GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B3666: Rear Tonneau Position Error

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

B+ - Folding Top Control Module

1

1

--

--

Folding Top Cover Open Switch Signal

B1420

3, 4

B3666

--

Folding Top Cover Ajar Signal

5, 6

B3666,

--

--

Ground - Folding Top Cover Latch Actuator

--

B3666, 2, 3, 5

--

--

Ground - Folding Top Control Module

--

1

--

--

1. No communication with the FTC module.

2. Power folding top is inoperative

3. Power folding top does not open or complete the top opening procedure.

4. Power folding top does not close or complete the top closing procedure.

5. Folding top stowage compartment lid release inoperative

6. DIC Warning Message

Circuit/System Description

The body control module (BCM) supplies ignition voltage to the folding top cover open switch. The folding top control (FTC) module monitors the signal circuit of this switch to determine the open and closed position of the folding top cover. At the same time the 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.

Conditions for Running the DTC

The FTC module must be powered and can not have B1327 or B1328 set as active DTCs for this DTC to set. The battery voltage is between 9-16 volts.

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

    • The folding top operation is suspended.
    • Current and history DTCs are stored.

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.

Diagnostic Aids

    • The Folding Top Cover is also referenced as the Tonneau Cover.
    • The scan tool references the Folding Top Cover Open Switch as the Tonneau Open Limit Switch
    • The scan tool references the Folding Top Cover Latch as the Tonneau Latch Switch

Reference Information

Schematic Reference

Folding Top Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Folding Top Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

When the folding top cover is in the closed position, the following scan tool parameter definitions should be true:

    • Tonneau Open Limit Switch -- The switch is open and the scan tool parameter should be Inactive.
       ⇒If not the specified value, refer to the Folding Top Cover Open Switch Test.
    • Tonneau Latch Switch -- The switch is open and the scan tool parameter should be Closed.
       ⇒If not the specified value, refer to the Folding Top Cover Latch Test

When the folding top cover is in the open position, the following scan tool parameter definitions should be true:

    • Tonneau Open Limit Switch -- The switch is closed to voltage and the scan tool parameter should be Active.
       ⇒If not the specified value, refer to the Folding Top Cover Open Switch Test.
    • Tonneau Latch Switch -- The switch is closed to ground and the scan tool parameter should be Ajar.
       ⇒If not the specified value, refer to the Folding Top Cover Latch Test.

Circuit/System Testing

Folding Top Cover Open Switch Test

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

  1. Ignition OFF, disconnect the harness connector at the folding top cover open switch.
  2. Ignition ON, verify the scan tool Tonneau Open Limit Switch parameter is Inactive.
  3. If not the specified value, test the signal circuit terminal A for a short to voltage. If the circuits test normal, replace the FTC module.
  4. Install a 3A fused jumper wire between the ignition circuit terminal B and the signal circuit terminal A. Verify the scan tool Tonneau Open Limit Switch parameter is Active.
  5. If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the FTC module.
  6. Ignition OFF, disconnect the harness connector at the folding top cover pull down actuator.
  7. Ignition ON, verify the scan tool Power Pull Down Ajar Status parameter is Closed.
  8. If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit test normal, replace the BCM.
  9. If all circuits test normal, test or replace the folding top cover open switch.

Folding Top Cover Latch Test

  1. Ignition OFF, disconnect the X2 harness connector at the folding top cover latch actuator.
  2. Test for less than 5 ohms between the ground circuit terminal B and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Tonneau Latch Switch parameter is Closed.
  5. If not the specified value, test the signal circuit terminal A for a short to ground. If the circuits test normal, replace the FTC module.
  6. Install a 3A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Tonneau Open Limit Switch parameter is Ajar.
  7. If not the specified value, test the signal circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  8. Ignition OFF, disconnect the harness connector at the folding top cover pull down actuator.
  9. Ignition ON, verify the scan tool Power Pull Down Ajar Status parameter is Closed.
  10. If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit test normal, replace the BCM.
  11. If all circuits test normal, test or replace the folding top cover latch actuator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Folding Top Stowage Compartment Lid Latch Replacement
    •  Folding Top Cylinder Replacement
    •  Control Module References for FTC module and BCM replacement, setup, and programming