Regal L4-2.0L Turbo (2011)
Control Module: Customer Interest
A/T - Delayed Engagement Into Drive And Reverse
TECHNICAL
Bulletin No.: 11-07-30-001
Date: February 23, 2011
Subject: Delayed Transmission Engagement into Drive and Reverse Until Engine RPM is Increased to 1200-1500 RPM, No DTCs Stored In TCM
(Reset Engine Stall Avoidance Drive Pattern)
Models:
2011 Buick Regal
Equipped with Automatic Transmission RPO MDK
Condition
Some customers may comment that when selecting Drive or Reverse, they are experiencing a delayed transmission engagement. The transmission will
engage when the engine RPM is increased to the 1200-1500 RPM range. When the transmission does engage, it may be described as either harsh or have
a "creep" effect. Diagnosis reveals no Diagnostic Trouble Codes (DTC) stored in the transmission control module (TCM) and the transmission fluid is
not distressed and the level is correct. The engine control module (ECM) may or may not have DTCs stored regarding an engine stall or near stall
condition that may have occurred. Possible ECM DTCs: P069E (Fuel Pump Module requested MIL illumination) and P018B or P018D (Fuel Pressure
Sensor) stored in the fuel pump module.
Cause
This condition may be caused by a low fuel volume or pressure condition that creates an erratic/low engine base idle condition. When the TCM
software/transmission calibration detects an engine stall or near stall condition such a low fuel level, with the transmission range switch in the Drive or
Reverse range, the TCM commands the C1 and C3 clutches "OFF" to include the transmission clutch control (TCC).
Current transmission calibrations can perceive this type of stall condition as a TCC related concern "TCC stuck on" and in turn activates or requests the
"Engine Stall Avoidance Mode" feature in the transmission software.
Engine Stall Avoidance is a program feature that requests the transmission to operate in what can be described as a "neutral condition or reduced
engagement condition" in order to confirm if there is an actual concern with the TCC. This reduced engagement event is present in all transmission gear
ranges at low RPM without any DTCs stored until additional diagnostics are run to verify proper TCC operation.
Correction
In order for the TCM to perform a "self-check" to the TCC and confirm it is not the root cause of the engine stall condition, the TCM must "see" or be
able to compare engine RPM and the input speed sensor (ISS) slip speed calculation to confirm that the root cause of the engine stall or near stall
condition was not TCC related.
Use the following procedure to allow the TCM to perform a "self-check."
Engine Stall Avoidance Reset Drive Pattern
1. Confirm that ALL stored DTCs are cleared in all control modules.
2. Confirm that the low fuel level light is "OFF."
3. The ATF temperature needs to be 25°C (77°F) or greater (Note: ATF temp can be verified using GDS).
4. Shift the gear selector level from Park to Drive range and wait for 10 seconds.
5. Lightly accelerate to between 1,200-1,500 RPM and hold this engine RPM for 5-10 seconds.
6. Lightly apply the brakes to come to a complete stop.
7. Repeat steps 4 and 5 above until normal engine/transmission response is verified. (Most generally, the Engine Stall Avoidance feature is
cancelled/cleared in 2 or 3 of the above drive cycles).
Drive the vehicle at operating temperature to the speed the TCC would normally apply. If the TCC applies and operates properly, the TCM will go back
to normal operation and no further repairs would be required. If the TCC does not operate correctly, DTCs would then be stored for further diagnosis
Warranty Information
