Diagnostic Instructions

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B2580 01: High Beam Control Circuit Short to Battery

DTC B2580 02: High Beam Control Circuit Short to Ground

DTC B2580 04: High Beam Control Circuit Open

DTC B3650 08: High Beam Request Signal Circuit Performance - Signal Invalid

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
High Beam Control	B2580 02	B2580 04	B2580 01	--
High Beam Request Signal	--	--	--	B3650 08

Circuit/System Description

The headlamp high beam relay is supplied with battery voltage at all times. The turn signal / multifunction switch signal circuit is grounded by pressing the turn signal / multifunction switch. The body control module (BCM) energizes the headlamp high beam relay by applying ground to the headlamp high beam relay control circuit. When the headlamp high beam relay is energized, the relay switch contacts close and battery voltage is applied through the high beam lamp fuses to the high beam lamp supply voltage circuit which illuminates the high beam lamps.

Conditions for Running the DTC

B2580 01, B2580 02 or B2580 04

High beam lamps ON.

B3650 08

Low beam lamps ON.

Conditions for Setting the DTC

B2580 01

The BCM detects a short to voltage on the control circuit.

B2580 02

The BCM detects a short to ground on the control circuit.

B2580 04

The BCM detects an open control circuit.

B3650 08

The BCM reports stuck switch.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, perform the Highbeam Command test. The high beam lamps should be ON / OFF when changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the KR48 Headlamp High Beam Relay.
2. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
3. Command the high beam Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module (BCM).

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).

4. If all circuits test normal, replace the KR48 Headlamp High Beam Relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.