Allison - Automatic Transmission

FastLearn Procedure

Overview

In general, FastLearn is a procedure for Allison 1000 Series transmissions in which a series of tests are run to allow the transmission control module (TCM) to learn individual clutch characteristics. Once the clutch data is learned, FastLearn translates it to the adaptive data cells, which the TCM uses for clutch control during range shifts. FastLearn is used at GM assembly plants, and allows the vehicle to be driven out of the assembly plant in a near-fully-adapted state to minimize any customer shift concerns. The scan tool version of FastLearn is intended to provide the same benefit following transmission repair or replacement at GM Dealerships.

FastLearn must be used when one of the following repairs have been made to the vehicle:

* Transmission replacement or internal service/overhaul
* Valve body repair or replacement, including replacement of the pressure control solenoids
* TCM replacement
* TCM software/calibration update
* Any service in response to a shift quality concern

The scan tool is used to initiate FastLearn by selecting the following commands:

* F3: Special Functions
* F1: Transmission Output Controls
* FastLearn

Note: When performing FastLearn, the following conditions must be met:

* Block the drive wheels.
* Apply the parking brake.
* Apply the service brake during DRIVE and REVERSE.
* 0 percent throttle and engine at idle RPM
* Transmission sump temperature is between 40-100°C (104-212°F) - Ref temp bargraph on screen.
* If equipped, 4WD transfer case in 2WD

Note: If at any time during the procedure, required conditions are not met, FastLearn may abort and the process will need to be started again from the beginning.

Three steps are required to successfully complete the FastLearn procedure:

1. PARK Mode
2. DRIVE Mode
3. REVERSE Mode

PARK Mode

While the transmission is in PARK, with the engine idling at 800 RPM, FastLearn will cycle through a series of tests where the 3rd, 5th and reverse clutch and the 2nd clutch is repeatedly applied to learn their clutch characteristics. During the 3rd, 5th and reverse clutch and 2-6 clutch apply/release procedure, FastLearn is able to characterize the pressure control solenoid 1 (PCS1) and pressure control solenoid 2 (PCS2) pressures corresponding to clutch return springs, and is also able to learn the volumes for the 3rd, 5th and reverse clutch and 2-6 clutch packs. In addition, the low and reverse clutch is repeatedly applied and released in PARK to purge out air for later learning of the clutch volume. The TCC clutch volume and variable main modulation solenoid pressures are also learned. While the transmission is in PARK, the TCM will increase the engine speed to 1,300 RPM to learn these characteristics.

DRIVE Mode

Warning

Block the wheels before selecting DRIVE. While in DRIVE, if the Scan Tool loses communication or becomes disconnected, the vehicle could move forward. Failure to block the wheels could result in personal injury or property damage.

Once all of the PARK test data have converged, the scan tool instructs the driver to select DRIVE. Once DRIVE is selected, the TCM engages the 1-2-3-4 clutch to obtain DRIVE and learn 1-2-3-4 clutch volume. The TCM repeats this test until the volume learned for the 1-2-3-4 clutch has converged. The TCM then engages 4-5-6 clutch until the volume is learned and 4-5-6 clutch has converged.

REVERSE Mode

Warning

Block the wheels before selecting REVERSE. While in REVERSE, if the Scan Tool loses communication or becomes disconnected, the vehicle could move backward. Failure to block the wheels could result in personal injury or property damage.

Next, the scan tool instructs the driver to select REVERSE. Once REVERSE is selected, the TCM engages the low and reverse clutch to obtain REVERSE and to learn the low and reverse clutch volume. The TCM repeats this test until the volume learned for the low and reverse clutch has converged.

Note: All shifts will be left in fast adaptive mode at this point.

After learning the 1-2-3-4 and the low and reverse clutch volume, FastLearn updates the adaptive volume data for all shifts.

Troubleshooting

If FastLearn will not run and the above stated conditions have been met, ensure the following:

* Transmission fluid temperature is between 30-100°C (86-212°F).
* Closed throttle and engine at warm idle RPM
* No active DTCs
* All speed sensors are connected and functioning properly.
* Internal mode switch is functioning properly
* Main pressure is within specification.
* TCC slip speed less than 150 RPM at idle in PARK/NEUTRAL