GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 PJJ 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC B1372 Device Ignition 1 (ON/START) Circuit Low

Object Number: 491050 Size: SF
Body Control Module Components
Powers, Grounds and Class 2 Data Lines

Circuit Description

Circuit 39 is the ignition 1 positive voltage circuit input to the body control module (BCM) and the instrument panel cluster (IPC) from the ignition switch. When the BCM senses that ignition 1 is open or shorted to ground, DTC B1372 is set.

Conditions for Running the DTC

The ignition switch is on.

Conditions for Setting the DTC

The ignition 1 input is not active for 30 seconds.

Action Taken When the DTC Sets

The BCM stores DTC B1372 in memory.

Conditions for Clearing the DTC
    • DTC B1372 will clear when the code setting condition is no longer present.
    • All BCM history codes will clear after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.

Diagnostic Aids

If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while wiggling the wiring and connectors. This can often cause the malfunction to appear.

Test Description

The numbers listed below refer to the numbers on the diagnostic table.

  1. This step determines if CKT 39 is shorted to ground.

    2.

  2. This step determines if the BCM is internally shorted.

    3.

  3. This step determines if the instrument cluster is internally shorted.

    4.

  4. This step determines if voltage is supplied from the battery to the BCM/CLSTR fuse.

Step

Action

Yes

No

1

Did you perform the Body Control System Diagnostic System Check?

Go to Step 2

Go to A Diagnostic System Check - Body Control System

2
  1. Install a Scan Tool.
  2. Turn ON the ignition, leaving the engine OFF.
  3. With the Scan Tool, observe the IGNITION 1 input parameter in the BCM data list.

Does the scan tool display ON?

Go to Testing for Intermittent and Poor Connections in Wiring Systems

Go to Step 3

3

Inspect the BCM/CLU fuse.

Is the fuse open?

Go to Step 4

Go to Step 7

4
  1. Connect a test lamp between the BCM/CLU fuse terminals at the IP fuse block.
  2. Turn ON the ignition, leaving the engine OFF.

Does the test lamp illuminate?

Go to Step 5

Go to Testing for Intermittent and Poor Connections in Wiring Systems

5
  1. Turn OFF the ignition.
  2. Disconnect the BCM connector C3.
  3. Turn ON the ignition, leaving the engine OFF.

Does the test lamp still illuminate?

Go to Step 6

Go to Step 11

6
  1. Turn OFF the ignition.
  2. Disconnect the IPC connector.
  3. Turn ON the ignition, leaving the engine OFF.

Does the test lamp still illuminate?

Go to Step 9

Go to Step 12

7
  1. Remove the BCM/CLU fuse.
  2. Turn ON the ignition, leaving the engine OFF.
  3. Probe both fuse terminals for the ignition 1 positive voltage circuit at the IP fuse block with a test lamp connected to ground.

Does the test lamp illuminate for one of the terminals?

Go to Step 8

Go to Step 10

8

Test the ignition 1 positive voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

9

Repair the short to ground in the ignition 1 positive voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the action?

Go to Step 15

--

10

Repair the open in the ignition feed circuit to the BCM/CLSTR fuse. Refer to Wiring Repairs in Wiring Systems.

Did you complete the action?

Go to Step 15

--

11

Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

12

Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

13

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Important: Perform the setup procedure for the BCM. Refer to BCM Programming/RPO Configuration.

Is the repair complete?

Go to Step 15

--

14

Replace the IPC. Refer to IP Cluster Replacement in Instrument Panel, Gauges and Console.

Is the repair complete?

Go to Step 15

--

15
  1. Use the Scan Tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK