I've got a '97 Camaro PCM in my truck that is handling the engine and transmission control. I've been banging my head over a little issue that I can't tell if it is intentional or a fault. When the shifter is in the D4 position, I can get the truck to engage the torque converter lock-up in 2nd (for testing purposes) and 4th gear. 3rd gear lockup never occurs despite the vehicle speed set points being OK. If I drop the shifter into D3, the transmission then begins to lock-up and 2nd and 3rd as you would expect.

Checking in the datalogger shows that the PCM is indeed not commanding a 3rd gear TCC lock when the shifter is in D4. All other inputs (brake, shift position, transmission temp, current gear, etc) look OK. I talked to the tech support at Jet (as I am using the Dynamic Spectrum Tuner) and they confirmed they couldn't see anything wrong in my tune, but otherwise provided no help.

Anyone work with one of these PCMs before and know if this is normal behavior or not? In my case it kind of sucks as I'd like to treat the performance shift option as a tow/haul feature to change shift points and disable 4th gear, but as of right now I'll have to drop the shifter to D3 to keep it out of overdrive while retaining a torque converter lock. This doesn't stop the truck from working, but I'm at the stage where I'm starting to nit-pick functions. ;)