Steering Wheel Controls Inoperative. Isuzu Ascender

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2007 🢒 Ascender - 2WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Steering Wheel Controls Inoperative

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.

The body control module (BCM) supplies voltage to the audio steering wheel control multiple momentary contact switches and monitors the return signal. Each switch is associated to a set resistance value, when pressed a specific voltage drop occurs through a series of resistors unique to that switch. The BCM identifies the selection, then sends a serial data message that is received by the component controlled, activating the feature.

Diagnostic Aids

•	This diagnostic is for the audio steering wheel controls.

•	Before diagnosis of the steering wheel controls, ensure the primary controls of the associated component are functioning properly.

•	Review with the schematic when testing switch resistance values.

•	If a single switch function is inoperative, test the suspect switch. Refer to component testing.

•	A poor connection at the right switch could cause the left switch to malfunction or be inoperative.

Reference Information

Schematic Reference

Steering Wheel Secondary/Configurable Control Schematics

Connector End View Reference

•	Secondary/Configurable Control Connector End Views

•	Data Communication Connector End Views

Description and Operation

Steering Wheel Controls Description and Operation

Electrical Information Reference

•	Circuit Testing

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

•	Connector Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Verification

Ignition ON, observe the scan tool steering wheel controls (SWC) Switch Voltage parameter in the BCM data list . Pressing the switch should read voltage present, and drop to 0 volt when released.

Circuit/System Testing

Important: It is recommended that Component Testing is performed before Circuit Testing when diagnosing steering wheel controls.

Caution: Refer to SIR Caution in the Preface section.

Ignition OFF, disconnect the harness connector at the right steering wheel control switch.
Ignition ON, test for ignition voltage between the ignition circuit terminal 1 and ground.

⇒	If less than the specified value, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

Test for ignition voltage between the ignition circuit terminal 1 and the signal circuit terminal 6.

⇒	If less than the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

⇒	If greater than the specified value, test the signal circuit for a short to voltage.

Install a 3A fused jumper wire at the ignition circuit terminal 1 and the ignition circuit jumper terminal 2.
Disconnect the harness connector at the left steering wheel control switch.
Test for ignition voltage between the ignition circuit jumper terminal 1 and ground.

⇒	If less than the specified value, test the signal circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the BCM.

Test for ignition voltage between the ignition circuit jumper terminal 1 and the signal circuit terminal 5.

⇒	If less than the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

Disconnect the harness connector C1 at the BCM.
Test for infinite resistance between the signal circuit terminal B8 and ground.

⇒	If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.

If all circuits test normal, test or replace the switch.

Component Testing