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  • P0720 Low Output Speed Sensor RPM Above 15 MPH

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    Mopar1973Man

    DTC P0720: LOW OUTPUT SPEED SENSOR RPM ABOVE 15 MPH

    Circuit Description

    Circuit is monitored continuously while ignition is on and gearshift lever is not in Park or Neutral. DTC sets if vehicle speed is above 15 MPH and output shaft speed is less than 60 RPM for 2.6 seconds as measured from vehicle speed signal.

    Possible Cause

    • Open output speed sensor ground circuit.
    • Damaged ignition wiring.
    • Open output speed sensor signal circuit.
    • Short to ground in output speed sensor signal circuit.
    • Park/Neutral switch DTC present.
    • Malfunctioning sensor.
    • Short to ground in output speed sensor ground circuit.
    • Malfunctioning PCM.
    • Output speed sensor harness intermittent fault.

    Diagnostic Procedure

    1. Using scan tool, read DTCs. If good trip counter for DTC P0720 is not displayed or displayed count is not zero, go to step 10 . If good trip counter is displayed and displayed count is zero, go to next step.

    2. Record all DTCs and one trip failures. If DTC P1899 is present, repair P/N switch DTC first. See DTC P1899: P/N SWITCH STUCK IN PARK OR IN GEAR (DIESEL) or DTC P1899: P/N PERFORMANCE (GASOLINE) . If DTC P1899 is not present, go to next step.

    3. Turn ignition off. Disconnect PCM harness connectors and output speed sensor harness connector. sensor ground circuit between appropriate output speed sensor harness connector terminal and appropriate PCM harness connector C2 (White) terminal. See WIRING DIAGRAMS . If resistance is 5 ohms or more, repair output speed sensor ground circuit for open. If resistance is less than 5 ohms, go to next step.

    4. Measure resistance between ground and output speed sensor ground circuit at appropriate PCM harness connector C2 (White) terminal. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair output speed sensor ground circuit for short to ground.

    5. Measure resistance between ground and output speed sensor signal circuit at appropriate PCM harness connector C2 (White) terminal. If resistance is less than 5 ohms, repair output speed sensor signal circuit for short to ground. If resistance is 5 ohms or more, go to next step.

    6. Measure resistance of output speed sensor signal circuit between appropriate output speed sensor harness connector terminal and appropriate PCM harness connector C2 (White) terminal. If resistance is 5 ohms or more, repair output speed sensor signal circuit for open. If resistance is less than 5 ohms, go to next step.

    7. Turn ignition on. Measure voltage of output speed sensor ground circuit at appropriate output speed sensor harness connector terminal. If any voltage is present, repair output speed sensor ground circuit for short to voltage. If no voltage is present, go to next step.

    8. Measure voltage of output speed sensor signal circuit at appropriate output speed sensor harness connector terminal. If any voltage is present, repair output speed sensor signal circuit for short to voltage. If no voltage is present, go to next step.

    9. Turn ignition off. Measure resistance between output speed sensor terminals. If resistance is 300-1200 ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. If resistance is not 300-1200 ohms, replace output speed sensor. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS.

    10. Conditions required to set DTC are not currently present. Inspect all applicable connectors and terminals for damage. Repair as necessary. If connectors and terminals are okay, see INACTIVE DTC CONDITION under SELF-DIAGNOSTIC SYSTEM. Testing is complete.



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