With the ignition in the ON position, the tramsmission control module supplies voltage to the automatic transmission park interlock relay. The relay coil is permanently grounded. When the relay is energized, the brake applied voltage signal continues to the automatic transmission park lock solenoid. The automatic transmission shift lock control solenoid is also permanently grounded. This energizes the automatic transmission shift lock control solenoid allows the transmission shift lever to be moved from the PARK position. When the brake pedal is released, the contacts in the stop lamp switch open, de-energizing the automatic transmission shift lock control solenoid. This locks the shift lever in the PARK position.

If the automatic transmission shift lock control circuit is open, the A/T shift lock solenoid will be inoperative. The vehicle will not shift out of PARK with or without depressing the brake pedal.

Schematic Reference

Shift Lock Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Transmission Shift Lock Control Description and Operation

Electrical Information Reference

Ignition ON, the gear shift lever should be locked in the PARK position. When the brake pedal is depressed, the gear shift lever can be moved to any gear selection.

1. Ignition OFF, disconnect the harness connector at the automatic transmission park interlock relay.
2. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal 2 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the relay ignition supply voltage circuit terminal 1 and ground.

⇒	If the test lamp does not illuminate, test for an open or short to ground in the ignition supply voltage circuit. If the circuit tests normal, test or replace the relay.

4. Ignition ON, depress brake pedal, verify that a test lamp illuminates between the relay signal circuit terminal 5 and ground.

⇒

If the test lamp does not illuminate, test for an open or short to ground in the relay signal circuit or a short to ground in the automatic transmission shift lock control solenoid control circuit. If the circuits test normal, perform the automatic transmission shift lock solenoid component test. If the solenoid tests normal, replace the stoplamp switch.

5. Ignition OFF, disconnect the harness connector at the automatic transmission shift lock control solenoid.
6. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal 6 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Ignition OFF, verify that a test lamp does not illuminate between the solenoid control circuit terminal 8 and ground.

⇒	If the test lamp illuminates, test the automatic transmission park interlock relay signal circuit and the automatic transmission shift lock control solenoid control circuits for a short to B+.

8. Ignition OFF, depress the brake pedal, verify that a test lamp does not illuminate between the control circuit terminal 8 and ground.

⇒	If the test lamp illuminates, test for a short to B+ in the relay ignition supply voltage circuit. If the circuit tests normal, test or replace the automatic transmission park interlock relay.

9. Ignition ON, brake pedal not depressed, verify that a test lamp does not illuminate between the control circuit terminal 8 and ground.

⇒	If the test lamp illuminates, test or replace the stoplamp switch.

10. Test or replace the automatic transmission shift lock control solenoid.

1. Install a 10 A fused jumper wire from 12 volts to the automatic transmission shift lock solenoid control circuit terminal 8. Momentarily connect a jumper wire from ground to terminal 6.
2. Listen for the solenoid to turn ON and OFF.

⇒	If the function does not perform as specified, replace the automatic transmission shift lock solenoid.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.