GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Shift Lock Control Schematics

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 Symptoms - Automatic Transmission Shift Lock Control tests and perform all the necessary inspections?

Go to Step 2

Go to Symptoms - Automatic Transmission Shift Lock Control

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.

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. Move the shift lever to the PARK position.
  2. Connect a test lamp between the automatic transmission shift lock control switch ignition 1 circuit at the automatic transmission shift lock control switch and a good ground.
  3. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 4

Go to Step 12

4

Connect a test lamp between the A/T shift lock control solenoid supply voltage circuit at the automatic transmission shift lock control switch and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 9

5

Connect a test lamp between the A/T shift lock control solenoid supply voltage circuit at the automatic transmission shift lock control solenoid and a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 13

6

Connect a test lamp between the neutral safety switch signal circuit at the automatic transmission shift lock control solenoid and battery positive voltage.

Does the test lamp illuminate?

Go to Step 10

Go to Step 7

7

Connect a test lamp between the neutral safety switch signal circuit at the park/neutral position switch and battery positive voltage.

Does the test lamp illuminate?

Go to Step 14

Go to Step 8

8

Connect a test lamp between the park/neutral position switch ground circuit at the park/neutral position switch and battery positive voltage.

Does the test lamp illuminate?

Go to Step 11

Go to Step 15

9

  1. Inspect the automatic transmission shift lock control switch for proper adjustment. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes.
  2. Inspect for poor connections at the automatic transmission shift lock control switch. 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 19

Go to Step 16

10

Inspect for poor connections at the automatic transmission 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 19

Go to Step 17

11

  1. Inspect for proper park/neutral position switch adjustment. Refer to Park/Neutral Position Switch Adjustment in Automatic Transmission.
  2. Inspect for poor connections at the park/neutral position switch. 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 19

Go to Step 18

12

Repair the open in the ignition 1 circuit of the automatic transmission shift lock control switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

13

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

Did you complete the repair?

Go to Step 19

--

14

Repair open in the neutral safety switch signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

15

Repair the open park/neutral position switch ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

16

Replace the automatic transmission shift lock control switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Did you complete the replacement?

Go to Step 19

--

17

Replace the automatic transmission shift lock control solenoid. Refer to Automatic Transmission Shift Lock Actuator Replacement .

Did you complete the repair?

Go to Step 19

--

18

Replace park/neutral position switch. Refer to Park/Neutral Position Switch Replacement in Automatic Transmission.

Did you complete the replacement?

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2