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Fix_It_Man
Fix_It_Man, Repair Supervisor
Category: Transmissions
Satisfied Customers: 17284
Experience:  ASE Master Certified, L! Advanced Level with over 20 years of experience.
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I have a 09 gmc 3500 dually durmax with an allison auto

Customer Question

I have a 09 gmc 3500 dually durmax with an allison auto transmission. The dash gear light flashes and doesn't get out of 2nd gear. You can only use p, r only and it jumps when placed in theses gears truck will not move from 2 ND gear what to do.
Submitted: 1 year ago.
Category: Transmissions
Expert:  Fix_It_Man replied 1 year ago.

Hello, my name is Bobby. Thank you for the question. There are a number of issues that can cause this. I have had ignition switches fail and cause this as well as transmission position sensors and shift solenoids. If the check engine light is coming on also you need to start by having the computer scanned for codes. Most auto parts stores can do this for free. If you bring me any codes I can tell you what is going on.

Customer: replied 1 year ago.
I just scanned the truck and I got three codes p0677, p0706 circuit a, p0711......
Expert:  Fix_It_Man replied 1 year ago.

Those definitely help. Most of the time when you get these codes together it is because of a failure in the wiring harness for the transmission. The wiring harness failure causes the range sensor and the temperature sensor to not read right. I would inspect the harness and connectors on the transmission for damage.