Transaxle Control Module Adaptive Control (97-40-030)

TRANSAXLE CONTROL MODULE ADAPTIVE CONTROL

TECHNICAL SERVICE BULLETIN

DESCRIPTION

Adaptive control is a software feature built into Hyundai transaxle control modules (TCM) to compensate for:

1. Component parameter drift over time, and
2. Mechanical tolerance changes which may occur during the life of a transaxle due to normal wear

Adaptive control was applied to all TCMs beginning with the 1991 model year. With adaptive control, the TCM compensates for transaxle clutch clearances that are at the high or low end of the specification. The TCM measures the time required to complete the shift from N-R and N-D and compares to a target time of approximately 0.5 - 0.6 seconds. If the shift time is more or less than the target time, the TCM adjusts the pressure control solenoid valve (PCSV) duty cycle during the shift to meet the target time. In a similar manner, the TCM adjusts PCSV duty cycle for the upshifts and downshifts between 1-2, 2-3 and 3-4 gears.

SERVICE PROCEDURE

Whenever a TCM is installed in a vehicle, the TCM must begin adaptive "learning."

• If a TCM is disconnected from battery power, the TCM must restore adaptive "learning" after reconnection to battery power. (DO NOT return the vehicle to the customer until adaptive learning is completed.)
• If a transaxle was replaced, the TCM must "relearn" adaptive control parameters to accommodate the new transaxle. Do not conclude that the transaxle has an internal concern until adaptive learning is completed.

The TCM will complete adaptive "learning" during normal driving. Depending on the production variations within the transaxle, up to ten upshifts and downshifts between 1-2, 2-3 and 3-4 at varying throttle inputs may be required. Up to ten gear engagements from Neutral to Reverse and Neutral to Drive may also be required.