This bulletin applies to 2015 GMC Yukon and Sierra vehicles. Customers may comment about firm 1-2 upshifts, firm 3-1 downshifts, engine rpm flare on tip-in and the MIL on. The technician may find DTCs P0606, P16F3 or P2818 set as current or history.

A revised software calibration has been released to address these concerns. Update the TCM using the Service Programming System (SPS) with the latest calibration available on TIS2WEB. Refer to the K71 Transmission Control Module Programming and Setup in the service manual.

Verify that battery voltage is more than 12 volts but less than 16 volts before reprogramming. Connect the approved Midtronics PSC 550 battery maintainer to the vehicle or the GR8 in the power supply mode.

1. With ignition ON, clear any DTCs.

2. Turn the ignition OFF, and turn off all vehicle systems. It may take up to 2 minutes for all vehicle control modules to power down. Note: If the transmission fluid temperature is not between 167 degrees Fahrenheit and 185 degrees F, the scan tool will not allow you to perform the service fast learn procedure.

3. With the engine running, place the transmission in the drive position and apply the brakes. Perform the service fast learn procedure with a scan tool. Follow the instructions on the scan tool.

4. Turn the ignition OFF for 2 minutes.

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