Shift Solenoid: Description and Operation

SHIFT SOLENOID A/B (No.1/No.2)

SYSTEM DESCRIPTION
The ECM uses signals from the NCO revolution sensor and vehicle speed sensor to detect the actual gear position (1st, 2nd, 3rd or 4th gear).
Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical trouble of the shift solenoid valves, valve body or automatic transmission (clutch, brake or gear etc.).





CIRCUIT DESCRIPTION
Shifting from 1st to 4th is done in combination with ON and OFF of the shift solenoid valves No.1 and No.2 controlled by ECM. If an open or short circuit occurs in either of the shift solenoid valves, the ECM controls the remaining normal shift solenoid valve to allow the vehicle to be operated smoothly (Fail safe function).

Fail Safe Function
If either of the shift solenoid valve circuits develops an open or a short, the ECM turns the other shift solenoid ON and OFF to shift to the gear positions shown in the table above. The ECM also turns the shift solenoid valve SL OFF at the same time. If both solenoids are malfunctioning, hydraulic control cannot be done electronically and must be done manually.
Manual shifting as shown in the above table must be done (In the case of a short circuit, the ECM stops sending current to the short circuited solenoid).


SHIFT SOLENOID E (SL)

SYSTEM DESCRIPTION
The ECM uses the signals from the NCO revolution sensor and crankshaft position sensor to monitor the engagement condition of the lock-up clutch Then the ECM compares the engagement condition of the lock-up clutch with the lock-up schedule in the ECM memory to detect mechanical trouble of the shift solenoid valve SLU, valve body, torque converter clutch or automatic transmission (clutch, brake or gear etc.)