B0004

DTC B0004

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 Descriptor
DTC B0004 00
- Vehicle Speed Information Circuit Open

Diagnostic Fault Information





Circuit Description

The navigation radio receives the vehicle speed signal from the engine control module (ECM).

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 ECM to the GPS location signal every second. 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 ECM is unavailable.

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

* The vehicle icon may jump to different positions on the map screen.
* The vehicle icon, 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 ECM for more than 1 second.
* A history DTC clears after 50 ignition cycles without a vehicle speed signal failure.

Reference Information
Schematic Reference

Radio/Navigation System Schematics (Radio/Navigation System Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Navigation System Description and Operation (Navigation System Description and Operation)
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 Testing

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


1. Ignition OFF, disconnect the X2 harness connector at the radio.
2. Ignition ON, operate the vehicle drive wheels at 5 mph. Test for 3-7 Hertz between the VSS circuit terminal E and ground.

• 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 ECM.

3. If the circuit tests normal, replace the radio.

Repair Instructions

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

Control Module References (Programming and Relearning) for radio and ECM replacement, setup, and programming