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Test TJ: Output Shaft Speed Sensor: Testing

    NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  1. 1) For Continuous Memory Only DTCs P0720, P0721, P0722, P0723 & P1900: Verify Drive Cycle
    DTC P0720 is set when PCM detects insufficient input signal from OSS sensor. DTC P0721 is set when PCM detects noise interference on OSS sensor signal. DTC P0722 is set when PCM detects missing OSS sensor signal. DTCs P0723 and P1900 are set when PCM detects irregular or interrupted OSS sensor signal. Possible causes are:
    • OSS Sensor Circuit Open, or Shorted To GND or PWR
    • Wiring Misrouted, Damaged Or Insulation Worn
    • After Market Add-On
    • Harness Intermittently Shorted Or Open, Connector Damaged Or Not Properly Seated
    • Faulty Or Incorrectly Installed OSS Sensor
    • Faulty PCM

    Using scan tool, access OSS PID from PID/DATA MONITOR & RECORD menu. Road test vehicle and observe OSS PID. Ensure transmission shifts through all gear ranges, up and down. If OSS PID value increases and decreases with engine and vehicle speed, go to next step. If OSS PID value does not increase and decrease with engine and vehicle speed, perform the following:

    • On Focus 2.0L M/T, go to step  3).
    • On all others, go to step  5).

  2. 2) Visual Inspection

    Turn ignition switch to OFF position. Disconnect OSS sensor connector located on side of transmission. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. If connector is okay, fault is unable to be duplicated at this time. Go to TEST Z, step  1) and check for intermittent faults.

  3. 3) Check VPWR To OSS Sensor

    Turn ignition switch to OFF position. Disconnect OSS sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and VPWR circuit at OSS sensor harness connector. See Figure. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in OSS circuit.

  4. 4) Check PWR GND To OSS Sensor

    Ensure ignition switch is turned to OFF position. Using a DVOM, measure resistance between negative battery terminal and PWR GND circuit at OSS sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in PWR GND circuit.

  5. 5) Check OSS Circuit For Short To VPWR

    Disconnect OSS sensor connector, if not done previously. Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal and OSS circuit at OSS sensor harness connector. See Figure-Figure . If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to VPWR in OSS circuit.

  6. 6) Check OSS & SIG RTN Circuits For Open In Harness

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of OSS and SIG RTN circuits between PCM harness connector and OSS sensor harness connector. If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open in OSS or SIG RTN circuit.

  7. 7) Check OSS Circuit For Short To SIG RTN Circuit Or Chassis Ground

    Using a DVOM, measure resistance between OSS circuit, and SIG RTN circuit at OSS sensor harness connector and chassis ground. If either resistance measurement is 10 k/ohms or less, repair OSS circuit for short to chassis ground or SIG RTN circuit. If both resistance measurements are more than 10 k/ohms, perform the following:
    • On Focus 2.0L M/T, go to step  9).
    • On all others, go to next step.

  8. 8) Check Resistance Of OSS Sensor

    Using a DVOM, measure resistance between OSS sensor terminals. If resistance is 450-1250 ohms, replace PCM. If resistance is not 450-1250 ohms, replace OSS sensor.

  9. 9) Check OSS Signal Output To PCM (3-Wire OSS Sensor)

    Raise and support front of vehicle so that front wheels can rotate freely. Turn ignition switch to ON position and place gearshift lever in Neutral. Using a DVOM, measure voltage between OSS and PWR GND circuits at PCM harness connector while rotating one wheel with opposite wheel held stationary. See Figure. If OSS sensor output voltage pulses from less than one volt to more than 5 volts, replace PCM. If voltage does not pulse as specified, replace OSS sensor.
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