GM Service Manual Online
For 1990-2009 cars only

Test Description

  1. The MIR/LOCK fuse supplies battery positive voltage for the power mirrors, power door lock switches and the memory seat switch, if equipped. If the MIR/LOCK fuse is open, all systems on the fuse would be inoperative. The fault could be a short to ground in the battery positive voltage circuit, however, a short to ground in the power mirror motor control or the memory seat control circuits could also be the cause if the fuse opens after any of the switches are activated. If a short to ground exists in either the door lock or unlock relay control circuits, a DTC B3137 or B3147 would set when the BCM commands a lock or unlock function.

Step

Action

Yes

No

Schematic Reference: Door Lock/Indicator Schematics

DEFINITION: This diagnostic should be used to diagnose a complete failure of the power door lock system lock and unlock. This diagnostic assumes that all the system fuses have been checked for an open and that any shorts to ground in the battery positive voltage circuits have been repaired. If the power door lock system is still inoperative after the battery positive voltage circuits have been repaired and the fuses replaced, continue with the diagnosis.

1

Did you perform the Power Door System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Door Systems

2

Actuate all door lock switches to both the lock and unlock positions.

Did all the doors lock and unlock?

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

Go to Step 3

3

Did any of the doors lock and unlock from any of the switches?

Go to Power Door Locks Inoperative - One Door or Switch

Go to Step 4

4

  1. Install a scan tool.
  2. With the scan tool, command the doors to lock and unlock.

Did the doors lock and unlock?

Go to Step 12

Go to Step 5

5

  1. Remove the door lock relay.
  2. With a test lamp connected to a good ground, test the battery positive voltage circuits for the door lock relay at the fuse block.

Did the test lamp illuminate?

Go to Step 6

Go to Step 13

6

With a test lamp connected to B+, test the ground circuits for the door lock relay at the fuse block.

Did the test lamp illuminate?

Go to Step 7

Go to Step 14

7

Connect a test lamp between the door lock actuator lock circuit at the fuse block and a good ground.

Did the test lamp illuminate?

Go to Step 8

Go to Step 9

8

  1. Remove the door unlock relay.
  2. Connect a test lamp between the door unlock relay control circuit and B+.

Did the test lamp illuminate?

Go to Step 11

Go to Step 16

9

  1. With a test lamp still connected between the door lock actuator lock circuit at the fuse block and a good ground.
  2. Actuate a door lock switch to the unlock position.

Did the test lamp illuminate?

Go to Step 15

Go to Step 10

10

  1. Install the door lock relay.
  2. Remove the door unlock relay.
  3. Connect a test lamp between the door lock actuator unlock circuit at the fuse block and a good ground.
  4. Actuate a door lock switch to the lock position.

Did the test lamp illuminate?

Go to Step 16

Go to Step 17

11

Test for a short to ground in the door unlock relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

12

Repair the open or short to ground in the battery positive voltage circuit between the MIR/LOCK fuse and the door lock switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

13

Repair the open or short to ground in the battery positive voltage supply circuit between the DR LOCK fuse and the door lock and unlock relays. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

14

Repair the open in the ground circuit for the door lock and unlock relays. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

15

Replace the door lock relay.

Did you complete the repair?

Go to Step 19

--

16

Replace the door unlock relay.

Did you complete the repair?

Go to Step 19

--

17

Repair the open in the door lock actuator lock and/or unlock circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

18

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the repair?

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4