For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Circuit/System Description

With the headlight switch in the HEADLAMP or PARKLAMP position, the appropriate headlamp switch signal circuit is grounded through the headlight switch. The body control module (BCM) then sends a serial data message to the instrument cluster requesting the instrument cluster to illuminate the lights on indicator. With the turn signal/multifunction switch in the HIGH BEAM or FLASH TO PASS position the appropriate turn signal/multifunction switch signal circuit is grounded through the turn signal/multifunction switch. The BCM then sends a serial data message to the instrument cluster requesting the instrument cluster to illuminate the high beam indicator. The BCM will also request the instrument cluster to turn on the lights on indicator located in the driver information center anytime the headlamps are ON and the ignition is OFF or the driver door is opened.

### Diagnostic Aids

This diagnostic procedure assumes that the headlamps operate as described in Exterior Lighting Systems Description and Operation.

### Reference Information

#### Schematic Reference

• | Instrument Cluster Schematics

• | Exterior Lights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior Lighting Systems Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

#### Lights On Indicator Malfunction

Ignition ON, command the All Indicators test ON and OFF with the scan tool, verify that the lights on indicator changes between turn ON and OFF.

⇒ | If the lights on indicator does not illuminate during the test or remains illuminated at all times, replace the P16 Instrument Cluster.

⇒ | If the lights on indicator illuminates during the test, replace the K9 Body Control Module (BCM).

#### High Beam Indicator Malfunction

Ignition ON, command the All Indicators test ON and OFF with the scan tool, verify that the high beam indicator changes between turn ON and OFF.

⇒ | If the high beam indicator does not illuminate during the test or remains illuminated at all times, replace the P16 Instrument Cluster.

⇒ | If the high beam indicator illuminates during the test, replace the K9 Body Control Module (BCM).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM or instrument cluster replacement, setup, and programming