GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC B1438

Circuit Description

The instrument cluster (IPC) supplies 54 volts to the instrument panel integration module (IPM) for operation of the HVAC vacuum fluorescent (VF) display. The IPC performs a diagnostic test on the 54V VF display supply every 100 milliseconds.

Conditions for Running the DTC
    • The battery voltage is greater than 9 volts.
    • The 54V VF display supply is active.

Conditions for Setting the DTC

The current draw by the IPM on the 54V VF display supply circuit is greater than 100 milliamps for 5 diagnostic tests.

Action Taken When the DTC Sets
    • For 2.5 seconds, the IPC enters recovery diagnostic mode. The IPC continues to check the circuit for a reduction in current draw.
    • After 2.5 seconds, the IPC disables the 54V VF display supply.

Conditions for Clearing the DTC
    • Current DTC
       - During the recovery diagnostic mode, the current draw by the IPM on the 54V VF display supply circuit is less than 95 milliamps for 5 diagnostic tests.
       - The ignition is OFF.
    • History DTC
       - A scan tool is used.
       - The IPC automatically clears the history DTC when a current DTC is not detected for 50 consecutive ignition cycles.

Diagnostic Aids
    • An intermittent condition can be caused by the following:
       - The wiring harness is routed incorrectly.
       - The insulation of the wiring is rubbed through.
    • Following successful diagnosis, cycle the ignition so that initialization of the circuit occurs.

Step

Action

Yes

No

Schematic Reference: Interior Lights Dimming Schematics

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. Turn OFF the ignition.
  5. Disconnect the instrument panel integration module (IPM).
  6. Turn ON the ignition, with the engine OFF.
  7. Select the display DTCs function on the scan tool for the instrument cluster (IPC).

Does the scan tool display DTC B1438 for the instrument cluster (IPC) as current?

Go to Step 3

Go to Step 5

3

Test the 54V VF display supply circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 4

4

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

Did you find and correct the condition?

Go to Step 8

Go to Step 6

5

Inspect for poor connections at the harness connector of the instrument panel integration module (IPM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Replace the instrument cluster (IPC). Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.

Did you complete the replacement?

Go to Step 8

--

7

Important:: Perform the setup procedure for the Instrument Panel Integration Module (IPM). Refer to Body Control Module (BCM) Programming/RPO Configuration .

Replace the IPM. Refer to Instrument Panel Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 8

--

8
  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