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 bargraph 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
- DRIVE Mode
- REVERSE Mode
- 4-5 Clutch Learn Mode
Principle of Operation
The Allison transmission incorporates control logic that enables the transmission to revert to a limited total hydraulic operation. The hydraulic system provides a Limp Home Mode, allowing the operator to drive the vehicle to a service location. If power is interrupted while the transmission is operating in R, REVERSE, or N, NEUTRAL, the transmission defaults to or continues NEUTRAL operations. The operator may turn off the engine and start the engine again. The shift selector will provide R/N/D, REVERSE/NEUTRAL/DRIVE capability regardless of the range, wherein the failure occurred. In this state, pressure control solenoid A, de-energized, allows the 3rd, 5th and reverse clutch to be applied. If the selector valve is moved to the REVERSE position, main pressure will be routed to the low and reverse clutch, allowing REVERSE operation. If the selector valve is moved to the DRIVE position, main pressure will be routed to the 1-2-3-4 clutch, allowing THIRD range operation.