Diagnoses for Service Fast Learn Adapts Fails, No Forward or No Reverse - keywords 6l50 6l80 6l90 6t70 6t75 adapts code dtc fast forward l4 l5 l50 l6 l7 l80 l90 learn mh2 mh4 mh6 my9 myb myc myd no

This PI was superceded to add the CTS. Please discard PIP4219B.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

When running the Service Fast Learn Adapts procedure with the Tech·2®, the procedure may fail and the following may result:

If the Service Fast Learn Adapts is run and fails, do the following steps:

1. Place the transmission in PARK.
2. Exit the SFL procedure on the Tech·2®.
3. Turn the ignition key to the OFF position.
4. Open the vehicle door with the ignition key still in the OFF position. Wait at least 30 seconds before starting the vehicle or using the Tech·2®.
5. Check and clear any DTCs that may have been set.
6. Adapts will not be overwritten or updated if the Service Fast Learn Adapts fails. There is no impact to the TCM.

These conditions may also be caused by the TCM not properly completing its shutdown. To prevent these conditions from occurring, the following shutdown procedure must be performed after running Service Fast Learn Adapts.

1. Place the transmission in PARK.
2. Exit the Service Fast Learn Adapts procedure on the Tech·2®.
3. Turn the ignition key to the OFF position.
4. Open the vehicle door with the ignition key still in the OFF position and wait at least 30 seconds before starting the vehicle or using the Tech·2®.

The following drive procedure can be successfully used as a substitute.

A drive cycle requires five light throttle accelerations to 40km/h (25mph) and five light throttle accelerations to 64km/h (40mph).

1. From a complete stop, lightly accelerate at a relatively constant throttle pedal position up to 40km/h (25mph) or 64km/h (40mph).
2. Brake the vehicle to a complete stop.
3. Repeat five times to 40km/h (25mph) and five times to 64km/h (40mph). Maneuvers can be performed in any combination.

If the garage shifts (Park to Reverse, Park to Drive, Reverse to Drive, Drive to Reverse) feel like they are delayed, garage shifts adapts can also be performed. All garage shifts should be performed with the vehicle stopped, foot on the brake and engine at idle.

1. Shift the transmission from Reverse to Drive leaving the shift lever in Drive for three seconds. After three seconds, shift back to Reverse, leaving the shift lever in Reverse for three seconds. Perform the procedure 10 times (R-D-R-D-R-D...). The transitions need to be directly to Drive and Reverse, without stopping in Neutral.
2. Shift the transmission from Neutral to Drive leaving the shift lever in Drive for three seconds. After three seconds, shift back to Neutral, leaving the shift lever in Neutral for three seconds. Perform the procedure 10 times (N-D-N-D-N-D...).
3. Shift the transmission from Neutral to Reverse leaving the shift lever in Reverse for three seconds. After three seconds, shift back to Neutral, leaving the shift lever in Neutral for three seconds. Perform the procedure 10 times (R-N-R-N-R-N...).

At the end of these maneuvers, the vehicle may still experience some minor driveability issues, but should learn improved shifting performance over the next several key cycles and driving time. Coach the customer about the transmission's ability to self-correct shifting issues or concerns. The transmission adapts are always functional and operate at transmission oil temperatures above 40°C (104°F).

The drive procedure is required when:

The drive procedure is NOT required when the transmission is replaced. Replacement transmission assemblies already have the adapts set by the transmission plant.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.