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Home >> Isuzu >> 2007 >> Ascender 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 439 (Cellular System, Entertainment System & Navigation System) >> Diagnostic Information and Procedures >> Navigation System - Vehicle Position Indicator Inoperative or Erratic >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Envoy and 2009 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT: Diagnose any antilock brake system (ABS) related DTCs before performing this diagnostic.
  1. Ignition OFF, disconnect the radio harness connector X4. Connect a DMM to the vehicle speed signal (VSS) circuit terminal 5 and ground.
  2. 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 EBCM.
  3. If the circuit tests normal, replace the radio.
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