GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

    • When using the scan tool, the folding top cover is referenced as the tonneau.
    • If a repair is made to a signal circuit for a short to ground, test the component of that circuit for proper operation.
    • Removing the tonneau release relay will set a DTC and stop power folding top operation. Once the relay is replaced, the ignition must be cycled OFF then Run ACCY in order to continue operation.
    • Using the scan tool to access the History parameters for the folding top control (FTC) module, will display the last status of the items listed.

Test Description

  1. This step verifies the open or closed position of the power folding top.

  2. This step verifies that the body control module (BCM) is applying battery voltage to the control circuit of the tonneau release relay. Removing the tonneau release relay will set DTC B3637 causing the BCM to disable output control of the relay until the ignition is cycled OFF/Run ACCY. After the test lamp is connected in place of the relay, the ignition must be cycled OFF/Run ACC in order for this step to be a valid test.

Step

Action

Yes

No

Schematic Reference: Folding Top Schematics

Connector End View Reference: Folding Top Connector End Views

Important: This diagnostic table is to be used only in conjunction with other diagnostic procedures in this section. Using this diagnostic table without being directed to its use, may result in the misdiagnoses of the power folding top system.

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Verify that the folding top folding top cover latch actuator or folding top cover pull down actuator inoperative complaint is present.

Does the folding top cover latch actuator and folding top cover pull down actuator systems operate as described in the system description and operation?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Does the folding top cover pull down actuator continuously move up and down?

Go to Step 4

Go to Step 5

4

Is the folding top cover in the open position?

Go to Step 30

Go to Step 11

5

During the folding top operation when the sequence is reached for the folding top cover to open, did the folding top cover unlatch?

Go to Step 7

Go to Step 6

6

Is the folding top in the open position?

Go to Step 12

Go to Step 15

7

During folding top operation, after the folding top cover released and opened, did the folding top cover pull down actuator extend to the up position?

Go to Step 8

Go to Step 23

8

During the folding top operation when the folding top cover closed, did the folding top cover latch?

Go to Step 9

Go to Step 10

9

During folding top operation, after the folding top cover closed, did the folding top cover pull down actuator retract to the down position?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 22

10

  1. Disconnect the folding top cover latch actuator harness connector C1.
  2. Probe the folding top cover latch actuator control circuit of the connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 26

Go to Step 35

11

  1. Disconnect the folding top cover pull down actuator harness connector.
  2. With a scan tool, observe the Power Pull Down Ajar Status parameter in the Folding Top Module Inputs data list.

Does the Power Pull Down Ajar Status parameter display Ajar?

Go to Step 28

Go to Step 36

12

With a scan tool, observe the Top Open Limit Switch parameter in the Folding Top Module Inputs data list.

Does the Top Open Limit Switch parameter display Active?

Go to Step 15

Go to Step 13

13

  1. Disconnect the top open switch harness connector.
  2. Connect a test lamp from the accessory voltage circuit of the switch connector to a good ground.

Does the test lamp illuminate?

Go to Step 14

Go to Step 37

14

  1. Connect a 3-amp fused jumper wire between the accessory voltage circuit of the top open switch connector and the signal circuit of the top open switch connector.
  2. With a scan tool, observe the Top Open Limit Switch parameter in the Folding Top Module Inputs data list.

Does the Top Open Limit Switch parameter display Active?

Go to Step 31

Go to Step 25

15

With a scan tool, observe the Tonneau Latch Switch parameter in the Folding Top Module Inputs data list.

Does the Tonneau Latch Switch parameter display Ajar?

Go to Step 16

Go to Step 17

16

  1. Disconnect the folding top cover latch actuator harness connector C2.
  2. With a scan tool, observe the Tonneau Latch Sw. parameter.

Does the Tonneau Latch Sw. parameter display Ajar?

Go to Step 27

Go to Step 35

17

  1. Turn OFF the ignition.
  2. Remove the tonneau release relay. Refer to Relay Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the relay connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 18

Go to Step 38

18

  1. With a scan tool navigate to the Miscellaneous Tests screen by making the following selections:
  2. • Vehicle Control Systems
    • Special Functions
    • Body Control Module
  3. Connect a test lamp from the folding top cover release control circuit of the tonneau release relay connector to a good ground.
  4. Cycle the ignition OFF to Run ACCY.
  5. With a scan tool command the tonneau relay ON.

Does the test lamp illuminate when the relay is commanded ON?

Go to Step 19

Go to Step 33

19

Connect a 3-amp fused jumper wire between the battery positive voltage circuit of the tonneau release relay connector and the folding top cover latch actuator control circuit of the relay connector.

Did the folding top cover unlatch?

Go to Step 34

Go to Step 20

20

  1. Leave the a 3-amp fused jumper wire connected between the battery positive voltage circuit of the tonneau release relay and the folding top cover latch actuator control circuit of the tonneau release relay connector.
  2. Disconnect the folding top cover latch actuator harness connector C1.
  3. Probe the control circuit of the folding top cover latch actuator connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 21

Go to Step 39

21

  1. Leave the 3-amp fused jumper wire connected between the battery positive voltage circuit of the tonneau release relay connector and the folding top cover latch actuator control circuit of the tonneau release relay connector.
  2. Connect the test lamp between the control circuit of the folding top cover latch actuator connector and the ground circuit of the folding top cover latch actuator connector.

Does the test lamp illuminate?

Go to Step 35

Go to Step 41

22

  1. Disconnect the folding top cover latch actuator harness connector C2.
  2. Connect a 3-amp fused jumper wire from the folding top cover pull down actuator control circuit of the folding top cover latch actuator connector to a good ground.

Did the folding top cover pull down actuator retract to the down position?

Go to Step 35

Go to Step 23

23

  1. Disconnect the folding top cover pull down actuator harness connector.
  2. Probe the battery positive voltage circuit of the folding top cover pull down actuator connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 24

Go to Step 40

24

Connect the test lamp between the battery positive voltage circuit of the pull down actuator connector and the ground circuit of the pull down actuator connector.

Does the test lamp illuminate?

Go to Step 29

Go to Step 42

25

Test the signal circuit of the top open switch for an open. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 32

26

Test the folding top cover latch actuator control circuit, between the tonneau release relay and the folding top cover latch actuator, for a short battery voltage. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 34

27

Test the folding top cover latch ajar signal circuit for a short to ground. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 33

28

Test the folding top cover pull down ajar signal circuit for a short to ground. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 33

29

Test the pull down actuator control circuit, between the folding top cover latch actuator and the folding top cover pull down actuator, for an open. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 30

30

Test the pull down actuator control circuit, between the folding top cover latch actuator and the folding top cover pull down actuator, for a short to ground. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 36

31

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

Did you find and correct the condition?

Go to Step 49

Go to Step 43

32

Inspect for poor connections at the harness connector of the folding top control (FTC) module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 44

33

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 45

34

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

Did you find and correct the condition?

Go to Step 49

Go to Step 46

35

Inspect for poor connections at the harness connector folding top cover latch actuator. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 47

36

Inspect for poor connections at the harness connector of the folding top cover pull down actuator. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

Go to Step 49

Go to Step 48

37

Repair the open in the accessory voltage circuit of the top open switch. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

--

38

Repair the short to ground or open in the battery positive voltage circuit of the tonneau release relay. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

--

39

Repair the short to ground or open in the control circuit of the folding top cover latch actuator. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

--

40

Repair the short to ground or open in the battery positive voltage circuit of the folding top cover pull down actuator. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 49

--

41

Repair the open in the ground circuit of the folding top cover latch actuator. Refer to Wiring Repairs .

Did you find and correct the condition?

Go to Step 49

--

42

Repair the open in the ground circuit of the folding top cover pull down actuator. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 49

--

43

Replace the top open switch. Refer to Folding Top Position Switch Replacement .

Did you complete the replacement?

Go to Step 49

--

44

Replace the FTC module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 49

--

45

Replace the BCM. Refer to Control Module References .

Did you complete the replacement?

Go to Step 49

--

46

Replace the tonneau release relay.

Did you complete the replacement?

Go to Step 49

--

47

Replace the folding top cover latch actuator. Refer to Folding Top Stowage Compartment Lid Latch Replacement .

Did you complete the replacement?

Go to Step 49

--

48

Replace the folding top cover pull down actuator. Refer to Folding Top Stowage Compartment Lid Latch Striker Replacement .

Did you complete the replacement?

Go to Step 49

--

49

  1. Turn OFF the ignition.
  2. Disconnect any jumper wires.
  3. Connect all previously disconnected components.
  4. Replace any open fuses, if necessary.
  5. Press the ignition to ACCY or RUN, with the engine OFF.
  6. Use the scan tool to clear any DTCs.
  7. Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2