GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Shift Lock Control Schematics

Connector End View Reference: Shift Lock Control Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems

DEFINITION: Transmission shift lever does not lock in the PARK position with the ignition ON and the brake pedal not pressed.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Apply the parking brake and block the wheels.
  2. Turn ON the ignition, with the engine OFF.
  3. Attempt to move the shift lever out of the PARK position without pressing the brake pedal.

Does the shift lever move out of the PARK position?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

  1. Disconnect the automatic transmission (A/T) shift lock control switch.
  2. Install a scan tool.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the park neutral position switch park signal circuit of the A/T shift lock control switch with a test lamp that is connected to a good ground.
  5. With a scan tool, command the Brake to Shift Output ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 4

Go to Step 6

4

  1. Turn OFF the ignition.
  2. Reconnect the A/T shift lock control switch.
  3. Disconnect the A/T shift lock control solenoid.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the A/T shift lock control supply voltage circuit at the A/T shift lock control solenoid with a test lamp that is connected to a good ground.
  6. With a scan tool, command the Brake to Shift Output ON.

Does the test lamp illuminate?

Go to Step 5

Go to Step 7

5

  1. Connect a test lamp between the A/T shift lock control solenoid supply voltage circuit of the A/T shift lock control solenoid and the ground circuit of the A/T shift lock control solenoid.
  2. With a scan tool, command the Brake to Shift Output ON.

Does the test lamp illuminate?

Go to Step 10

Go to Step 11

6

Test the park neutral position switch park signal circuit of the A/T shift lock control switch for a open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 8

7

Test the A/T shift lock control solenoid supply voltage circuit of the A/T shift lock control solenoid for a open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 9

8

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Computer/Integrating Systems and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

9

  1. Inspect for poor connections at the harness connector of the A/T shift lock control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  2. Inspect for proper adjustment of the A/T shift lock control switch. Refer to Stop Lamp Switch Adjustment in Lighting Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

10

Inspect for poor connections at the harness connector of the A/T shift lock control solenoid. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

11

Repair the ground circuit of the A/T shift lock control solenoid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 15

--

12

Replace the A/T shift lock control switch. Refer to Stop Lamp Switch Replacement in Lighting Systems.

Did you complete the replacement?

Go to Step 15

--

13

Replace the A/T shift lock control solenoid. Refer to Automatic Transmission Shift Lock Actuator Replacement .

Did you complete the replacement?

Go to Step 15

--

14

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 15

--

15

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2