GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic Starting Point - Roof prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Folding Top Control Module Battery Voltage

1

1

--

--

Folding Top Control Module Control

B1420

B1420

--

--

Folding Top Control Module Ground

--

1, 2

--

--

Folding Top Control Switch Battery Voltage

2

2

--

--

Folding Top Control Switch Close Signal

2

2

B3602

--

Folding Top Control Switch Open Signal

2

2

B3602

--

Front Tonneau Position Sensor 5-Volt Reference

B3665, B3666, B3971

B3665

B3665, B3666, B3670, B3971

--

Front Tonneau Position Sensor Signal

B3665

B3665

B3665

--

Front Tonneau Position Sensor Low Reference

--

B3665

--

--

Folding Top Position Sensor 5-Volt Reference

B3665, B3666, B3971

B3971

B3665, B3666, B3670, B3971

--

Folding Top Position Sensor Signal

B3971

B3971

B3971

--

Folding Top Position Sensor Low Reference

--

B3971

--

--

Rear Tonneau Position Sensor 5-Volt Reference

B3665, B3666, B3971

B3666

B3665, B3666, B3670, B3971

--

Rear Tonneau Position Sensor Signal

B3666

B3666

B3666

--

Rear Tonneau Position Sensor Low Reference

--

B3666

--

--

Folding Top Pump Motor Thermal Sensor 5-Volt Reference

B3665, B3666, B3971

2, 7

B3665, B3666, B3670, B3971

--

Folding Top Pump Motor Signal

2, 7

2, 7

B3670

--

Hard Top Connected Signal

B1420

4, 7

B1310

--

Folding Top Closed Switch Control

B1420

4, 7

--

--

Header Latched Switch Signal

B1420, 3, 4, 7

3, 4, 7

B1300

--

Header Latched Switch Control

B1420

3, 4, 7

--

--

Header Unlatched Switch Signal

B1420, 9

9

B1300

--

Header Unlatched Switch Control

B1420

9

--

--

Luggage Barrier Switch Signal

B1420, 2, 7

2, 7

8

--

Luggage Barrier Switch Control

B1420

2, 7

--

--

Pump Direction A Control

B1011

2

--

--

Pump Direction B Control

B1011

2

--

--

Rear Compartment Lid Open Switch Signal

B1420, 3, 4

3, 4

B3669

--

Rear Compartment Lid Open Switch Control

B1420

3, 4

--

--

Valve 1 Control

1

3

--

--

Valve 1 - Ground

--

3

--

--

Valve 2 Control

1

4

--

--

Valve 2 - Ground

--

4

--

--

Valve 3 Control

1

3, 4, 6

--

--

Valve 3 - Ground

--

3, 4, 6

--

--

Valve 4 Control

1

B1297, 3, 4, 5

--

--

Valve 4 - Ground

--

B1297, 3, 4, 5

--

--

Valve 5 Control

1

2

--

--

Valve 5 - Ground

--

2

--

--

1. No communication with the folding top control 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. Rear Compartment lid will not open

6. Rear compartment lid will not close

7. DIC warning message displayed

8. Folding top will operate with the luggage barrier removed

9. No effect on power folding top operation

Circuit/System Description

The power folding top system uses seven different position or limit switches and three position sensors that provide input information to the folding top control (FTC) module. The folding top module uses this input information to determine the state and position of the folding top components. Then based on these inputs, the module applies battery voltage to the appropriate control circuits to the folding top pump motor and the appropriate valves in order to control the hydraulic system used to operate the folding top.

Diagnostic Aids

    • Complete the check list, prior to performing the diagnosis:
       - When the folding top control switch is pressed, check for driver information center (DIC) warning messages.
       - Windows are normalized. Refer to Power Window Reinitialization.
       - Luggage barrier is installed and secured, closing the luggage barrier switch.
       - Vehicle is in PARK.
       - Press the ignition to ACCY or RUN, with the engine OFF.
       - Hydraulic fluid bypass valve in the operating position, turned clockwise, located above the pump motor.
       - Operating temperature is normal.
    • Whenever the open/close control switch is released or the top becomes inoperative in a suspended state, pressure will be maintained in the hydraulic system to avoid drifting and damage of components. After 4 minutes, the FTC module will gradually release the hydraulic pressure allowing the top to gradually settle to a resting position.
    • When using the scan tool, the Rear Compartment Lid is referenced as the Deck Lid.
    • If a repair is made to a signal circuit for a short to ground, test the component of that circuit for proper operation.
    • Using the scan tool to access the History parameters for the FTC module, will display the last status of the items listed.

Reference Information

Schematic Reference

Folding Top Schematics

Connector End View Reference

Power Roof Systems 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

  1. Ignition ON, observe the driver information center (DIC) while pressing the appropriate top open or close switch. No warning messages should be displayed as a result of top operation.
  2. If the DIC displays Close Cargo Cover, refer to the Luggage Barrier Switch Test.
    If the DIC displays Valet Active Top Inop, refer to the Valet Switch Test.
    If the DIC displays Too Cold to Move Top, refer to the Thermal Sensor Test.
  3. Regardless of the tops position, attempt to open or close the folding top. The top should not move in the commanded direction.
  4. If the top attempts to open then stops, refer to Power Folding Top Does Not Open.
    If the top attempts to close then stops, refer to Power Folding Top Does Not Close.
  5. While pressing the top open and top close control switches, verify the scan tool Top Control Switch parameter toggles between Top Open, Top Closed and Idle.
  6. If not the specified values, refer to the Folding Top Control Switch Test.
  7. Verify the scan tool Driver Door Module Window Normalization parameter is Yes.
  8. If not the specified value, refer to Power Windows Description and Operation.
  9. Verify the scan tool Passenger Door Module Window Normalization parameter is Yes.
  10. If not the specified value, refer to Power Windows Description and Operation.
  11. If all tests pass, refer to the Folding Top Inoperative Test.

Circuit/System Testing

Luggage Barrier Switch Test

  1. Ignition OFF, disconnect the harness connector at the luggage barrier switch.
  2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal A and ground.
  3. If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.
  4. Verify the scan tool Luggage Barrier Limit Switch parameter is Open.
  5. If not the specified value, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the folding top module.
  6. Install a 3A fused jumper wire between the signal circuit terminal B and the control circuit terminal A. Verify the scan tool Luggage Barrier Limit Switch parameter is Closed.
  7. If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the folding top module.
  8. If all circuits test normal, test or replace the luggage barrier switch.

Valet Switch Test

  1. Ignition OFF, disconnect the harness connector at the valet switch.
  2. Test for less than 1 ohm between the ground circuit terminal A and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Verify the scan tool HVAC Valet Switch parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the HVAC control module.
  6. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HVAC Valet Switch parameter is Active.
  7. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  8. If all circuits test normal, test or replace the valet switch.

Thermal Sensor Test

  1. Ignition OFF, disconnect the harness connector at the folding top pump motor thermal sensor.
  2. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal D and ground.
  3. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the folding top module.
    If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the folding top module.
  4. Verify the scan tool Pump Motor Temp. Sensor parameter is less than 38 Counts.
  5. If greater than the specified range, test the signal circuit terminal C for a short to voltage. If the circuit tests normal, replace the folding top module.
  6. Install a 3A fused jumper wire between the signal circuit terminal C and the 5-volt reference circuit terminal D. Verify the scan tool Pump Motor. Sensor parameter is greater than 242 Counts.
  7. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the folding top module.
  8. If all circuits test normal, test or replace the pump and valve assembly.

Folding Top Control Switch Test

  1. Ignition OFF, disconnect the harness connector at the folding top control switch.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 4 and ground.
  3. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify the scan tool Top Control Switches parameter is Idle.
  5. If not the specified value, test the signal circuits terminal 1 and terminal 2 for a short to voltage. If the circuits test normal, replace the folding top module.
  6. Connect a 3A fused jumper wire between the signal circuit terminal 1 and the B+ circuit terminal 4. Verify the scan tool Top Control Switches parameter is Top Open
  7. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the folding top module.
  8. Connect a 3A fused jumper wire between the signal circuit terminal 2 and the B+ circuit terminal 4. Verify the scan tool Top Control Switches parameter is Top Closed
  9. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the folding top module.
  10. If all circuits test normal, test or replace the folding top control switch.

Folding Top Inoperative Test

  1. Ignition OFF, disconnect the C1 harness connector at the folding top module.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A and ground.
  3. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify that a test lamp illuminates between the ground circuit terminal B and B+.
  5. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  6. Ignition OFF, connect the C1 harness connector at the folding top module and disconnect the harness connector at the folding top pump motor.
  7. Connect a test lamp between control circuit terminal A and control circuit terminal B.
  8. Ignition ON, command Pump Motor A Direction and Pump Motor B Direction On and Off with a scan tool. The test lamp should turn ON when commanding the pump motor in the A and B directions.
  9. If the test lamp remains OFF during either of the commands, test the control circuits for a short to ground or an open/high resistance. If the circuits test normal, replace the folding top module.
  10. Ignition OFF, disconnect the harness connector at valve 3.
  11. Verify that a test lamp illuminates between the ground circuit terminal 2 and B+.
  12. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  13. Connect a test lamp between the control circuit terminal 1 and ground.
  14. Ignition ON, command Valve 3 ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  15. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the folding top module.
  16. Ignition OFF, disconnect the harness connector at valve 4.
  17. Verify that a test lamp illuminates between the ground circuit terminal 2 and B+.
  18. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  19. Connect a test lamp between the control circuit terminal 1 and ground.
  20. Ignition ON, command Valve 4 ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  21. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the folding top module.
  22. Ignition OFF, disconnect the harness connector at valve 5.
  23. Verify that a test lamp illuminates between the ground circuit terminal 2 and B+.
  24. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  25. Connect a test lamp between the control circuit terminal 1 and ground.
  26. Ignition ON, command Valve 5 ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  27. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the folding top module.
  28. If all circuits test normal, test or replace the pump and valve assembly.

Component Testing

Folding Top Control Switch

  1. Ignition OFF, disconnect the harness connector at the folding top control switch.
  2. Test for infinite resistance between the signal terminal 1 and the B+ terminal 4 with the switch in the open position.
  3. If not the specified value, replace the folding top control switch.
  4. Test for less than 1 ohm between the signal terminal 1 and the B+ terminal 4 with the switch in the closed position.
  5. If not the specified value, replace the folding top control switch.
  6. Test for infinite resistance between the signal terminal 2 and the B+ terminal 4 with the switch in the open position.
  7. If not the specified value, replace the folding top control switch.
  8. Test for less than 1 ohm between the signal terminal 2 and the B+ terminal 4 with the switch in the closed position.
  9. If not the specified value, replace the folding top control switch.

Repair Instructions

Important: Perform the Power Folding Top Learn after component replacement.

    •  Roof Lift Off Panel/Window Latch Trim Cover Replacement
    •  Rear Compartment Lid Valet Lock Out Switch Replacement
    •  Folding Top Pump with Motor Replacement
    •  Convertible Top Switch Replacement
    •  Control Module References for folding top module and HVAC control module replacement, setup, and programming