B1529

DTC B1405, B1529, or B257B

Diagnostic Instructions

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

DTC Descriptors
DTC B1405 02
- Control Module Voltage Reference Output 2 Circuit Short to Ground

DTC B1405 03
- Control Module Voltage Reference Output 2 Circuit Low Voltage

DTC B1405 07
- Control Module Voltage Reference Output 2 Circuit High Voltage

DTC B1529 03
- Control Module Voltage Reference Output 5 Circuit Low Voltage

DTC B1529 07
- Control Module Voltage Reference Output 5 Circuit High Voltage

DTC B257B 03
- Lighting Control Switch Signal Low Voltage

DTC B257B 07
- Lighting Control Switch Signal High Voltage

Diagnostic Fault Information





Circuit/System Description

The body control module (BCM) supplies battery positive voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage to the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

B1405 03, B1529 03, or B257B 03

The BCM detects less than 0.3 V on the dimmer switch signal circuit.

B1405 07, B1529 07, or B257B 07

The BCM detects a voltage greater than 12.2 V on dimmer switch signal circuit.

Action Taken When the DTC Sets

The BCM will not dim or illuminate any LED backlighting supplied by the backlight lamp control circuits.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive fault free ignition cycles have occurred.

Reference Information
Schematic Reference

* Interior Lights Dimming Schematics (Interior Lights Dimming Schematics)
* Steering Wheel Secondary/Configurable Control Schematics (Steering Wheel Secondary/Configurable Control Schematics)

Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Interior Lighting Systems Description and Operation (Interior Lighting Systems)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, headlamps ON, vary the interior backlight dimming from low to full bright by using the dimmer switch. The interior backlighting should start dim and then become full bright.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Test for less that 10 Ohms between the ground circuit terminal 6 and ground.

• If greater than the specified range, test the ground circuit for an open high/resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

4. Ignition ON, test for less than 0.3 V between signal circuit terminal 12 and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.

5. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the B+ circuit terminal 1. The interior backlighting should be dimmed.

• If the interior backlighting is not dimmed, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.

6. If all circuits test normal, test or replace the S30 headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, programming and setup