GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

    • If the POWER ACCESSORIES circuit breaker is open, the cause could be one of the following:
       - A short to ground in the battery positive voltage circuit.
       - A short to ground in the door lock relay lock/unlock control circuits. This could open the POWER ACCESSORIES fuse with a lock or unlock switch activation or a keyless entry transmission.
       - A short to ground in the door lock actuator lock/unlock control circuits. This could open the POWER ACCESSORIES fuse with a lock or unlock switch activation or a keyless entry transmission.
    • If battery positive voltage is detected on either of the door lock relay control circuits without a door lock switch activation or a keyless entry transmission, the cause could be one of the following:
       - A short to battery positive voltage in the door lock relay control circuits.
       - A stuck active door lock switch.
       - A malfunctioning door lock relay.
       - A malfunctioning remote control door lock receiver, if equipped.

Step

Action

Yes

No

Schematic Reference: Door Lock/Indicator Schematics

Connector End View Reference: Master Electrical Component List

DEFINITION: This diagnostic should be used to diagnose a failure of either lock or unlock functions and also a complete failure of the Power Door Lock System.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

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

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 or Power Door Lock Inoperative - Driver Door

Go to Step 4

4

  1. Disconnect the door lock relay.
  2. Connect a test lamp between the battery positive voltage circuit at the relay connector and ground .

Did the test lamp illuminate?

Go to Step 5

Go to Step 18

5

Connect a test lamp between the battery positive voltage circuit and the door lock relay ground circuit at the relay connector.

Did the test lamp illuminate?

Go to Step 6

Go to Step 19

6

Connect a test lamp between the door lock relay lock control circuit at the relay connector and ground.

Did the test lamp illuminate?

Go to Step 10

Go to Step 7

7

  1. Connect a test lamp between the door lock relay lock control circuit at the relay connector and ground.
  2. Press a door lock switch to the lock position.

Did the test lamp illuminate?

Go to Step 8

Go to Step 21

8

Connect a test lamp between the door lock relay unlock control circuit at the relay connector and ground.

Did the test lamp illuminate?

Go to Step 10

Go to Step 9

9

  1. Connect a test lamp between the door lock relay unlock control circuit at the relay connector and ground.
  2. Press a door lock switch to the unlock position.

Did the test lamp illuminate?

Go to Step 12

Go to Step 22

10

While monitoring the test lamp still connected to the door lock relay control circuit, disconnect the remote control door lock receiver.

Is the test lamp still illuminated?

Go to Step 11

Go to Step 14

11

While monitoring the test lamp still connected to the door lock relay control circuit, disconnect both door lock switches.

Is the test lamp still illuminated?

Go to Step 20

Go to Step 15

12

  1. Reconnect the door lock relay.
  2. Backprobe the door lock actuator lock circuit at the relay connector with a test lamp connected to a good ground.
  3. Press a door lock switch to the lock position.

Did the test lamp illuminate?

Go to Step 13

Go to Step 16

13

  1. Backprobe the door lock actuator unlock circuit at the relay connector with a test lamp connected to ground.
  2. Press a door lock switch to the unlock position.

Did the test lamp illuminate?

Go to Step 17

Go to Step 16

14

Inspect for poor connections at the remote control door lock receiver harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 26

Go to Step 23

15

Inspect for poor connections at the appropriate door lock switch harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 26

Go to Step 24

16

Inspect for poor connections at the door lock relay harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 26

Go to Step 25

17

Repair the open or short to ground in the door lock actuator lock and or unlock circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

Go to Step 26

--

18

Repair the open or short to ground in the battery positive voltage circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

Go to Step 26

--

19

Repair the open in the relay ground circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

Go to Step 26

--

20

Repair the short to battery in the door lock relay control circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

Go to Step 26

--

21

Repair the open or short to ground in the door lock relay lock control circuit. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 26

--

22

Repair the open or short to ground in the door lock relay unlock control circuit. Refer to Circuit Testing and Wiring Repairs.

Did you complete the repair?

Go to Step 26

--

23

Replace the remote control door lock receiver. Refer to Remote Control Door Lock Receiver Replacement

Did you complete the repair?

Go to Step 26

--

24

Replace the inoperative door lock switch. Refer to Door Lock Switch Replacement.

Did you complete the repair?

Go to Step 26

--

25

Replace the door lock relay.

Did you complete the repair?

Go to Step 26

--

26

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2