Chevy silverado 2500HD vith 8.1 liter engine

[frebo]

Hi,
I have installed a 8.1 liter engine in my 2001 Chevy silverado 2500HD with a 12586242 ECU. I have only two issues with this. The first thing is the activation of the A/C system. and the second thing is the tank level gauge. After I start up the car it goes about 10 sec and the tank gauge goes to empty, and the computer sets DTC code P2068 (pnding). I have tried to reprogram the fuel system with 0 in all the secondary volum fields, but nothing helps. Do anyone know how to program out the secondary tank system from the ECU and is there any way to program the ECU so the A/C will start?

Hope for quick answers.

Regards
Fredrik

[Jon S.]

You are using a 2004 1Mb PCM (Service # 12586242) which will accept Blue and Green connectors.

The 2004 8.1L (and truck LS engines in general) used Serial Data communication with the HVAC Module to activate the A/C Compressor. Your 2001 Silverado would have had a 512 Kb PCM (Blue and Red) connectors, and used a direct input (12 volts) from the HVAC Module to activate the A/C Compressor.

Also, the 2004 PCM is also expecting input from an A/C Pressure Sensor, while your 2001 Silverado will be wired for Low and High A/C Switches (no pressure sensor).

You could try using A/C parameters from a 2001 LS truck tune - if that is how you have wired the A/C system - however, I do not believe that your PCM has the drivers to recognize a 12 volt A/C input.

Both the original 2001 PCM and the 2004 PCM output fuel tank data to the IPC (gauges) using Serial Data. However, the fuel tank / gauge settings are very different between these model years. Also, some HD trucks had single fuel tanks, some had dual fuel tanks, the base programming in the PCM should to match the fuel tank setup in the truck.

Try copying fuel tank / gauge parameters from a 2001 LS truck tune into your 2004 tune.