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).
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B0004 Vehicle Speed Information Circuit Open
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. |
Diagnostic Aids
An intermittent condition may be caused by the following:
| • | Mis-routed harness |
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
| • | A loose connector pin |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the malfunction is present.
-
This step tests for an open in the vehicle speed signal circuit between the IPC and the navigation radio. A short would cause the IPC to malfunction as well as the navigation system.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Navigation System Schematics | |||
Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go Diagnostic System Check - Vehicle in Vehicle DTC Information | |
2 | Verify the instrument panel cluster (IPC) speedometer operation. Does the speedometer work on the IPC? | Go to Step 3 | Go to Diagnostic Starting Point - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console |
Test the vehicle speed signal circuit for an open between the IPC and the navigation radio. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 | |
4 | Inspect for poor connections at the harness connector of the navigation radio. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 | Replace the navigation radio. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
