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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 141 (Engine Controls Self-Diagnostics - 5.7L - Bi-Fuel) >> Diagnostic Tests >> DTC P0500: VSS Circuit >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Using the scan tool, establish communication with the PCM. Inspect for DTC P0608. Is DTC P0608 stored as History? If yes, diagnose this DTC first. See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If no, go to next step.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition? If yes, go to step  5 . If no, go to next step.
  4. The fault is not present. See DIAGNOSTIC AIDS  . Are any DTCs stored that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  5. Test the vehicle speed output circuit for an open condition between the circuit splice and the AF ECM connector. Inspect the AF ECM connector for poor terminal contact. Repair circuit or terminal contact as necessary. Was a circuit or terminal repair made? If yes, go to step  7 . If no, go to next step.
  6. Replace AF ECM. See ALTERNATE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CHEVY EXPRESS & SAVANA - BI-FUEL. Program (flash) AF ECM with correct vehicle software and calibration. See ALTERNATE FUEL ENGINE CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  7. Reconnect all disconnect or removed components, connectors, fuses, etc. Using a scan tool, clear all DTC information from BOTH the PCM and the AF ECM. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running DTC until the scan tool indicates the diagnostic ran. Does the scan tool indicate the DTC passed? If yes, system is okay. If no, go to step  2 .
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