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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) For Continuous Memory Only DTCs P0500, P0501 & 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. 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.

    This test step checks for recurrence of this vehicle speed error. Turn ignition switch to ON position. Connect scan tool to Data Link Connector (DLC). Clear all DTCs. Obeying all local traffic laws, complete the following drive cycle:

    • Take the vehicle to a suitable location and gradually increase the vehicle speed to 50 MPH.
    • Coast down to an idle and stop the vehicle.
    • Shut the engine off.
    • After the drive cycle is completed, retrieve any Continuous Memory DTCs.

    If DTC P0500, P0501 or P1502 is present, turn ignition switch to OFF position. Vehicle speed input was not as expected, go to next step. If DTC P0500, P0501 or P1502 is not present, turn ignition off. Vehicle speed input was as expected, fault that produced original DTC may be intermittent. Go to step  5).

  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. Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal, and VSC GND, and 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 WIRING DIAGRAMS . 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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