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. |
Circuit Description
The radio receives a vehicle speed signal from the electronic brake control module (EBCM) in order to correlate actual vehicle speed to the movement of the vehicle calculated by the navigation system and reported serial data. The vehicle speed signal also serves the purpose of updating the vehicle position indicator on the navigation screen.
Reference Information
Schematic Reference
Radio/Navigation System Schematics
Connector End View Reference
Description and Operation
Navigation System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Radio ON, switch to the navigation screen on the radio. Drive the vehicle greater than 15 mph. Verify that the navigation screen shows that the vehicle is moving.
Circuit/System Testing
Important: Diagnose any antilock brake system (ABS) related DTCs before performing this diagnostic.
- Ignition OFF, disconnect the radio harness connector X4. Connect a DMM to the vehicle speed signal (VSS) circuit terminal 5 and ground..
- Ignition ON, operate the vehicle drive wheels at 5 mph. Verify 3-7 Hertz on the VSS circuit.
- If the circuit tests normal, replace the radio.
| ⇒ | 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 EBCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
See Control Module References for Radio replacement, setup, and programming
