DTC B0004. Isuzu Ascender

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2007 🢒 Ascender - 2WD 🢒 DTC 🢒 DTC B0004

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.

DTC Descriptor

DTC B0004 : Vehicle Speed Information Circuit Open

Circuit Description

The navigation radio receives the vehicle speed signal from the powertrain control module (PCM).

Conditions for Running the DTC

•	The navigation radio must detect a power mode transition to ON.

•	The vehicle must drive for 4 km (2.5 mi) after receiving a global positioning system (GPS) signal.

Conditions for Setting the DTC

The navigation radio compares the vehicle speed signal from the PCM to the GPS location signal. If the GPS signal indicates that the vehicle has traveled 4 km (2.5 mi) but no vehicle speed signal was received, the radio sets the DTC.

Action Taken When the DTC Sets

The navigation radio uses the GPS signal when the vehicle speed signal from the PCM is unavailable.

The following symptoms may happen if the vehicle speed signal from the PCM is unavailable:

•	The vehicle icon may jump to different positions on the map screen.

•	The current position marker may not move on the map screen while the vehicle is being driven.

•	The route guidance accuracy may be degraded.

Conditions for Clearing the DTC

•	A current DTC clears when the navigation radio detects the vehicle speed signal from the PCM.

•	A history DTC clears after 50 ignition cycles without a vehicle speed signal failure.

Reference Information

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

•	Scan Tool Data List

•	Scan Tool Data Definitions

Circuit/System Testing

Important: Diagnose any antilock brake system (ABS) related DTCs before performing this diagnostic.

Ignition OFF, disconnect the C2 harness connector at the radio. Connect a DMM to the vehicle speed signal (VSS) circuit terminal E and ground.
Ignition ON, operate the vehicle drive wheels at 5 mph. Verify 3-7 Hertz on the VSS circuit.

⇒	If the reading is not as specified, test the VSS circuit for an open, high resistance, short to ground or short to voltage. If the circuit tests normal replace the PCM.

If the circuit tests normal, replace the radio.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for radio and PCM replacement, setup, and programming