Transmission Control Systems: Description and Operation

RE4F03V



A/T CONTROL UNIT FUNCTION
The function of the A/T control unit is to:
^ Receive input signals sent from various switches and sensors.
^ Determine required line pressure, shifting point, lock-up operation, and engine brake operation.
^ Send required output signals to the respective solenoids.




INPUT/OUTPUT SIGNAL OF A/T CONTROL UNIT

FAIL-SAFE
The A/T control unit has an electronic Fail-Safe (limp home mode). This allows the vehicle to be driven even if a major electrical input/output device circuit is damaged.
Under Fail-Safe, the vehicle always runs in third gear with shift lever position of 1, 2 or D. Customer may say "Sluggish, poor acceleration".
When ignition key is turned "ON" under Fail-Safe operation, OD OFF indicator lamp blinks for about 8 seconds.
Fail-Safe may occur without electrical circuit damage if the vehicle is driven under extreme conditions (such as excessive wheel spin followed by sudden braking). To recover normal shift pattern, turn key OFF for 3 seconds, then ON.
The OD OFF indicator lamp blinks for about 8 seconds, but will appear only once. This indicates the Fail-safe (limp home mode) is cleared. The customer may resume normal driving.
Always follow the "WORK FLOW".
The SELF-DIAGNOSIS results will be as follows:
^ The first SELF-DIAGNOSIS will indicate damage to the vehicle speed sensor or the revolution sensor During the next SELF-DIAGNOSIS, performed after checking the sensors, no damage will be indicated.

ATF COOLER SERVICE
Flush or replace Automatic Transmission Fluid (ATF) cooler if excessive foreign material is found in oil pan or clogging strainer.
GA16DE/SR20DE engine (RL4F03A/RE4F03V)...fin type cooler
^ Replace radiator assembly with a new one. Flush cooler lines using cleaning solvent and compressed air.

OBD-II SELF-DIAGNOSIS
^ A/T self-diagnosis is performed by the A/T control unit in combination with the Engine Control Module (ECM). The results can be read through the blinking pattern of the OD OFF indicator or the Malfunction Indicator Lamp (MIL).
^ The self-diagnostic results indicated by the MIL are automatically stored in both the ECM and A/T control unit memories.
Always perform the procedure "HOW TO ERASE DTC" to complete the repair and avoid unnecessary blinking of the MIL.
^ The following self-diagnostic items can be detected using ECM self-diagnostic results mode only when the OD OFF indicator lamp does not indicate any malfunctions.
^ Improper shifting to 1st, 2nd, 3rd, or 4th gear position
^ Improper torque converter clutch operation.