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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Corvette 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Power Folding Top Does Not Open

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

B+ - Folding Top Control Module

1

1

--

--

Ignition Voltage - 5 Bow Raised Switch

B1420

3, 4

--

--

Ignition Voltage - Folding Cover Open Switch

B1420

3, 4

--

--

Ignition Voltage - Top Closed Switch

B1420

3, 4

--

--

Ignition Voltage - Top Open Switch

B1420

3, 4, 6

--

--

5 Bow Raised Switch Signal

B1420

3, 4

B1291

--

Folding Top Cover Open Switch Signal

B1420

3, 4

B3666

--

Folding Top Cover Pull Down Ajar Signal

2, 3, 5

3, 4

--

--

Top Closed Switch Signal

B1420

3, 4

B3971

--

Top Open Switch Signal

B1420

3, 4, 6

B3971

--

Folding Top Motor Valve 1 Control

3, 4, 6

3, 4, 6

--

--

Ground - Folding Top Motor Valve 1

--

3, 4, 6

--

--

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 cover pull down actuator continuously moves up and down

6. The folding top cover will not open

Circuit/System Description

The power folding top system uses seven different position or limit switches 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.
       - Luggage barrier is installed and secured, closing the luggage barrier switch.
       - Vehicle is in PARK or the park brake is applied with manual transmission.
       - 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.
       - Pump operating temperature is between 18°C (0°F) and 95°C (199°F).
    • 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 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.
    • 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 opening operation stops or the opening procedure is completed as follows:

  1. Ignition ON, observe the driver information center (DIC) while pressing and continuing to hold the folding top open switch. No warning messages should be displayed as a result of top operation.
    2. ⇒If warning messages are displayed, refer to DIC Warning Messages - Roof.
  2. Press and continue to hold the folding top open switch. After the 5 bow raised to the up position, observe the scan tool 5 Bow Raised Pos. Switch parameter, the reading should be Active.
    3. ⇒If not the specified value, refer to the 5 Bow Raised Switch Test.
  3. Observe the scan tool Top Closed Limit Switch parameter, the reading should be Active.
    4. ⇒If not the specified value, refer to the Top Closed Switch Test.
  4. With the 5 bow in the raised position, the folding top cover should unlatch and rise to the open position.
    5. ⇒If the folding top cover did not unlatch, refer to Folding Top Stowage Compartment Lid Release Inoperative.
    ⇒If the folding top cover unlatched but did not rise to the open position, refer to the Valve 1 Test.
  5. With the folding top cover in the open position, observe the scan tool Tonneau Open Limit Switch parameter, the reading should be Active.
    6. ⇒If not the specified value, refer to the Folding Top Cover Open Switch Test.
  6. After the folding top cover opened, the folding top cover pull down actuator should extend to the up position.
    7. ⇒If the pull down actuator did not extend to the up position, refer to Folding Top Stowage Compartment Lid Release Inoperative.
  7. With the folding top in the stowed position observe the scan tool Top Open Limit Switch parameter, the reading should be Active.
    8. ⇒If not the specified value, refer to the Top Open Switch Test.
  8. Observe the scan tool Power Pull Down Ajar Status parameter, the reading should be Ajar.
    9. ⇒If not the specified value, refer to the Folding Top Pull Down Ajar Test.
  9. After the folding top cover has closed and latched, the folding top cover pull down actuator should retract to the down position.
    10. ⇒If the folding top cover pull down actuator did not retract, refer to Folding Top Stowage Compartment Lid Release Inoperative.

Circuit/System Testing

5 Bow Raised Switch Test

  1. Ignition OFF, disconnect the harness connector at the 5 bow raised switch.
  2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B and ground.
    3. ⇒If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
  3. Verify the scan tool 5 Bow Raised Pos. Switch parameter is Inactive.
    4. ⇒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.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the ignition circuit terminal B. Verify the scan tool 5 Bow Raised Pos. Switch parameter is Active.
    5. ⇒If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the FTC module.
  5. If all circuits test normal, test or replace the 5 bow raised switch.

Top Closed Switch Test

  1. Ignition OFF, disconnect the harness connector at the top closed switch.
  2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B and ground.
    3. ⇒If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
  3. Verify the scan tool Top Closed Limit Switch parameter is Inactive.
    4. ⇒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.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the ignition circuit terminal B. Verify the scan tool Top Closed Limit Switch parameter is Active.
    5. ⇒If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the FTC module.
  5. If all circuits test normal, test or replace the top closed switch.

Valve 1 Test

  1. Ignition OFF, wait four minutes for the module to release the pressure in the hydraulic system.
  2. Turn the hydraulic fluid by-pass valve counterclockwise to inhibit folding top movement.
  3. Ignition OFF, disconnect the X431 inline harness connector at the folding top motor assembly.
  4. Test for less than 5 ohms between the ground circuit terminal A2 and ground.
    5. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  5. Connect a test lamp between the control circuit terminal A5 and the ground circuit terminal A2.
  6. Ignition ON, command the Valve 1 ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    7. ⇒If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the module.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the FTC module.
  7. If all circuits test normal, replace the folding top motor assembly.

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 that a test lamp illuminates between the ignition circuit terminal B and ground.
    3. ⇒If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all switch signal circuits associated to the fuse for a short to ground.
  3. Verify the scan tool Tonneau Open Limit Switch parameter is Inactive.
    4. ⇒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.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the ignition circuit terminal B. Verify the scan tool Tonneau Open Limit Switch parameter is Active.
    5. ⇒If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the FTC module.
  5. If all circuits test normal, test or replace the folding top cover open switch.

Top Open Switch Test

  1. Ignition OFF, disconnect the harness connector at the top open switch.
  2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B and ground.
    3. ⇒If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.
  3. Verify the scan tool Top Open Limit Switch parameter is Inactive.
    4. ⇒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.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the ignition circuit terminal B. Verify the scan tool Top Open Limit Switch parameter is Active.
    5. ⇒If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the FTC module.
  5. If all circuits test normal, test or replace the top open switch.

Folding Top Cover Pull Down Ajar Test

  1. Open the folding top cover. If needed use manual operation.
  2. Ignition OFF, disconnect the harness connector at the folding top cover pull down actuator.
  3. Test for less than 5 ohms between the ground circuit terminal D and ground.
    4. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Power Pull Down Ajar Status parameter is Closed.
    5. ⇒If not the specified value, test the signal circuit terminal E for a short to ground. If the circuit tests normal, replace the BCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal E and the ground circuit terminal D. Verify the scan tool Power Pull Down Ajar Status parameter is Ajar.
    6. ⇒If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, replace the folding top cover pull down actuator.

Component Testing

Top Open Switch, Top Closed Switch, or 5 Bow Raised Switch

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Folding Top Pump with Motor Replacement
    •  Folding Top Stowage Compartment Lid Latch Striker Replacement
    •  Folding Top Cylinder Replacement
    •  Folding Top Position Switch Replacement - Number 5 Bow
    •  Control Module References for FTC module and BCM replacement, setup, and programming