Replacing the GMPP ECU with a Production E67 for a/c Control.

[TunedIn]

I have an FJ80 that I put a GMPP 6.0 with a 4L80 into. At the time of install I did not realize that the A/C request was not just an input into the ECU. It seams that this is much more complex in terms of a/c request and output to compressor relay. I installed a pressure switch and the RPM Extreme a/c request module only to find out that the GMPP does not support a/c control at all. So the question is, is there a factory calibration to use with a production E67 ECU that would be a direct drop in to work with the GMPP harness and supporting parts. Being that the MAF and the ACC Pedal are what would typically be found on a truck engine I'm not sure what base calibration will work with this GMPP set up. The issue that I am wanting to fix is the drop in idle and occasional stalling when the a/c compressor cycles. Thanks in advance.

[Alvin]

late Trailblazer SS's were E67's. They have a hard wired cruise control too. I've never tried it.

[TunedIn]

late Trailblazer SS's were E67's. They have a hard wired cruise control too. I've never tried it.

So it's been 4 years since this install, I searched through my emails and found a reply to my GMPP parts rep. I forgot that we had discussed this and I actually have a Trailblazer SS ECU here that I ordered back then. I think that wiring wise that was the closest match. The issue from what I remember is that the Trailblazer SS does not have VVT and the 6.0 that I have does. Does anyone know if this is something that can be activated with HP Tuners? I would guess that it's more common to disable this feature then activate it.

[DanN]

So it's been 4 years since this install, I searched through my emails and found a reply to my GMPP parts rep. I forgot that we had discussed this and I actually have a Trailblazer SS ECU here that I ordered back then. I think that wiring wise that was the closest match. The issue from what I remember is that the Trailblazer SS does not have VVT and the 6.0 that I have does. Does anyone know if this is something that can be activated with HP Tuners? I would guess that it's more common to disable this feature then activate it.

So I don't KNOW the answer, but I took a few minutes to poke around.

The TBSS tunes in the repository do have the Variable Camshaft tables in Engine -> Airflow -> Variable Camshaft.

I also found a pinout that shows the CMP controls exist on X2:14 and X2:15 (Intake) and X2:50 and X251 (Exhaust):

14 PK/BK 6395 Camshaft Position (CMP) Actuator Solenoid -- Intake Bank 1 Control
15 TN/BK 6397 Camshaft Position (CMP) Actuator Solenoid -- Intake Bank 2 Control

50 WH/BK 6396 Camshaft Position (CMP) Actuator Solenoid -- Exhaust Bank 1 Control
51 GY/BK 6394 Camshaft Position (CMP) Actuator Solenoid -- Exhaust Bank 2 Control

So from my point of view there is a good possibility it'll do the job.. but I can't say that with any certainty. It could be that the tables exist but aren't enabled for every OS.

[edcmat-l1]

Alvin would know. He has more TBSS experience than anyone active on the board.

[Alvin]

Get rid of the VVT would be my recommendation.. No one trying to make serous power with a GEN 4 uses it.. It just adds complication. They rarely have good VVT control if the thing spins a decent amount of RPM. not worth it.

[verlon]

I have an FJ80 that I put a GMPP 6.0 with a 4L80 into. At the time of install I did not realize that the A/C request was not just an input into the ECU. It seams that this is much more complex in terms of a/c request and output to compressor relay. I installed a pressure switch and the RPM Extreme a/c request module only to find out that the GMPP does not support a/c control at all. So the question is, is there a factory calibration to use with a production E67 ECU that would be a direct drop in to work with the GMPP harness and supporting parts. Being that the MAF and the ACC Pedal are what would typically be found on a truck engine I'm not sure what base calibration will work with this GMPP set up. The issue that I am wanting to fix is the drop in idle and occasional stalling when the a/c compressor cycles. Thanks in advance.

Discrete AC request can be enabled in any E67. I can do it.

P.S. Can you post stock GMPP 6.0 calibration?