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.

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 Panel Position Sensor 5-Volt Reference

B3665, B3666, B3971

B3665

B3665, B3666, B3670, B3971

--

Front Panel Position Sensor Signal

B3665

B3665

B3665

--

Front Panel 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 Panel Position Sensor 5-Volt Reference

B3665, B3666, B3971

B3666

B3665, B3666, B3670, B3971

--

Rear Panel Position Sensor Signal

B3666

B3666

B3666

--

Rear Panel Position Sensor Low Reference

--

B3666

--

--

Folding Top Pump Motor Temperature Sensor 5-Volt Reference

B3665, B3666, B3971

2, 7

B3665, B3666, B3971, B3670

--

Folding Top Pump Motor Temperature Sensor Signal

2, 7

2, 7

B3670

--

Hard Top Connected Signal

B1420

4, 7

B1310

--

Folding Top Closed Switch Control

B1420

4, 7

--

--

Front Latched Position Switch Signal

B1420, 3, 4, 7

3, 4, 7

B1300

--

Front Latched Position Switch Control

B1420

3, 4, 7

--

--

Front Unlatched Position Switch Signal

B1420, 9

9

B1300

--

Front Unlatched Position Switch Control

B1420

9

--

--

Compartment Partition Position Switch Signal

B1420, 2, 7

2, 7

8

--

Compartment Partition Position 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

--

--

Folding Top Valve 1 Control

1

3

--

--

Folding Top Valve 1 - Ground

--

3

--

--

Folding Top Valve 2 Control

1

4

--

--

Folding Top Valve 2 - Ground

--

4

--

--

Folding Top Valve 3 Control

1

3, 4, 6

--

--

Folding Top Valve 3 - Ground

--

3, 4, 6

--

--

Folding Top Valve 4 Control

1

B1297, 3, 4, 5

--

--

Folding Top Valve 4 - Ground

--

B1297, 3, 4, 5

--

--

Folding Top Valve 5 Control

1

2

--

--

Folding Top Valve 5 - Ground

--

2

--

--

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. 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 rear compartment partition 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 FTC module. The FTC module uses this input information to determine the state and position of the folding top components. Then based on this input, the module then 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.
       - Compartment partition is installed and secured, closing the compartment partition position switch.
       - Vehicle is in PARK.
       - Press the ignition to Accessory 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 folding top control (FTC) module, will display the last status of the items listed.

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

Important: This procedure validates the top opening sequence form the top closed position only. Press and hold the folding top open switch until the top open operation stops or the opening procedure is completed as follows:

  1. Ignition ON, press and continue to hold the folding top open control switch. The events listed below should simultaneously occur.
  2. • The rear compartment lid should unlatch.
    • The front panel should open
    • The front latch should unlatch
    If the rear compartment did not unlatch, refer to Trunk Release Inoperative.
    If the front panel did not open and the front latch did not unlatch, refer to the Valve Test and test valve 5.
  3. After the front panel opens, the scan tool Front Tonneau Status parameter should be Tonneau Open.
  4. If not the specified value, refer to the Front Panel Position Sensor Test.
  5. With the front latch unlatched, the scan tool Header Latch Limit Switches parameter should be Unlatched.
  6. If not the specified value, refer to the Front Unlatched Switch Test.
  7. The rear compartment lid should rise to the open position.
  8. If the rear compartment lid did not rise to the open position, refer to Power Folding Top Inoperative
  9. With the rear compartment lid in the full open position, the scan tool Deck Lid Extended parameter should be Active.
  10. If not the specified value, refer to the Rear Compartment Lid Position Switch Test.
  11. The folding top should move down to the stowed/open position.
  12. If the folding top did not move to the stowed position, refer to the Valve Test and test valve 1.
  13. After the rear panel extends to the closed position, the scan tool Rear Tonneau Status parameter should be Tonneau Closed.
  14. If not the specified value, refer to the Rear Panel Position Sensor Test.
  15. With the folding top in the stowed position, the scan tool Folding Top Status parameter should be Retracted.
  16. If not the specified value, refer to the Folding Top Position Sensor Test.
  17. The front panel should close.
  18. If the front panel does not close, refer to the Valve Test and test valve 3.
  19. With the front panel in the closed position, the scan tool Front Tonneau Status parameter should be Tonneau Closed.
  20. If not the specified value, refer to the Front Panel Position Sensor Test.
  21. The front latch should latch and the scan tool Header Latch Limit Switches parameter should be Latched.
  22. If not the specified value, refer to the Front Latched Switch Test.
  23. After the rear compartment lid closes, the scan tool parameters listed below should be Deck Closed.
  24. • Deck Lid Ajar Status
    • Deck Lid Latch Switch
    If not the specified values, refer to Trunk Release Inoperative.

Circuit/System Testing

Valve Test

  1. Ignition OFF, disconnect the harness connector at the appropriate valve.
  2. Verify that a test lamp illuminates between the ground circuit terminal 2 and B+.
  3. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  4. Connect a test lamp between the control circuit terminal 1 and ground.
  5. Ignition ON, command the Valve On and Off with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  6. 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 control module.
  7. If all circuits test normal, test or replace the folding top pump/motor assembly.

Front Panel Position Sensor Test

  1. With the front panel in the full open position, verify that the scan tool Front Tonneau Position Sensor value is at or slightly greater than the Front Tonneau Open Reference Position value.
  2. If not the specified range, test or replace the front panel position sensor.
  3. With the front panel in the full closed position, verify that the scan tool Front Tonneau Position Sensor value is at or slightly less than the Front Tonneau Close Reference Position value.
  4. If not the specified range, test or replace the front panel position sensor.
  5. If the scan tool readings are normal, replace FTC module.

Folding Top Position Sensor Test

  1. With the folding top in the stowed/open position, verify that the Folding Top Position Sensor value is at or slightly less than the Folding Top Open Reference Position value.
  2. If not the specified range, test or replace the folding top position sensor.
  3. If the scan tool reading is normal, replace FTC module.

Rear Panel Position Sensor Test

  1. With the rear panel in the extended/closed position, verify that the Rear Tonneau Position Sensor value is at or slightly less than the Rear Tonneau Closed Reference Position Value.
  2. If not the specified range, test or replace the rear panel position sensor.
  3. If the scan tool reading is normal, replace FTC module.

Rear Compartment Lid Position Switch Test

  1. Ignition OFF, disconnect the harness connector at the rear compartment lid position switch.
  2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal B and ground.
  3. If the test lamp does not illuminate, test the control circuit for short to ground or an open/high resistance.
  4. Verify the scan tool Deck Lid Extended parameter is Inactive.
  5. If not the specified value, test the signal circuit terminal A for a short to voltage. If the circuit tests normal, replace the FTC module.
  6. Install a 3A fused jumper wire between the signal circuit terminal A and the control circuit terminal B. Verify the scan tool Deck Lid Extended parameter is Active.
  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 FTC module.
  8. If all circuits test normal, test or replace the rear compartment lid position switch.

Front Unlatched Switch Test

  1. Ignition OFF, disconnect the harness connector at the folding top front latch position switch-unlatched.
  2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal B and ground.
  3. If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the control circuit terminal B. Verify the scan tool Header Latch Limit Switches parameter is Unlatched.
  5. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the FTC module.
  6. If all circuits test normal, test or replace the folding top front latch position switch-unlatched.

Front Latched Switch Test

  1. Ignition OFF, disconnect the harness connector at the folding top front latch position switch-latched.
  2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal B and ground.
  3. If the test lamp does not illuminate, test the control circuit for an open/high resistance.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the control circuit terminal B. Verify the scan tool Header Latch Limit Switches parameter is Unlatched.
  5. If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the FTC module.
  6. If all circuits test normal, test or replace the folding top front latch position switch-latched.

Component Testing

Front Latched Switch, Front Unlatched Switch, or Folding Top Closed Switch

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

    •  Folding Top Pump with Motor Replacement
    •  Folding Top Position Switch Replacement
    •  Folding Top Stowage Compartment Front Closeout Panel Position Switch Replacement
    •  Folding Top Stowage Compartment Rear Panel Position Switch Replacement
    •  Folding Top Front Latch Position Sensor Switch Replacement
    •  Folding Top Front Latch Replacement
    •  Folding Top Front Locating Pin Position Switch Replacement
    •  Control Module References for FTC module and BCM replacement, setup, and programming