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Home >> Ford >> 2000 >> Excursion 7.3 F, RWD >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Supplemental Inflatable Restraint System - Excursion & Super Duty >> Diagnostic Tests >> Test O: Passenger Air Bag Deactivation (Pad) Switch Fault (DTC B1871) >> Possible Causes

Possible Causes

An invalid PAD switch resistance could be caused by damaged or inoperative PAD switch, damaged or inoperative ECS, a short to battery, short to ground or open in circuit 1112 (White/Light Blue wire).

  1. Check for hard or intermittent DTC

    Ensure ignition is off. Connect scan tool to DLC. See USING SCAN TOOL  under DIAGNOSTICS. 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 B1871 was retrieved during on-demand self-test, fault is hard. Go to next step. If DTC B1871 was not retrieved, fault is intermittent. Go to step  6.

  2. Check PAD switch on position

    Turn ignition off. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access ECS and disconnect harness connector. See ELECTRONIC CRASH SENSOR  under REMOVAL & INSTALLATION. Turn PAD switch to ON position. Measure resistance between ECS connector terminals No. 9 (White/Light Blue wire) and No. 21 (Black/Orange wire). See Figure. If resistance is 900-1100 ohms, go to next step. If resistance is not 900-1100 ohms, go to step  4.

  3. Check PAD switch off position

    Turn PAD switch to OFF position. Measure resistance between ECS connector terminals No. 9 (White/Light Blue wire) and No. 21 (Black/Orange wire). If resistance is 400-600 ohms, replace ECS. Go to step  7. If resistance is not 400-600 ohms, go to next step.

  4. Check circuit for short to battery

    Disconnect negative battery cable. Turn ignition switch to RUN position. Measure resistance between ECS connector terminal No. 9 (White/Light Blue wire) and terminals No. 21 (Black/Orange wire) and No. 17 (Red/White wire) independently. If resistance is less than 100 ohms, repair short to battery in White/Light Blue wire. Go to step  7. If resistance is more than 100 ohms, go to next step.

  5. Check circuit for open

    Turn ignition off. Access PAD switch and disconnect connector. See PASSENGER-SIDE AIR BAG DEACTIVATE (PAD) SWITCH  under REMOVAL & INSTALLATION. Measure resistance of White/Light Blue wire between ECS connector terminal No. 9 and PAD switch harness connector. If resistance is less than 10 ohms, replace PAD switch. Go to step  7. If resistance is more than 10 ohms, repair open in White/Light Blue wire. Go to step  7.

  6. Check for intermittent fault

    Refer to continuous DTCs recorded in step  1. If DTC retrieved in step  1 was an intermittent fault, check for cause of intermittent faults on circuit 1112 (White/Light Blue wire). 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 an intermittent fault, go to next step.

  7. 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 (DTC) IDENTIFICATION  table. If no continuous DTCs were retrieved, reconnect air bag system. Activate 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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