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




Circuit Description

The navigation radio receives the vehicle speed signal from the powertrain control module (PCM) through a dedicated circuit shared with the instrument panel cluster (IPC).


Conditions for Running the DTC

* The navigation radio must detect a power mode transition to ON.
* The radio does not set this DTC if B1327 or B1328 is current.
* 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 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 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 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 PCM 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 (Component Connector End Views)
Description and Operation

OnStar Description and Operation (OnStar Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning)for scan tool information


Diagnostic Aids

A short to voltage or ground in the vehicle speed circuit will cause an instrument panel cluster (IPC) speedometer problem also. Make sure there are no IPC speedometer concerns.


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector X2 at the radio. Disconnect the harness connector X1 at the instrument panel cluster.
2. Test for less than 5 ohms on the vehicle speed signal between the radio harness connector X2 terminal E and the IPC connector X1 terminal 21

• If less than the specified range, repair the open/high resistance. If the circuit tests normal, replace the radio.




Repair Instructions

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

* Inside Rearview Mirror Replacement (Inside Rearview Mirror Replacement)
* Programming and Relearning (Programming and Relearning)for radio replacement, setup, and programming