Stubborn GM tranny

This TSB applies to the following vehicles (all equipped with the 6T70/6T75 MH2, LH4, MH6, MY9 automatic transmission). The MIL comes on and the transmission won’t shift through all of the gears. A DTC code P182E is set in the transmission control module.

2008-2009 Buick Enclave

2008-2009 Chevy Equinox and Malibu

2009 Chevy Traverse

2007-2009 GMC Acadia

2007-2009 Pontiac G6

2008-2009 Pontiac Torrent

2007-2009 Saturn Aura and Outlook

2008-2009 Saturn Vue

Make a quick check to see if the engine wiring harness is being chaffed at the front cylinder head machined surface for the valve cover. If the ECM P/N Circuit 1786 is intermittently grounded (when the transmission is in Drive), this code will set and possibly others. If the harness is not chaffed, follow the procedure listed below:

1. Clear the code.
2. Adjust the shift cable per the instruction in the service manual.
3. Check shifter and cable for proper movement with no sticking or escessive effort to move the shifter through all detents. Correct as needed.
4. Connect the scan tool.
5. Start the engine, set the emergency brake and apply the brake pedal. Make 10 sets of shifts from Park to Reverse and Reverse to Park. Shift the shifter through all of the quadrants Park to Lo/M and back to Park, 5 times.
6. Did the code P182E set? If yes, refer to the service manual and complete diagnostics. If no, shift the transmission through each shift quadrant while observing the Mode Switch (IMS) on the scan tool. If switch circuits A/B/C/P change correctly, return the vehicle to the customer.

SCAN TOOL DATA

IMS A/B/C/P Circuit   Switch signal A   Switch signal B   Switch signal C   Switch signal P

 Park                                      Low                      Hi                          Hi                            Low

Reverse                                Low                      Low                       Hi                             Hi

Neutral                                  Hi                          Low                       Hi                            Low

Drive                                      Hi                         Low                        Low                         Hi

Hi = 12V                  Low = 0V