DTC B0540. Isuzu Ascender

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2007 🢒 Ascender - 2WD 🢒 Driver Information and Entertainment 🢒 Displays and Gages 🢒 DTC B0540

Diagnostic Instructions

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

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

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

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Vehicle Speed Signal Circuit	B0540	B0540	B0540	--

The instrument panel cluster (IPC) receives the vehicle speed information from the engine control module (ECM)/powertrain control module (PCM) through the vehicle speed signal circuit. The ECM/PCM converts the data from the vehicle speed sensor to a 4000 pulses/mile signal. The ECM/PCM also sends a class 2 message to the IPC indicating the vehicle speed. If the IPC determines there is a loss of the vehicle speed signal from the ECM/PCM due to a vehicle speed signal circuit malfunction, a DTC sets.

Conditions for Running the DTC

•	The vehicle speed is more than 10 km/h (6 mph).

•	The ignition voltage is between 9-18 volts.

Conditions for Setting the DTC

•	The IPC detects that the vehicle speed signal circuit does not match the vehicle speed from the class 2 serial data circuit.

•	The condition above must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

•	The IPC stores a DTC B0540 in memory.

•	The speedometer defaults to 0 km/h (0 mph).

•	No driver warning message will be displayed for this DTC.

Conditions for Clearing the DTC

•	The history DTC clears after 100 malfunction-free warm-up cycles.

•	The DTC becomes history when the conditions for setting the DTC are no longer present.

•	The IPC receives the clear code command from the scan tool.

Reference Information

Schematic Reference

•	Instrument Cluster Schematics

•	Engine Controls Schematics for the 4.2L engine

•	Engine Controls Schematics for the 5.3L engine

•	Engine Controls Schematics for the 6.0L engine

Connector End View Reference

•	Displays and Gages Connector End Views

•	Powertrain Control Module Connector End Views

•	Engine Control Module Connector End Views for the 5.3L engine

•	Engine Control Module Connector End Views for the 6.0L engine

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the ECM/PCM. Install a signal generator and instrument panel tester between the vehicle speed signal circuit and ground.
Ignition ON, set the signal generator to generate a speedometer signal. Verify that the vehicle speedometer indicates a reading.

⇒	If no speedometer reading is present, test the signal circuit for an open/high resistance, a short to voltage, or a short to ground. If the circuit tests normal, replace the IPC.

If all circuits test normal, test or replace the ECM/PCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM/PCM and IPC replacement, setup, and programming