5.3L L33 (P59) - Is it possible to use an analog A/C request?

[Bayley]

Hello all,

I am trying to retrofit an L33 into a vehicle where the HVAC control head sends a 12V compressor request signal to the PCM.

Does the P59 PCM (Blue & Green) have the ability to accept a 12V compressor request? It is currently setup to support a serial request, and I can't find any pins that would allow the use of a 12V input for request.

I'm hoping that I'm just overlooking something. Would be nice to have compressor control through the PCM without having to add a custom controller.

Thanks,
-B

[Eaglegoat]

The controller is capable of it in at least part #12586243. The OS from the 2004 GTO is the only one I know for sure will work with analog AC. Other OS's may as well.

[Bayley]

Was hoping to not flash a new OS, but it's good to know that option is available as a last report.

Thanks.

[71k3500]

please share your l33 p59 tune. thank you.

[PitchblackC3]

Yes it will, go to:
System----A/C----Type fitted.

Use the drop down to select Analog cycling.

This was added to the truck BLUE/GREEN PCM OSs a couple of years ago.

[Bayley]

Good to hear. I enabled the feature and flashed the update, but didn't get a chance to test the C2-43 pin yet with VCM scanner.

Next question, the system is originally a serial-cycling system:

2005_Silver-AY-doe.jpg

Is my assumption correct that in addition to adding the A/C request (12V ON / 0V OFF) on pin C2-17, I will also need to preserve the A/C pressure sensor signal that is fed into pin C2-14?

EDIT: The circuit above might be for the variable displacement compressor. According to my original ROM dump, my controller had a fixed displacement (cycling) compressor. If that's true, I might only need to ground the low pressure switch on C2-55:

2005_Silver-AY-doe_fixed.jpg