My 09 335 with a 6 speed Allison transmission won’t shift into gear. Parked the truck and it worked fine, a few days later went to drive it, pressed the brake pedal, pushed the drive button and nothing. When you turn the engine off and with the key on I can push the key pad and it displays the gear selected, then start the engine and nothing. My truck only has 40,000 miles on it. I have checked the harnesses for rodent damage but doesn’t appear to be any. I checked all the fuses. Maybe I should swap relays? Any ideas would be appreciated.
I've ran into this a lot with the fleet I take care of. It's usually the park brake /switch sensor. The TCM has to know the parking brake circuit is aired up before it will allow it to go into gear. You can use the shift console to check the TCM codes. Pete and KW hide the sensor deep inside the dash near the fire wall. Moisture in the air system during cold weather can cause the switch to act this way, too.
Same on just about any later AMT transmissions, has to have a minimum 100 psi .
I found these pressure switches to the left of the steering column. The one on the right with the white wires is labeled brake. Does one of these look like the possible problem and if so is there a way to test it or should I just replace it? Thanks
Would suspect the Yellow Banded beast. Would need a wiring diagram to confirm.
I suspect that DMiller is correct. Once you purchase the replacement switch, you will know for sure. Fairly inexpensive, so I would test it by replacing it with a known good one.