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Home >> Mercury >> 2004 >> Monterey >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Pinpoint Test DK: Accelerator Pedal Position Sensor Through Pinpoint Test DV: Throttle Body Assembly Etc - CNG, Flex-Fuel & Gasoline >> Pinpoint Test DP: Vehicle Speed Sensor (VSS)/Transfer Case Speed Sensor (TCSS) >> Test Procedure
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Test Procedure

  1. DP1 DTCS P0500, P0501 AND P1502: CHECK THE VSS CIRCUIT(S) FOR AN OPEN IN THE HARNESS 
    NOTE: REFER to the POWERTRAIN CONTROL MODULE (PCM) CONNECTOR  in the beginning of this pinpoint test.
    • PCM connector disconnected.
    • VSS connector disconnected.
    • Measure the resistance between:
    ( + )PCM Connector, Harness Side ( - )VSS Connector, Harness Side
    VSS VSS - Pin 2
    VSS-GND VSS-GND - Pin 1

    Are the resistances less than 5 ohms? 

    Yes No
    GO to  DP2. REPAIR open circuit.
    CARRY OUT an OBD drive cycle. Refer to DRIVE CYCLES .
  2. DP2 CHECK THE VSS CIRCUIT(S) FOR A SHORT TO GROUND AND POWER IN THE HARNESS 
    • Measure the resistance between:
    ( + )VSS Connector, Harness Side ( - )VSS Connector, Harness Side
    VSS-GND - Pin 1 VSS - Pin 2
    • Measure the resistance between:
    ( + )PCM Connector, Harness Side ( - )VSS Connector, Harness Side
    SIGRTN VSS - Pin 2
    VPWR VSS - Pin 2

    Are the resistances greater than 5 ohms? 

    Yes No
    GO to  DP3. GO to  DP4.
  3. DP3 CHECK THE VSS RESISTANCE 
    • Measure the resistance between:
    ( + )VSS Connector, Component Side ( - )VSS Connector, Component Side
    VSS-GND - Pin 1 VSS - Pin 2

    Is the resistance between 170 ohms - 270 ohms? 

    Yes No
    REPLACE the PCM. REFER to FLASH ELECTRICALLY ERASEABLE PROGRAMMABLE READ ONLY MEMORY - FLASH EEPROM .
    CARRY OUT an OBD drive cycle. Refer to DRIVE CYCLES .    		 REPLACE the VSS sensor.
    CARRY OUT an OBD drive cycle. Refer to DRIVE CYCLES .
  4. DP4 VERIFY IF THE VSS CIRCUIT IS SHORTED IN HARNESS OR OTHER MODULE(S) 
    • Determine which, if any, modules are connected to the VSS circuit. Refer to the appropriate SYSTEM WIRING DIAGRAMS article.
    • If no other modules are connected to the VSS circuit, Go to the YES Action to Take.
    • One at a time, disconnect the modules associated with the VSS circuit.
    • After disconnecting each module, TEST again for a short circuit. Refer to test step that sent you here). Repeat until each associated module is disconnected or the short circuit is eliminated.

    Does the short circuit remain after all associated modules are disconnected? 

    Yes No
    REPAIR short circuit.
    CARRY OUT an OBD drive cycle. Refer to DRIVE CYCLES .    		 REFER to the appropriate service information article for further diagnosis of the appropriate module.
  5. DP5 KOER DTC P1501: CHECK THE VSS PID FOR AN INPUT SIGNAL 
    • Key ON Engine RUN.
    • Access the PCM -VSS 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 fault at this time.
    REFER to POWERTRAIN DTC CHARTS & DESCRIPTIONS - CNG, FLEX-FUEL & GASOLINE , DTCs description for a list of possible causes.
    If DTC P1501 still exists
    GO to PINPOINT TEST Z step 1 .    		 GO to  DP8.
  6. DP6 DTC P0503: INSPECT THE VSS AND 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.

    Did the visual inspection reveal a potential failure? 

    Yes No
    Repair the fault as necessary. CARRY OUT an OBD drive cycle.
    Refer to DRIVE CYCLES .    		 GO to  DP7.
  7. DP7 CHECK THE PCM VSS PID FOR AN INPUT SIGNAL 
    • Access the PCM -VSS PID.
    • Drive the vehicle at several steady state speeds above and below 50 km/h (30 mph).
    • NOTE: For scan tools which have a data record feature, record data for playback to help identify variations.
    • During each steady state speed observe the VSS PID for variations of (+) or (-) 8 km/h (5 mph) for greater than 10 seconds.

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

    Yes No
    GO to  DP8. Unable to duplicate or identify the fault at this time.
    REPAIR any other DTCs.
  8. DP8 CHECK THE VSS HARNESS ROUTING 
    • CHECK the VSS harness routing.
    • Verify the harness is not routed adjacent to 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.
    • REFER to Pinpoint Test Schematic and Connectors in the INTRODUCTION  at beginning of this pinpoint test.

    Are any concerns evident? 

    Yes No
    REPAIR as necessary.
    CARRY OUT an OBD drive cycle. Refer to DRIVE CYCLES .    		 Unable to duplicate or identify the fault at this time.
    REFER to POWERTRAIN DTC CHARTS & DESCRIPTIONS - CNG, FLEX-FUEL & GASOLINE , DTCs description for a list of possible causes.
    GO to PINPOINT TEST Z step 1 .
  9. DP9 DTCS P0500 AND P1502: VISUAL INSPECTION OF TCSS 
    • NOTE: The transfer case speed sensor TCSS provides the rotational speed of the output shaft of the transfer case.
    • The PCM uses this information to control powertrain behavior and on some applications is used as the source of vehicle speed information.
    • TCSS connector disconnected.
    • INSPECT the TCSS vehicle harness connector for damage and proper seating.

    Have any problems been found? 

    Yes No
    REPAIR as necessary. GO to  DP10.
  10. DP10 CHECK THE RESISTANCE OF THE TCSS SENSOR 
    • Measure the resistance between:
    ( + )TCSS Connector, Component Side ( - )TCSS Connector, Component Side
    SIGRTN - Pin 1 TCSS - Pin 2

    Is the resistance between 1K ohms - 1.25K ohms? 

    Yes No
    GO to  DP11. REPLACE the TCSS sensor.
  11. DP11 CHECK THE TCSS SENSOR OUTPUT 
    • Raise the vehicle on a wheel free two post lift. Put the vehicle in neutral with the Parking Brake off. Take safety precautions as necessary.
    • Measure the Frequency between:
    ( + )TCSS Connector, Component Side ( - )TCSS Connector, Component Side
    SIGRTN - Pin 1 TCSS - Pin 2

    Does the frequency reading increase and decrease with wheel speed? 

    Yes No
    GO to  DP12. REMOVE the TCSS and inspect the target wheel.
    REPAIR as necessary.
    If OK, REPLACE the TCSS sensor.
  12. DP12 CHECK THE TCSS CIRCUIT FOR A SHORT TO POWER IN THE HARNESS 
    • Key ON Engine OFF.
    • TCSS connector disconnected.
    • Measure the voltage between:
    ( + )TCSS Connector, Harness Side ( - )
    TCSS - Pin 2 Ground

    Is the voltage less than 1 V? 

    Yes No
    KEY OFF.
    GO to  DP13.    		 KEY OFF.
    REPAIR the short circuit.
  13. DP13 CHECK THE CIRCUIT(S) FOR AN OPEN IN THE HARNESS 
    • PCM connector disconnected.
    • Measure the resistance between:
    ( + )PCM Connector, Harness Side ( - )TCSS Connector, Harness Side
    TCSS
    SIGRTN    		 TCSS - Pin 2
    SIGRTN - Pin 1

    Are the resistances less than 5 ohms? 

    Yes No
    GO to  DP14. REPAIR the open circuit.
  14. DP14 CHECK THE TCSS CIRCUIT(S) FOR A SHORT TO GROUND AND POWER IN THE HARNESS 
    • Measure the resistance between:
    ( + )TCSS Connector, Harness Side ( - )TCSS Connector, Harness Side
    SIGRTN - Pin 1 TCSS - Pin 2
    • Measure the resistance between:
    ( + )TCSS Connector, Harness Side ( - )
    TCSS - Pin 2 Ground

    Are all the resistances greater than 10K ohms? 

    Yes No
    REPLACE the PCM. REFER to FLASH ELECTRICALLY ERASEABLE PROGRAMMABLE READ ONLY MEMORY - FLASH EEPROM . REPAIR the short circuit.
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