Hi.
I have here a GMPP LS3 in '60 Impala which had the EZ-TCU transmission controller. I wasn't happy with the aftermarket transmission controller, so I bought a T42 transmission controller and made a wiring harness to it. I copied the harness layout from GM service manual as it is in 2008 Trailblazer SS which was (to my understanding) with E67 and T42 from factory.
Now I finished with wiring the car. My plan is to have my friend with Tech2 to write the E67 and T42 over with a stock tune from Trailblazer '08. After that I would start normal tuning in hopes the car would no longer have the idle air limitations of GMPP tune and a chance to tune the transmission with HPtuners.
Its not yet written as Trailblazer but I thought I would connect the HPtuners and read if I possibly see the transmission controller there already. I didn't.
The connection failed few times when I started reading the tune (E67 GMPP was recognized) and one time it announced "unknown controllers detected".
Does this mean I'm on the right track or have I messed up something? Is the Tech2 still able to write the tune over even when the present situation shows there is interference with these 2 modules?
To my understanding the only thing affecting the communication is the data communication between ECM (X3 pin 33 to TCM pin 37 / X3 pin 53 to TCM pin 38). This I did by splicing the wires from ECM to TCM and the only other destination for the wires must be the OBD plug. I haven't put a 120 ohm resistor to wires from TCM which would go to BCM if this car had one.