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2003 Grand Marquis digital speedo only reads "0". All other displays read correctly. Could it be the speed control? If so, where exactly is it located?

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The speedometer provides speed information based on a speed/distance pulse signal from the vehicle speed sensor (VSS). The VSS is mounted on the speedometer driven gear in the transmission.
or the gauge is bad .

  • The speedometer/odometer is inoperative
  • CJB fuse 14 (10A).
  • Vehicle speed sensor (VSS).
  • Circuitry.
  • Instrument cluster.
  • Go To Pinpoint Test E .
PINPOINT TEST E: THE SPEEDOMETER/ODOMETER IS INOPERATIVE CAUTION: Use the correct probe adaptor(s) when making measurements. Failure to use the correct probe adaptor(s) may damage the connector.
VSS C1088
Raise the drive wheels off the ground. While rotating the driveshaft, measure the AC voltage between the VSS C1088 pin 1, circuit 679 (GY/BK), component side and the VSS C1088 pin 2, circuit 676 (PK/OG), component side.
  • Is the voltage between 1.3 volts AC to 6.1 volts AC?
Yes GO to E2 .

No CHECK and INSPECT the speedometer drive gear. INSTALL a new VSS if the speedometer drive gear is OK. TEST the system for normal operation E2 CHECK CIRCUIT 679 (GY/BK) AND CIRCUIT 676 (PK/OG) BETWEEN THE INSTRUMENT CLUSTER AND THE VSS

Posted on Dec 03, 2016

  • Jeff Armer Dec 03, 2016

    Instrument Cluster C220b

    Measure the resistance between the instrument cluster C220b pin 12, circuit 679 (GY/BK), harness side and the VSS C1088 pin 1, circuit 679 (GY/BK), harness side; and between the instrument cluster C220b pin 12, circuit 679 (GY/BK), harness side and ground.

    Measure the resistance between the instrument cluster C220b pin 8, circuit 676 (PK/OG), harness side and the VSS C1088 pin 2, circuit 676 (PK/OG), harness side; and between the instrument cluster C220b pin 8, circuit 676 (PK/OG), harness side and ground.

    Are the resistances less than 5 ohms between the instrument cluster and the VSS; and greater than 10,000 ohms between the instrument cluster and ground?
    GO to E3 .

    REPAIR the circuit. TEST the system for normal operation.
    Disconnect all instrument cluster connectors.
    Check for:
    pushed-out pins

    Connect all instrument cluster connectors and make sure they seat correctly.
    Operate the system and verify the concern is still present.

    Is the concern still present?
    INSTALL a new instrument cluster. REFER to Instrument Cluster in this section. REPEAT the instrument cluster self-test.

    The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.



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