E38 valid AC pressure signal.

[VEGASROBBI]

The OS is 12639835 and the Cal. is 12633238. 2011 GM 6.2 L94 truck.

I'm running the cooling fans for ECT through the E38 which works fine. I would like to control AC condenser pressure through the ECM, I have done this in the past with early E38's and it worked fine.

Problem is I get no AC pressure signal on live data, voltage shows 0 and psi is 0 so fans do not come on. I am running the lo ref-signal-5V right into the ECM in the proper cavities from the stock pressure transducer. I do have voltage on the signal wire, it reads properly according to AC pressure, just no valid data is getting into the ECM for fan control.

Not sure if something is disabled or a segment is missing? I am using PWM Electric for fan output; however I tried the other fan outputs with the same result, no AC pressure signal. I tried a different E38 with an LC9 calibration and same thing, no AC pressure into ECM.

Any help is appreciated.

[rpmextreme]

You need a valid "ac request" message sent on the canbus to tell the ECU that ac is requested. It should still read the ac pressure with a scan tool without the message though, just tested it on a 2013 5.3 calibration.

[VEGASROBBI]

You need a valid "ac request" message sent on the canbus to tell the ECU that ac is requested. It should still read the ac pressure with a scan tool without the message though, just tested it on a 2013 5.3 calibration.

What OS and ECM are you running?

[rpmextreme]

E38 12639835
Just running E38 X1-12 to the Jeep AC pressure transducer signal wire give me a correct pressure reading on the GM side with a scan tool. But you will need a canbus solution to send the AC request message to the ECM before it will run the fans or turn on a compressor. It may run the fan without the message, never really tried it. But i do know you need the can message for Ac compressor and idle control.

[VEGASROBBI]

I'm running a 238 E38 with that OS in a 6.2, no luck. Do you have a vin?

[rpmextreme]

I'm running a 238 E38 with a 5.3 LC9 vin currently and it works.

[bignick]

I figured out the solution and you don?t have to buy a $300 canbus module.

https://forum.hptuners.com/showthrea...251#post699251