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 Descriptors

DTC B1420: Device Voltage

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

When the ignition is in the ON position, battery voltage from the auxiliary relay is applied through the 15-amp FOLDING TOP/TRUNK LATCH fuse and the control circuit to the folding top control (FTC) module. The FTC module monitors this circuit at least once every 300 milliseconds to determine if voltage is supplied to the following folding top switches:

    • Front latched switch
    • Front unlatched switch
    • Compartment partition switch
    • Rear compartment lid open switch or deck lid open switch
    • Folding top closed switch
    • Rear compartment lid pulldown actuator

Conditions for Running the DTC

The battery voltage is between 9-16 volts.

Conditions for Setting the DTC

    • The FTC module detects the control circuit voltage dropped below 3 volts.
    • The power mode is either in Accessory, RUN, Rap or Crank.

Action Taken When the DTC Sets

    • Stores a current and history DTC B1420 in the FTC module.
    • The folding top operation is suspended.
    • If the condition occurs during operation of the folding top, once the top control switch is released, the FTC module will send a class 2 message to the driver information center (DIC), displaying 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.

Diagnostic Aids

The Rear Compartment Lid is also referenced as the Deck Lid for this vehicle.

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 Testing

  1. Ignition OFF, disconnect the X2 harness connector at the FTC module.
  2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal D11 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. If all circuits test normal, replace the FTC module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for FTC module replacement, setup, and programming