to use. If you are only using one fan then you should be able to get the wire that is already in the PCM to run the single fan. Just use a scanning program to force it on and off to test it.

vltrb-0

well that's my problem at the moment i have it set up on the existing pin and i have tested it by forcing it on in the scanner but i can't for the life of me get it to activate via the cooling temp triggers

i was thinking it may be a software logic issue, i have some logs on hp tuner if your interested in seeing it in a bit more detail

rain man

Thread back from the dead, but i found this thread with a search, had an LS conversion in a car that was running a stand alone fan controller and wanted to use the PCM to work the fans.

Got pin 33 to work with HP tuners... the following DTCs were set to no error reported, not sure if its necessary or not, but thats what it was set at.

P1160 Cooling fan control circuits
P0489 Fan 1 control circuit

Make sure Fan Type under fans is set to 2 fans.

Someone had selected 'No Fans' in the tune and the scanners fan on/off wouldnt override it until this was set back to 2 fans.... took a while to work that one out.

Putting this out there for anyone else who comes across this, no BCM on this car, just a PCM (holden) with VATS off.

The holden tech info says high speed fans (PCM #33 earth) wont work unless BCM has the low speed on first, but with low speed fans set to no error report, high speed works.