GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Uplander 🢒 Brakes 🢒 Park Brake 🢒 DTC B1420

Circuit Description

The body control module (BCM) provides a 12 volt reference voltage for the ignition switch.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1420 Device Voltage

Conditions for Running the DTC

The voltage supplied to the BCM is in the range of 9-16 volts.

Conditions for Setting the DTC
    • The BCM senses a short to ground in the 12 volt reference circuit.
    • The above condition lasts for at least 1 second.

Action Taken When the DTC sets
    • The BCM will disable the output for the rest of the ignition cycle.
    • The setting of this DTC inhibits the setting of other DTCs.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the ignition has been cycled 100 times, without a repeat of the malfunction.

Diagnostic Aids
    • The following may cause an intermittent:
       - A damaged terminal
       - A backed out terminal
       - A poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
    • When diagnosing an intermittent short or an open, manipulate the wire harness while watching the test equipment for changes.

Step

Action

Yes

No

Schematic Reference: Body Control System Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to in Vehicle DTC Information

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Retrieve DTCs from body control module (BCM).

Is the DTC set as current?

Go to Step 3

Go to Diagnostic Aids

3
  1. Turn OFF the ignition.
  2. Disconnect the BCM connectors.
  3. Test the 12 volt reference circuit at the BCM connector 1 for a short to ground.
  4. Refer to the following in Wiring Systems:

Did you find and correct the condition?

Go to Step 9

Go to Step 4

4
  1. Test the Ignition 1 voltage circuit for a short to ground.
  2. Refer to the following in Wiring Systems:

Did you find and correct the condition?

Go to Step 9

Go to Step 5

5
  1. Test the Ignition 3 voltage circuit for a short to ground.
  2. Refer to the following in Wiring Systems:

Did you find and correct the condition?

Go to Step 9

Go to Step 6

6
  1. Test the crank voltage circuit for a short to ground.
  2. Refer to the following in Wiring Systems:

Did you find and correct the condition?

Go to Step 9

Go to Step 7

7

Inspect for poor connections at the harness connectors of the BCM . Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 8

8

Replace the BCM . Refer to for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 9

--

9
  1. Reconnect all of the disconnected modules.
  2. Use the scan tool in order to clear the DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK