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Possible Causes

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No communication with ECS module could be caused by damaged wiring on ignition circuit No. 298 (Violet/Orange wire), damaged wiring on circuit No. 70 (Light Blue/White wire), poor ECS module ground, damaged scan tool or low battery voltage condition.

  1. Check scan tool setup

    Turn ignition switch off. Connect scan tool to Data Link Connector (DLC). See USING SCAN TOOL  under DIAGNOSTICS. Turn ignition switch to RUN position. Verify that scan tool is firmly connected to DLC. If diagnostics other than ECS module can be accessed through DLC, go to next step. If diagnostics other than ECS module can not be accessed through DLC, verify that scan tool is functioning properly. If not, repair or replace scan tool.

  2. Check ignition voltage

    Turn ignition switch to OFF position. Disable air bag system. See DISABLING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM. Access and disconnect ECS module harness connector. See ELECTRONIC CRASH SENSOR (ECS) MODULE  under REMOVAL & INSTALLATION. Turn ignition switch to RUN position. Measure voltage between ground and harness side of ECS module connector terminal No. 2 (Violet/Orange wire). Measure voltage between ground and harness side of ECS module connector terminal No. 17 (Red/White wire, circuit No. 937). If voltage is equal to battery voltage in both circuits, go to next step. If voltage is not equal to battery voltage in either circuit, repair open in appropriate wire. See WIRING DIAGRAMS . Go to step  5.

  3. Check ECS module ground

    Measure resistance between ground and harness side of ECS module connector terminals No. 18 and 21 (Black/Light Blue wire, circuit No. 875). If resistance is less than 3 ohms, go to next step. If resistance is more than 3 ohms, repair open in appropriate Black/Light Blue wire. Go to step  5.

  4. Check DLC circuit No. 70 for open

    Measure resistance of Light Blue/White wire between harness side of ECS module connector terminal No. 19 and DLC terminal No. 7. See Figure & Fig 1 . If resistance is less than 3 ohms, check for causes of intermittent high resistance on circuits. Attempt to recreate hard fault by flexing wire harness and cycling ignition key. Repair any intermittent problems found. If no intermittent problems are found, replace ECS module. Go to next step. If resistance is not less than 3 ohms, repair open in Light Blue/White wire. Go to next step.

  5. Check for communication

    Reconnect ECS module harness connector. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to RUN position. Retrieve Continuous DTCs. If continuous DTCs are retrieved, go to diagnostic trouble code identification table for direction to appropriate test. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION  table. DO NOT clear DTCs until all DTCs have been resolved. If no continuous DTCs were retrieved, reconnect air bag system. Activate air bag system. See ACTIVATING SYSTEM  under DISABLING & ACTIVATING AIR BAG SYSTEM.
    Fig 1: Identifying Data Link Connector (DLC)
    G98H08170Courtesy of FORD MOTOR CO.
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