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Test DF: Vehicle Speed Circuit Check: Testing

NOTE: Proceed to DTC testing steps listed in FAULT CODE SETTING CONDITION  table of fault code setting condition.
FAULT CODE SETTING CONDITION

Fault Code KOEO KOER Continuous Memory
P0500      DF1
P0501      DF1
    NOTE: For additional testing information, see DIAGNOSTIC AIDS .
    NOTE: On most vehicles, DTC P0500 will cause Malfunction Indicator Light (MIL) to illuminate. When DTC P0501 is set, MIL will not be illuminated. When DTC P1502 is set, Transmission Control Indicator Light (TCIL) will flash with the first VSS circuit malfunction.

  1. 1) Continuous Memory DTC P0500, P0501 Or P1502: Check Vehicle Speed PID
    DTCs P0500, P0501 and P1502 indicate that PCM has detected an error in vehicle speed information received from Vehicle Speed Sensor (VSS), Transfer Case Speed Sensor (TCSS) or Anti-Lock Brake System (ABS) module. See VEHICLE SPEED CIRCUIT MODULE IDENTIFICATION  table. Possible causes for this fault are:
    • Open or short in VSS (+) or VSS (-) circuit.
    • Open in TCSS signal or TCSS signal return circuit.
    • Short to GND in VSS or TCSS circuit.
    • Short to PWR in VSS or TCSS circuit.
    • Open or short in VSC between PCM and appropriate control module.
    • Faulty wheel speed sensor(s).
    • Faulty wheel speed sensor(s) wiring harness.
    • Faulty module(s) connected to vehicle speed circuit.
    • Faulty transfer case, vehicle or wheel speed sensors.
    • Faulty drive mechanism for VSS or TCSS.
    VEHICLE SPEED CIRCUIT MODULE IDENTIFICATION

    Application (1) Module
    Excursion 5.4L & 6.8L 4-Wheel Anti-Lock Brake System (4WABS) Module
    Pickup 5.4L & 6.8L 4WABS Module, Or Rear Anti-Lock Brake System (RABS) Module
    (1) Module that is responsible for sending Vehicle Speed Circuit (VSC) signal to PCM.

    Turn ignition switch to ON position. Connect scan tool to Data Link Connector (DLC). Using scan tool, access VSS PID from PID/DATA MONITOR & RECORD menu. Road test vehicle and gradually accelerate vehicle to 50 MPH while observing VSS PID. If VSS PID value matches speedometer, fault is unable to be duplicated at this time. Go to step  5). If VSS PID value does not match speedometer, go to next step.

  2. 2) Check VSC For Short To Power In Harness

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Disconnect appropriate control module. See VEHICLE SPEED CIRCUIT MODULE IDENTIFICATION  table. Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal, and terminal No. 33 (VSC GND), and terminal No. 58 (VSC SIG) at PCM harness connector. If both voltages are less than one volt, go to next step. If either voltage is one volt or more, go to step  6).

  3. 3) Check For Open VSC Circuit Between PCM & ABS Control Module

    Turn ignition switch to OFF position. Using a DVOM, measure resistance of VSC SIG and VSC GND circuits between appropriate control module harness connector and PCM harness connector. If resistances are less than 5 ohms, go to next step. If either resistance is 5 ohms or more, repair open in affected circuit. After repair is complete, go to step  7) to perform VSC Repair Verification Drive Cycle.

  4. 4) Check VSC Circuit For Short To Ground In Harness

    Disconnect scan tool from Data Link Connector (DLC). Using a DVOM, measure resistance between VSC SIG circuit, VSC GND circuit at PCM harness connector and chassis ground. If any resistance measurement is 10 k/ohms or less, go to step  6). If all resistance measurements are more than 10 k/ohms, check for fault in ABS control module, speed sensors and speed sensor circuits. See appropriate ANTI-LOCK article in BRAKES. If no faults are present, replace PCM. After repair is complete, go to step  7) to perform VSC Repair Verification Drive Cycle.

  5. 5) Visual Inspection

    Turn ignition switch to OFF position. Visually inspect vehicle speed circuit wiring harness for any of the following conditions:
    • Loose or corroded connector at appropriate control module.
    • Loose or corroded PCM harness connector.
    • Incorrect wiring harness routing of vehicle speed circuits.

    If any faults are present, repair as necessary. After repair is complete, go to step  7) to perform VSC Repair Verification Drive Cycle. If no concerns are found, fault is intermittent. Check for intermittent fault in appropriate ABS system. See appropriate ANTI-LOCK article in BRAKES.

  6. 6) Check VSC Circuit For Short In Harness Or Another Module

    Determine if any other modules are connected to vehicle speed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If no other modules are connected to vehicle speed circuit, repair short in vehicle speed circuit and go to next step. If other modules are connected to vehicle speed circuit, disconnect one module at a time that are associated with vehicle speed circuit. Repeat step  2) or  4) (depending on which step directed you here) to determine if short still exists in vehicle speed circuit. Repeat appropriate step until each associated module has been disconnected or short circuit has been eliminated. When short circuit disappears, diagnose appropriate module or related system causing short by determining appropriate article to diagnose specific module or system. See appropriate MODULE COMMUNICATIONS NETWORK article. If short circuit still exists with all associated modules disconnected, repair short in vehicle speed circuit and go to next step.

  7. 7) VSC Repair Verification Drive Cycle

    Connect all disconnected components. Ensure engine is warmed to normal operating temperature. Perform the appropriate drive cycle 3 times:

    1. A/T Equipped Vehicles

      Place gear selector in Drive. Obey all local traffic laws and accelerate heavily to 35 MPH. Coast down to idle speed and stop vehicle.

    2. M/T Equipped Vehicles

      Accelerate and shift from first to second gear. Continue to accelerate moderately to 40 MPH. Coast down to idle speed and stop vehicle.

    After third drive cycle, perform QUICK TEST . If any Continuous Memory DTCs are present, go to appropriate system test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If Continuous Memory DTCs are not present, testing is complete.

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