Rick's Free Auto Repair Advice

Transmission won’t shift

Check engine light on, transmission won’t shift

GM service bulletin #01-07-30-002E for transmission won’t shift

GM has issued a service bulletin ##01-07-30-002E to address a problem where the transmission won’t shift out of 2nd gear or transmission won’t shift out of 3rd gear. You’ll also have a check engine light and one or several of these trouble codes P0740, P0753, P0758, P0785, P0787, P0973, P0976, P1860, P2761, P2764 and P2769. The service bulletin affects the vehicles listed below.

Vehicles affected

2006 and Prior GM Passenger Cars and Light Duty Trucks

2005-2006 HUMMER H2

2006 HUMMER H3

2005-2006 Saab 9-7X; with 4L60-E, 4L65-E, 4L80-E or 4L85-E Automatic Transmission

Cause of transmission won’t shift problem

GM has discovered that the most likely cause of the transmission won’t shift is low voltage to the transmission solenoid power supply circuit. This is most often caused by the improper installation of an aftermarket electronic device like a remote starter or alarm system.

Fix for transmission won’t shift

With the ignition switch in the RUN position, use a voltmeter to test for battery voltage at the circuit fuse in the transmission solenoid power supply circuit. If you don’t see battery voltage at the circuit fuse, refer to a wiring diagram and backtrack to find the source of the voltage drop. The low voltage will cause all of the above listed trouble codes and cause a transmission won’t shift condition because the shift solenoids aren’t receiving the proper voltage.

If battery voltage is present at the fuse, inspect

passlock ignition switch

Ignition Switch

the ignition voltage circuit between the fuse and the transmission for possible opens. If battery voltage is not present at the fuse, test for continuity between the fuse and the ignition switch. If NO continuity is between the fuse and the ignition switch, repair the open in that circuit. If you have continuity between the fuse and the ignition switch, the most likely cause is the ignition switch.

©, 2018 Rick Muscoplat

Posted on by Rick Muscoplat



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