Transmission Fastlearn Procedure - Allison 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 so as 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 solenoid A or the pressure control solenoid B
^ 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

Important: 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 bar graph on screen.
^ If equipped, 4WD transfer case in 2WD

Important: 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.

Four steps are required to successfully complete the FastLearn procedure:

PARK Mode
While the transmission is in PARK, with the engine idling, 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 2nd clutch apply/release procedure, FastLearn is able to characterize the pressure control (PC) solenoid A and PC solenoid B pressures corresponding to clutch return springs, and is also able to learn the volumes for the 3rd, 5th and reverse clutch and 2nd 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.

DRIVE Mode

Caution: While in Drive, if the Scan Tool loses communication, or becomes disconnected, the vehicle may remain in Drive and could move forward if the wheels have not been securely blocked.

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.

REVERSE Mode

Caution: While in Reverse, if the Scan Tool loses communication, or becomes disconnected, the vehicle may remain in Reverse and could move backward if the wheels have not been securely blocked.

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.

Important: 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, with either the 1-2-3-4 or the low and reverse on-coming clutch. This completes the stationary modes of FastLearn.

4-5 Clutch Learn Mode

Important: The technician should verify that transmission shift quality for all types of shifts is acceptable prior to releasing the vehicle to the customer.

Following the REVERSE Mode step, the scan tool exits FastLearn, and the only adaptive cells that remain to be learned are the adaptive volume data for the 4-5 clutch. The vehicle must be driven in order to make at least three 3-4 upshifts on the same ignition cycle and at steady throttle position. This data is learned by the TCM intentionally overfilling the 4-5 clutch. Once this overfill is corrected, the 4-5 clutch volume is learned and all special FastLearn actions are completely disabled.

Troubleshooting
If FastLearn will not run and the above stated conditions have been met, ensure the following:
^ Transmission fluid temperature is between 40-100°C (104-212°F).
^ Closed throttle and engine at warm idle RPM
^ No active DTCs.
^ All speed sensors are connected and functioning properly.
^ Park/Neutral position switch is properly adjusted and functioning.
^ Main pressure is within specification.
^ TCC slip speed less than 100 RPM at idle in PARK/NEUTRAL