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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 >> DTC B0004 >> 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 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.
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