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Home >> Mercury >> 2008 >> Milan Base, 3.0 1, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1920 (Engine Controls - Pinpoint Test DL: Cylinder Head Temperature (CHT) Sensor Through Pinpoint Test DX: Engine Coolant Temperature (ECT) Sensor - (Except Diesel & Hybrid)) >> PINPOINT TEST DP: Output Shaft Speed (OSS) Sensor/Vehicle Speed Sensor (VSS)/Transfer Case Speed Sensor (TCSS) >> Test Procedure

Test Procedure

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  1. DP1 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTC) 
    NOTE: For vehicles with automatic transmission and (OSS) sensor DTCs, refer to the ENGINE CONTROLS - POWERTRAIN DTC CHARTS AND DESCRIPTIONS GASOLINE MODELS-->

    Are DTCs P0500, P0503, P0720, P0721, P0722, P0723, P1500, P1501, P1502 or P1900 present? 

    Yes No
    For DTCs P0500, P0503, P1500, P1501 or P1502, with manual shift transfer case,
    GO to  DP16.
    For DTCs P0500, P0720, P0721, P0722, P0723, P1502 or P1900, with a manual transmission or an electronic shift transfer case,
    GO to  DP2.
    For DTCs P0503 or P1500, with a manual transmission or an electronic shift transfer case,
    GO to  DP13.
    For DTC P1501, with a manual transmission or an electronic shift transfer case,
    GO to  DP12.    		 For all others, GO to DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS .
  2. DP2 DTCS P0500, P0720, P0721, P0722, P0723, P1502 AND P1900: VERIFY THE DRIVE CYCLE 
    • Access the PCM and monitor the OSS (RPM) PID.
    • Access the PCM and monitor the VSS (SPD) PID.
    • Drive the vehicle.
    • Monitor the PID in all transmission gear ranges while increasing and decreasing the speed.

    Does the PID reading increase and decrease with engine and vehicle speed? 

    Yes No
    GO to  DP3. GO to  DP4.
  3. DP3 VISUAL INSPECTION 
    • OSS/VSS connector disconnected.
    • Inspect the OSS/VSS harness for damage.
    • Inspect the OSS/VSS vehicle harness connector for damage and correct seating.
    • If possible, carry out a wiggle test.

    Is a concern present? 

    Yes No
    REPAIR as necessary.
    Clear the PCM DTCs. REPEAT the self-test.    		 GO to PINPOINT TEST Z .
  4. DP4 VERIFY THE TYPE OF OSS/VSS SENSOR 
    NOTE: The variable reluctance (VR) sensors have 2-wire connectors, Hall-effect sensors have 3-wire connectors.
    • Ignition OFF.
    • Inspect for a Hall-effect or a VR type of OSS/VSS sensor.

    Is this a Hall-effect type OSS/VSS sensor? 

    Yes No
    GO to  DP5. GO to  DP7.
  5. DP5 CHECK VOLTAGE TO THE OSS/VSS SENSOR 
    • Ignition OFF.
    • OSS/VSS connector disconnected.
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      VOLTAGE REFERENCE CHART

      (+) OSS/VSS Connector, Harness Side (-) Vehicle Battery
      VPWR Negative terminal

    Is the voltage greater than 10 V? 

    Yes No
    GO to  DP6. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test.
  6. DP6 CHECK THE VPWR GROUND TO THE OSS/VSS SENSOR 
    • Ignition OFF.
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) OSS/VSS Connector, Harness Side (-) Vehicle Battery
      PWRGND Negative terminal

    Is the resistance less than 5 ohms? 

    Yes No
    GO to  DP7. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test.
  7. DP7 CHECK THE OSS/VSS CIRCUIT FOR A SHORT TO VREF AND VOLTAGE IN THE HARNESS 
    • Ignition ON, engine OFF.
    • OSS/VSS connector disconnected.
    • Measure the voltage between:
      VOLTAGE REFERENCE CHART

      (+) OSS/VSS Connector, Harness Side (-) Vehicle Battery
      OSS/VSS Negative terminal

    Is the voltage less than 1 V? 

    Yes No
    GO to  DP8. REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test.
  8. DP8 CHECK THE OSS/VSS CIRCUIT(S) FOR AN OPEN IN THE HARNESS 
    NOTE: Hall-effect sensors are not equipped with a SIGRTN circuit. Disregard the SIGRTN measurement.
    • Ignition OFF.
    • PCM connector disconnected.
    • OSS/VSS connector disconnected.
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) PCM Connector, Harness Side (-) OSS/VSS Connector, Harness Side
      OSS/VSS OSS/VSS
      SIGRTN SIGRTN
      PWRGND PWRGND

    Are the resistances less than 5 ohms? 

    Yes No
    GO to  DP9. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test.
  9. DP9 CHECK THE OSS/VSS CIRCUIT FOR A SHORT TO GROUND IN THE HARNESS 
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) OSS/VSS Connector, Harness Side (-) OSS/VSS Connector, Harness Side
      OSS/VSS PWRGND

    Is the resistance greater than 10K ohms? 

    Yes No
    For Hall-effect sensors, GO to  DP10.
    For VR sensors, GO to  DP11.    		 REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test.
  10. DP10 CHECK THE OSS/VSS SIGNAL OUTPUT TO THE PCM, HALL-EFFECT TYPE SENSOR 
    NOTE: The opposite wheel must be held stationary.
    • PCM connector disconnected.
    • Raise the vehicle to allow for the rotation of the front drive wheels.
    • Ignition ON, engine OFF.
    • Transmission gear selector in NEUTRAL.
    • Measure the voltage between:
      VOLTAGE REFERENCE CHART

      (+) PCM Connector, Harness Side (-) PCM Connector, Harness Side
      OSS/VSS PWRGND
    • The voltage should rise above 5 volts and fall below 1 volt in a regular cycle. Observe several cycles.

    Does the OSS/VSS output voltage rise and fall as specified? 

    Yes No
    GO to  DP22. REMOVE the OSS/VSS sensor and INSPECT the target wheel. REPAIR as necessary. If OK, INSTALL a new OSS/VSS sensor. REFER to the appropriate Transfer Case article and appropriate Manual Transmission/Transaxle.
    Clear the PCM DTCs. REPEAT the self-test.
  11. DP11 CHECK THE RESISTANCE OF THE OSS/VSS SENSOR 
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) OSS/VSS Connector, Component Side (-) OSS/VSS Connector, Component Side
      OSS/VSS SIGRTN

    Is the resistance between 170 - 270 ohms (VSS) or 400 - 1.25K ohms (OSS)? 

    Yes No
    GO to  DP22. REMOVE the OSS/VSS sensor and INSPECT the target wheel. REPAIR as necessary. If OK, INSTALL a new OSS/VSS sensor. REFER to the appropriate Transfer Case and Manual Transmission/Transaxle article.
    Clear the PCM DTCs. REPEAT the self-test.
  12. DP12 KOER DTC P1501: CHECK THE VSS PID FOR AN INPUT SIGNAL 
    • Ignition ON, engine running.
    • Access the PCM and monitor the VSS (SPD) PID.
    • Observe the VSS input to the PCM.
    • Increase the engine speed, not greater than 2,000 RPM, several times while observing the VSS PID.

    Is the reading on the PID less than 5 km/h (3 mph)? 

    Yes No
    Unable to duplicate or identify the concern at this time. REFER to DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS for possible causes and additional DTC description information. If DTC P1501 still exists,
    GO to PINPOINT TEST Z .    		 GO to  DP15.
  13. DP13 DTCS P0503 AND P1500: INSPECT THE VSS AND THE CIRCUIT FOR AN INTERMITTENT 
    • Visually inspect the VSS and harness circuits for any potential failures.
    • Use the following check list for reference:
      • loose wires/connectors
      • pushed out connector pins
      • damaged wiring harness insulation
      • incorrect harness routing
      • incorrect VSS mounting

    Is a concern present? 

    Yes No
    REPAIR as necessary.
    Clear the PCM DTCs. REPEAT the self-test.    		 GO to  DP14.
  14. DP14 CHECK THE PCM VSS PID FOR AN INPUT SIGNAL 
    NOTE: For scan tools which have a data record feature, record the data for future playback to help identify any variations.
    • Access the PCM and monitor the VSS (SPD) PID.
    • Drive the vehicle at several steady state speeds above and below 50 km/h (30 mph).

    Are there any indicators of a noisy or intermittent signal with the VSS PID? 

    Yes No
    GO to  DP15. Unable to duplicate or identify the concern at this time. REPAIR any other DTCs.
    RETURN to SYMPTOM CHARTS for further direction.
  15. DP15 CHECK THE VSS HARNESS ROUTING 
    NOTE: Refer to Pinpoint Test Schematics and Connectors at the beginning of this pinpoint test.
    • Check the VSS harness routing:
      • Verify the harness is not routed adjacent to any high current wires such as ignition wires or generator wiring.
      • Verify the VSS harness is shielded and grounded, if applicable.
    • Measure the resistance of the VSS harness.

    Is a concern present? 

    Yes No
    REPAIR as necessary.
    Clear the PCM DTCs. REPEAT the self-test.    		 Unable to duplicate or identify the concern at this time. REFER to DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS for possible causes and additional DTC description information.
    GO to PINPOINT TEST Z .
  16. DP16 DTCS P0500, P0503, P1500, P1501 AND P1502: VISUAL INSPECTION OF THE TCSS 
    NOTE: The TCSS provides the rotational speed of the output shaft of the transfer case.

    The PCM uses this information to control the powertrain behavior and on some applications it is used as the source for the vehicle speed information.

    • TCSS connector disconnected.
    • Inspect the TCSS vehicle harness connector for damage and correct seating.

    Is a concern present? 

    Yes No
    REPAIR as necessary.
    Clear the PCM DTCs. REPEAT the self-test.    		 GO to  DP17.
  17. DP17 CHECK THE RESISTANCE OF THE TCSS 
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) TCSS Connector, Component Side (-) TCSS Connector, Component Side
      SIGRTN - Pin 1 TCSS - Pin 2

    Is the resistance between 1K - 1.25K ohms? 

    Yes No
    GO to  DP18. INSTALL a new TCSS. REFER to the appropriate Transfer Case article.
    Clear the PCM DTCs. REPEAT the self-test.
  18. DP18 CHECK THE TCSS SENSOR OUTPUT 
    NOTE: Hold the opposite wheel stationary.
    • With the vehicle in NEUTRAL and the parking brake off, position it on a hoist. Refer to the appropriate Jacking and Lifting article , for the locations of the lifting points.
    • Raise the vehicle.
    • Measure the frequency between:
      FREQUENCY REFERENCE CHART

      (+) TCSS Connector, Component Side (-) TCSS Connector, Component Side
      SIGRTN - Pin 1 TCSS - Pin 2
    • Monitor the TCSS signal while rotating the driven wheel as fast as possible.

    Does the frequency reading increase and decrease with the wheel speed? 

    Yes No
    GO to  DP19. REMOVE the TCSS and INSPECT the target wheel. REPAIR as necessary. If OK, INSTALL a new TCSS sensor. REFER to the appropriate Transfer Case article.
    Clear the PCM DTCs. REPEAT the self-test.
  19. DP19 CHECK THE TCSS CIRCUIT(S) FOR A SHORT TO GROUND AND VOLTAGE IN THE HARNESS 
    • Ignition ON, engine OFF.
    • TCSS connector disconnected.
    • Measure the voltage between:
      VOLTAGE REFERENCE CHART

      (+) TCSS Connector, Harness Side (-)
      TCSS - Pin 2 Ground

    Is the voltage less than 1 V? 

    Yes No
    GO to  DP20. REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test.
  20. DP20 CHECK THE CIRCUIT(S) FOR AN OPEN IN THE HARNESS 
    • Ignition OFF.
    • PCM connector disconnected.
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) PCM Connector, Harness Side (-) TCSS Connector, Harness Side
      TCSS TCSS - Pin 2
      SIGRTN SIGRTN - Pin 1

    Are the resistances less than 5 ohms? 

    Yes No
    GO to  DP21. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test.
  21. DP21 CHECK THE HARNESS FOR A SHORT TO GROUND 
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) TCSS Connector, Harness Side (-) TCSS Connector, Harness Side
      SIGRTN - Pin 1 TCSS - Pin 2
    • Measure the resistance between:
      RESISTANCE REFERENCE CHART

      (+) TCSS Connector, Harness Side (-)
      TCSS - Pin 2 Ground

    Are the resistances greater than 10K ohms? 

    Yes No
    GO to  DP22. REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test.
  22. DP22 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Visually inspect for:
      • pushed out pins
      • corrosion
    • Connect all the PCM connectors and make sure they seat correctly.
    • Carry out the PCM self-test.
    • Verify the concern is still present.

    Is the concern still present? 

    Yes No
    INSTALL a new PCM. REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) , PROGRAMMING THE VID BLOCK FOR A REPLACEMENT PCM . The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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