Fast Learn Procedure
Fast Learn ProcedureOverview
In general, Fast Learn 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, Fast Learn translates it to the adaptive data cells, which the TCM uses for clutch control during range shifts. Fast Learn 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 Fast Learn is intended to provide the same benefit following transmission repair or replacement at GM Dealerships.
Fast Learn 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 A or B solenoids
^ TCM replacement
^ TCM software/calibration update
^ Any service in response to a shift quality concern
The scan tool is used to initiate Fast Learn by selecting the following commands:
^ F3: Special Functions
^ F1: Transmission Output Controls
^ Fast Learn
Important: When performing Fast Learn, 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 barograph on screen.
^ If equipped, 4WD transfer case in 2WD
Important:
If at any time during the procedure, required conditions are not met, Fast Learn may abort and the process will need to be started again from the beginning.
Four steps are required to successfully complete the Fast Learn procedure:
1. PARK Mode
2. DRIVE Mode
3. REVERSE Mode
4. C2 Learn Mode
PARK Mode
While the transmission is in PARK with the engine idling, Fast Learn will cycle through a series of tests where C3 and C4 clutches are repeatedly applied to learn their clutch characteristics. During the C3 and C4 clutch apply/release procedure, Fast Learn is able to characterize the A and B solenoid pressures corresponding to clutch return springs, and is also able to learn the volumes for C3 and C4 clutch packs. In addition, the C5 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 C1 clutch to obtain DRIVE and learn C1 clutch volume. The TCM repeats this test until the volume learned for C1 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 C5 clutch to obtain REVERSE and learn C5 clutch volume. The TCM repeats this test until the volume learned for C5 clutch has converged.
Important:
All shifts will be left in fast adaptive mode at this point.
After learning C1 and C5 clutch volume, Fast Learn updates the adaptive volume data for all shifts, with either C1 or C5 on-coming clutch. This completes the stationary modes of Fast Learn.
C2 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 Fast Learn, and the only adaptive cells that remain to be learned are the adaptive volume data for C2 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 C2 clutch. Once this overfill is corrected, C2 clutch volume is learned and all special Fast Learn actions are completely disabled.
Troubleshooting
If Fast Learn 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.
^ NSBU switch is properly adjusted and functioning.
^ Main pressure is within specification.
^ TCC slip speed less than 100 RPM at idle in PARK/NEUTRAL