GM Service Manual Online
For 1990-2009 cars only

Brake Transmission Shift Interlock Inoperative (Lock System Does Not Lock)

Step

Action

Value(s)

Yes

No

DEFINITION: Transmission shifts out of PARK with the ignition switch in ON and brake pedal not depressed.

1

Were you sent here from the Brake Transmission Shift Interlock System Check?

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Go to Step 2

Go to Brake Transmission Shift Interlock System Check

2

  1. Disconnect the park/neutral position switch connector C1.
  2. Connect a DMM between the park/neutral position switch connector C1 terminal C and ground.
  3. Turn the ignition switch to the ON position.
  4. Measure the available voltage at the park/neutral position switch connector C1 terminal C.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 3

Go to Step 8

3

  1. Connect a DMM between the park/neutral position switch terminal C and terminal B.
  2. Place gearshift selector in the PARK position.
  3. Measure for continuity between terminal C and terminal B of the park/neutral position switch.

Is continuity present across the park/neutral position switch when the gearshift selector is placed in PARK?

--

Go to Step 4

Go to Step 9

4

  1. Disconnect the brake transmission shift interlock switch connector.
  2. Connect a DMM between the park/neutral position switch connector C1 terminal B and the brake transmission shift interlock switch connector terminal A.
  3. Measure for continuity between the park/neutral position switch connector C1 terminal B and the brake transmission shift interlock switch connector terminal A.

Is CKT 434 continuous between these two connectors?

--

Go to Step 5

Go to Step 10

5

  1. Connect a DMM between terminal A and terminal B of the brake transmission shift interlock switch.
  2. DO NOT depress the brake pedal.
  3. Measure for continuity between terminal A and terminal B of the brake transmission shift interlock switch.

Is continuity present across the brake transmission shift interlock switch when the brake pedal is not depressed?

--

Go to Step 6

Go to Step 11

6

  1. Disconnect the brake transmission shift interlock control solenoid connector.
  2. Connect a DMM between the brake transmission shift interlock control solenoid connector terminal C and the brake transmission shift interlock switch connector terminal B.
  3. Measure for continuity between the brake transmission shift interlock control solenoid connector terminal C and the brake transmission shift interlock switch connector terminal B.

Is CKT 1135 continuous between these two connectors?

--

Go to Step 18

Go to Step 7

7

Repair the open in CKT 1135.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

8

Check the BTSI BU MiniFuse® #21 for an open.

Is the fuse open?

--

Go to Step 13

Go to Step 12

9

Replace the park/neutral position switch.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

10

Repair the open in CKT 434.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

11

Replace the brake transmission shift interlock switch.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

12

Repair the open in CKT 341.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

13

  1. Remove the BTSI BU MiniFuse® #21.
  2. Leave the park/neutral position switch connector C1 disconnected.
  3. Disconnect the brake transmission shift interlock switch connector.
  4. Disconnect the brake transmission shift interlock control solenoid connector.
  5. Connect a DMM between the park/neutral position switch connector C1 terminal C and ground.
  6. Measure CKT 341 for continuity to ground?

Is CKT 341 continuous to ground?

--

Go to Step 14

Go to Step 15

14

Repair a short to ground in CKT 341.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

15

  1. Connect a DMM between the park/neutral position switch connector C1 terminal B and ground.
  2. Measure CKT 434 for continuity to ground?

Is CKT 434 continuous to ground?

--

Go to Step 16

Go to Step 17

16

Repair a short to ground in CKT 434.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

17

Repair a short to ground in CKT 1135.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

18

  1. Connect a DMM between the brake transmission shift lock control solenoid connector terminal D and ground.
  2. Measure CKT 150 for continuity to ground?

Is CKT 150 continuous to ground?

--

Go to Step 19

Go to Step 20

19

Replace the brake transmission shift lock control solenoid.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

--

20

Repair an open in CKT 150.

Is the repair complete?

--

Go to Brake Transmission Shift Interlock System Check

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