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Home >> Ford >> 2000 >> Taurus LX, 3.0 2, AX4N >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Supplemental Inflatable Restraint System >> Diagnostic Tests >> Test M: Seat Position Switch Fault (DTC C1946) >> Possible Causes

Possible Causes

A seat position switch fault could be caused by an RCM internal fault, short to battery on circuit 1520 (Light Green wire), high or low resistance on circuits 1520 (Light Green wire) or 442 (Light Green/Orange wire), or a worn or damaged seat position sensor.

  1. Check for hard or intermittent DTC

    Ensure ignition is off. Connect scan tool to DLC. See USING SCAN TOOL  . Turn ignition switch to RUN position. Retrieve and record any continuous DTCs. See RETRIEVING FAULT CODES  under DIAGNOSTICS. Perform on-demand self-test. See ON-DEMAND SELF-TEST  under DIAGNOSTICS. If DTC C1946 was retrieved during on-demand self-test, fault is hard. Go to next step. If DTC C1946 was not retrieved, fault is intermittent. Go to step  7 .
    NOTE: While measuring resistance in following test, operate various electrical systems such as radio, windows and blower motor.

  2. Check harness for short to battery or ground

    Turn ignition off. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access RCM and disconnect both harness connectors. See RESTRAINTS CONTROL MODULE  under REMOVAL & INSTALLATION. Leave negative battery cable disconnected. Turn ignition switch to RUN position. Measure resistance between RCM harness connectors C310A, terminal No. 1 (White/Yellow wire) and 310B, terminals No. 8 (Light Green wire) and No. 9 (Light Green/Orange wire). See Figure . Measure resistance between RCM harness connectors C310A, terminal No. 10 (Black/Orange wire) and 310B, terminals No. 8 (Light Green wire) and No. 9 (Light Green/Orange wire). If resistance is less than 10 k/ohms at any terminal, repair short to battery or ground on appropriate wire. Go to step  8 . If resistance is more than 10 k/ohms, go to next step.

  3. Check harness for continuity

    Measure resistance of Light Green wire between RCM harness connector 310B, terminal No. 8 and driver"s seat floor connector C313, terminal No. 7. See Figure . Measure resistance of Light Green/Orange wire between RCM harness connector 310B, terminal No. 9 and driver"s seat floor connector C313, terminal No. 2. If either resistance is more than 10 ohms, repair high resistance in vehicle harness. See WIRING DIAGRAMS  . Go to step  8 . If all resistance is less than 10 ohm, go to next step.

  4. Check in-seat harness for short

    Access and disconnect driver-side seat belt pretensioner connector. See SEAT BELT PRETENSIONER  under REMOVAL & INSTALLATION. Disconnect 3-pin seat position sensor connector. Measure resistance between in-seat harness connector C313, terminal No. 7 (Light Green wire) and all other terminals of connector. See Figure . Measure resistance between in-seat harness connector C313, terminal No. 2 (Light Green/Orange wire) and all other terminals of connector. If any resistance is less than 10 k/ohms, replace in-seat harness. Go to step  8 . If resistance is more than 10 k/ohms, go to next step.

  5. Check in-seat harness for continuity

    Measure resistance of Light Green wire between in-seat harness connector C313, terminal No. 7 and 3-pin seat position sensor connector. Measure resistance of Light Green/Orange wire between in-seat harness connector C313, terminal No. 2 and 3-pin seat position sensor connector. If either resistance is more than 10 ohms, replace in-seat harness. Go to step  8 . If resistance is less than 10 ohms, install a known-good seat position sensor. Go to next step.

  6. Check for DTCs

    Reconnect seat position sensor connector. Reconnect driver-side seat belt pretensioner connector. Reactivate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Perform on-demand self-test. See ON-DEMAND SELF-TEST  under DIAGNOSTICS. If DTC C1946 was retrieved during on-demand self-test, replace RCM. Reinstall original seat position sensor and go to step  8 . If DTC C1946 was not retrieved during on-demand self-test, system is functioning properly. Go to step  8 .

  7. Check for intermittent fault

    Refer to continuous DTCs recorded in step  1 . If DTC retrieved in step  1 was a intermittent fault, check for cause of intermittent condition on Light Green wire (circuit 1520) or Light Green/Orange wire (circuit 442). Attempt to recreate fault by flexing wire harness and cycling ignition switch frequently. Repair any intermittent problems found. Go to next step. If DTC retrieved in step  1 was not a intermittent fault, go to next step.

  8. Check for additional DTCs

    Refer to continuous DTCs recorded in step  1 . If any continuous DTCs were retrieved, go to diagnostic trouble code identification table for direction to appropriate test. See DIAGNOSTIC TROUBLE CODE IDENTIFICATION  table. If no DTCs were retrieved, reconnect air bag system. Reactivate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Prove out system. Clear all DTCs. See CLEARING FAULT CODES  under DIAGNOSTICS.
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