GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) applies battery voltage to the accessory voltage circuit when the ignition is in the ON position. The folding top control (FTC) module monitors this circuit at least once every 300 milliseconds to determine if voltage is supplied to the following folding top switches:

    • Top open switch
    • Top closed switch
    • Luggage barrier switch
    • Folding top cover open switch
    • 5 bow raised switch
    • 5 bow lowered switch
    • Pin receiver switch

DTC Descriptor

The diagnostic procedure supports the following DTC:

DTC B1420 Device Voltage

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

    • If the FTC module detects the accessory voltage dropping 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.
    • History and current DTC can be cleared using the scan tool.

Step

Action

Values

Yes

No

Schematic Reference: Folding Top Schematics

Connector End View Reference: Folding Top Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Diagnostic Trouble Codes (DTC) in the Folding Top Module data list.

Is DTC B1420 present?

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Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

Measure the accessory voltage at the FTC module harness connector.

Does the voltage measure near the specified value?

9-16 V

Go to Step 5

Go to Step 4

4

  1. Install and secure the cargo cover to close the luggage barrier limit switch.
  2. With a scan tool, observe the Luggage Barrier In Place parameter in the Folding Top Module Input data list.

Does the scan tool display Yes?

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Go to Step 6

Go to Step 7

5

Inspect for poor connections at the harness connector of the folding top control (FTC) module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs.

Did you find and correct the condition?

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Go to Step 9

Go to Step 8

6

Repair the high resistance or open in the accessory voltage circuit between the FTC module and the splice. Refer to Circuit Testing and to Wiring Repairs.

Did you complete the repair?

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Go to Step 9

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7

Repair the short to ground or open in the accessory voltage circuit of the FTC module. Refer to Circuit Testing and to Wiring Repairs.

Did you complete the repair?

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Go to Step 9

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8

Replace the FTC module. Refer to Control Module References for replacement, setup, and programming .

Did you complete the replacement?

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Go to Step 9

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9

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

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Go to Step 2

System OK