Diagnostic Instructions
DTC Descriptor
DTC B1372 : Device Ignition 1 (ON and START) Circuit Low
Circuit Description
When the ignition switch is in the UNLOCK position, certain class 2 messages do not transmit. The instrument cluster suspends the operation of the indicators and the gages that are dependent on these messages until the ignition switch is no
longer in the UNLOCK position.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
There is a difference of at least 8 volts between the ignition 1 voltage circuit and the battery positive voltage for 3 seconds. The instrument panel cluster (IPC) receives a class 2 message indicating the battery voltage and
compares this to the ignition 1 voltage.
Action Taken When the DTC Sets
| • | The odometer and the PRNDL displays do not illuminate. |
| • | The fuel gage and the engine coolant temperature gage default to 0. |
| • | The scan tool does not communicate with the instrument cluster. |
Conditions for Clearing the DTC
| • | The DTC becomes history when the difference between the ignition 1 voltage and the battery voltage is only 3 volts for 3 seconds. |
| • | The history DTC clears after 100 malfunction free warm-up cycles. |
| • | The IPC receives the clear code command from the scan tool. |
Diagnostic Aids
| • | When the IPC detects low voltage at the ignition 1 voltage circuit, the instrument cluster will not communicate with the scan tool, and the odometer and PRNDL displays will not be illuminated. The season odometer will display if the trip reset switch
is pressed, and the instrument cluster will communicate with the scan tool until the trip reset switch is released. |
| • | An intermittent condition is likely to be caused by an open condition in the ignition 1 voltage circuit. |
| • | DTC B1372 can only be read by the scan tool as a history code once the fault is removed. Refer to
Control Module References in Computer/Integrating Systems. |
Reference Information
Schematic Reference
Instrument Cluster Schematics
Connector End View Reference
Instrument Panel, Gages, and Console Connector End Views
Description and Operation
Instrument Cluster Description and Operation
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the IPC.
- Ignition ON, verify that a test lamp illuminates between the battery positive voltage and ground
| ⇒ | If the test lamp does not illuminate, repair the battery positive voltage circuit for a short to ground or an open/high resistance. |
- Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit and ground
| ⇒ | If the test lamp does not illuminate, repair the ignition 1 voltage circuit for a short to ground or an open/high resistance. |
- If all circuits test normal, test or replace the IPC.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the IPC replacement, setup, and programming
