GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The lower left endgate ajar switch signal and upper right endgate ajar switch signal circuits provide input to the endgate module. These inputs are used for endgate swing latch and drop latch requests. If the endgate module detects an open on the lower left endgate ajar switch signal circuit when a drop latch request is made, or an open on the upper right endgate ajar switch signal circuit when a swing latch request is made, a DTC is set.

DTC Descriptor

This diagnostic procedure supports the following DTCs:

    • DTC B1539 Lower Left Endgate Ajar Switch Circuit
    • DTC B1540 Upper Right Endgate Ajar Switch Circuit

Conditions for Setting the DTC

    • The endgate module detects an open on a lower left endgate ajar switch signal or upper right endgate ajar switch signal circuit.
    • Condition must be present when a drop latch request or swing latch request is made.

Action Taken When the DTC Sets

    • Stores a current DTC B1539 or B1540 in endgate module memory.
    • Stores a history DTC B1539 or B1540 in endgate module memory.
    • The roof module will ignore the drop latch request if DTC B1539 is set.
    • The roof module will ignore the swing latch request if DTC B1540 is set.

Conditions for Clearing the DTC

    • The endgate module no longer detects a current DTC B1539 or B1540 in endgate module memory.
    • The DTC is cleared using a scan tool.

Diagnostic Aids

    • The following conditions may cause an intermittent malfunction:
       - There is an intermittent open in a endgate ajar switch signal circuit.
       - A switch is open internally.
    • If the DTC does not reset after the code is cleared, then the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for an open ajar switch.

  2. Tests for an open in an endgate ajar switch signal circuit or endgate ajar switch low reference circuit.

Step

Action

Yes

No

Schematic Reference: Body Rear End Schematics

Connector End View Reference: Body Rear End Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Open the endgate.
  4. With a scan tool, observe the appropriate Ajar Switch parameter in the endgate module data list.

Does the scan tool display Ajar?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

  1. Disconnect the appropriate endgate latch harness connector.
  2. Connect a test lamp between the endgate ajar switch signal circuit and the endgate ajar switch low reference circuit of the appropriate endgate latch harness connector.

Does the test lamp illuminate?

Go to Step 6

Go to Step 4

4

Connect a test lamp between the endgate ajar switch signal circuit of the appropriate endgate latch harness connector and a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 5

5

Test the appropriate endgate ajar switch signal circuit for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 7

6

Inspect for poor connections at the harness connector of the appropriate endgate latch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

Inspect for poor connections at the harness connector of the endgate module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Repair the open in the endgate ajar switch low reference circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 11

--

9

Replace the appropriate endgate latch. Refer to Endgate Latch Replacement - Right Side Upper or Endgate Latch Replacement - Left Side Lower .

Did you complete the replacement?

Go to Step 11

--

10

  1. Perform the endgate window learn procedure. Refer to Control Module References for replacement, setup, and programming.
  2. Replace the endgate module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 11

--

11

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK