GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The folding top control (FTC) module supplies accessory voltage to the folding top cover open limit switch. It monitors the signal circuit of this switch to determine the open and closed position of the folding top cover. At the same time the body control module (BCM) supplies battery voltage to the folding top cover latch ajar switch and monitors this circuit to determine if the folding top cover is latched or unlatched. The BCM communicates the status of the folding top cover latch ajar switch via class 2 message to the FTC module.

When the folding top cover is in the closed position the following definitions of the folding top cover latch and the folding top cover open limit switch should be true:

    • Tonneau open limit switch-The switch is open and the scan tool parameter should display Inactive.
    • Tonneau latch switch-The switch is open and the scan tool parameter should display Closed.

When the folding top cover is in the open position, the following definitions of the folding top cover latch and the folding top cover open limit switch should be true:

    • Tonneau open limit switch-The switch is closed to voltage and the scan tool parameter should display Active.
    • Tonneau latch switch-The switch is closed to ground and the scan tool parameter should display Ajar.

DTC Descriptor

The diagnostic procedure supports the following DTC:

DTC B3666 Rear Tonneau Position Error

Conditions for Running the DTC

The FTC module must be powered and cannot have B1327 or B1328 set as active DTCs for this DTC to set.

Conditions for Setting the DTC

DTC B3666 will set as a current DTC, if the FTC module senses that the folding top cover latch is not ajar while the folding top cover open limit switch is active.

Action Taken When the DTC Sets

    • Stores a current and history DTC B3666 in the FTC module.
    • The folding top operation is suspended.
    • The FTC module will send a class 2 message to the driver information center (DIC) to display TOP NOT SECURE.

Conditions for Clearing the DTC

    • This DTC will clear on the current status after the condition for setting the fault is corrected.
    • A history DTC will clear after 50 consecutive ignition cycles without a fault present.
    • History and current DTC can be cleared using the scan tool.

Diagnostic Aids

    • When using the scan tool the folding top cover is referenced as the tonneau.
    • The folding top cover must be in the fully open position with the switch closed to battery voltage for B3666 to be a current DTC.
    • If the DTC does not reset after the code is cleared, then the switch may be the intermittent fault. Refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. This step determines the integrity of the folding top cover latch. The folding top cover must be in the open position with the tonneau limit switch parameter displaying Active in order for this step to be a valid test.

  2. This step determines the integrity of the folding top cover open limit switch. The folding top cover must be closed and latched in order for this step to be a valid test.

  3. This step determines the integrity of the folding top cover pull down ajar signal circuit. A short to ground in this circuit may have inadvertently set this DTC.

Step

Action

Yes

No

Schematic Reference: Folding Top Schematics

Connector End View Reference: Folding Top Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 3

Go to Diagnostic System Check - Vehicle

2

  1. Use the scan tool in order to clear the DTC.
  2. Operate the power folding top to the top open and top closed positions.

Did the DTC reset?

Go to Step 3

Go to Diagnostic Aids

3

Determine the open or closed position of the folding top cover.

Is the folding top cover in the open position?

Go to Step 4

Go to Step 5

4

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. 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 9

Go to Step 6

5

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Tonneau Open Limit Switch parameter in the Folding Top Module Inputs data list.

Does the Tonneau Open Limit Switch parameter display Active?

Go to Step 8

Go to Step 9

6

  1. Turn OFF the ignition.
  2. Disconnect the folding top cover latch actuator connector C2.
  3. Connect a 3-amp fused jumper wire from the folding top cover ajar signal circuit of the latch connector to a good ground.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, observe the Tonneau Latch Switch parameter.

Does the Tonneau Latch Switch parameter display Ajar?

Go to Step 7

Go to Step 10

7

  1. Connect the 3-amp fused jumper wire from the folding top cover ajar signal circuit of the latch connector to the ground circuit of the latch connector.
  2. With a scan tool, observe the Tonneau Latch Switch parameter.

Does the Tonneau Latch Switch parameter display Ajar?

Go to Step 13

Go to Step 17

8

  1. Turn OFF the ignition.
  2. Disconnect the folding top cover open limit switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Tonneau Open Limit Switch parameter.

Does the Tonneau Open Limit Switch parameter display Active?

Go to Step 11

Go to Step 14

9

  1. Disconnect the folding top cover pull down actuator harness connector.
  2. With a scan tool observe the Power Pull Down Ajar Status parameter.

Does the Power Pull Down Ajar Status parameter display Ajar?

Go to Step 12

Go to Testing for Intermittent Conditions and Poor Connections

10

Test the folding top cover ajar signal circuit for an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 22

Go to Step 16

11

Test the signal circuit of the folding top cover open limit switch for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 22

Go to Step 15

12

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

Did you find and correct the condition?

Go to Step 22

Go to Step 16

13

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

Did you find and correct the condition?

Go to Step 22

Go to Step 18

14

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

Did you find and correct the condition?

Go to Step 22

Go to Step 19

15

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 22

Go to Step 20

16

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

Did you find and correct the condition?

Go to Step 22

Go to Step 21

17

Repair the high resistance or open in the ground circuit of the folding top latch actuator connector C2. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 22

--

18

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

Did you complete the replacement?

Go to Step 22

--

19

Important: The folding top cover open limit switch is an internal part of the folding top cover hydraulic cylinder assembly that is not serviced separately.

Replace the folding top cover open limit switch. Refer to Folding Top Cylinder Replacement .

Did you complete the replacement?

Go to Step 22

--

20

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

Did you complete the replacement?

Go to Step 22

--

21

Replace the BCM. Refer to Control Module References .

Did you complete the replacement?

Go to Step 22

--

22

  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 3

System OK