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Home >> Ford >> 2003 >> Excursion 6.0 P, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 7.3L (995, 996 F650/750, 99F E Series & 99F F450/550) DIESEL) >> System Tests >> Test NB: Check Engine Light >> Testing

Test NB: Check Engine Light: Testing

WARNING: This page is about a different variant/trim than selected.
    NOTE: For Econoline and F650-750 models, go directly to step  3).

  1. 1) CHECK ENGINE Light Fault
    Turn ignition on. If any KOEO or Continuous Memory DTCs exist, service them before proceeding. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If CHECK ENGINE light is always illuminated, go to appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT to diagnose CHECK ENGINE light always on. If CHECK ENGINE light is not always on, go to next step.

  2. 2) Check ENGINE Light Never On

    Disconnect MAP sensor to force CHECK ENGINE light to illuminate. Cycle key on and off 2 times waiting at least 10 seconds between cycles. If CHECK ENGINE light illuminates, system is functioning correctly. Retest system. If CHECK ENGINE light does not illuminate, go to TEST N under SYSTEM TESTS in ANALOG INSTRUMENT PANELS - EXCURSION & F250-550 article in ACCESSORIES & EQUIPMENT to diagnose instrument cluster. Retest system.

  3. 3) CHECK ENGINE Light Fault

    Turn ignition on. If any KOEO or Continuous Memory DTCs exist, service them before proceeding. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If CHECK ENGINE light is always illuminated, go to next step. If CHECK ENGINE light is not always on, go to step  5).

  4. 4) CHECK ENGINE Light Always On: Check Circuit No. 658 (Pink/Light Green Wire) For Short To Ground

    Turn ignition off. Disconnect PCM connector and inspect for damaged pins, corrosion and loose wires. PCM is located in left rear of engine compartment, near brake master cylinder. Repair connector as necessary. Turn ignition on. If CHECK ENGINE light is illuminated, repair short to ground in circuit No. 658 (Pink/Light Green wire) between PCM and instrument cluster. See Figure or Figure . Clear DTCs and retest. If CHECK ENGINE light is off, replace PCM. Clear DTCs and retest.

  5. 5) CHECK ENGINE Light Never On

    Turn ignition off. Disconnect MAP sensor connector and inspect for damaged pins, corrosion and loose wires. MAP sensor is located in rear of engine compartment, mounted on cowl. Repair connector as necessary. Start engine and allow to idle. If CHECK ENGINE light is illuminated, system is operating correctly. Clear DTCs and retest. If CHECK ENGINE light is not illuminated, reconnect MAP sensor and go to next step.

  6. 6) Check Ignition Feed Circuit

    Turn ignition on. Using DVOM, measure voltage between chassis ground and input side of fuse No. 2 (Econoline) or fuse No. 29 (F650-750) at central junction box. Central junction box is located behind lower left side of instrument panel. If battery voltage is present, go to next step. If battery voltage is not present, locate and repair open in power circuit (Red/Light Green wire on Econoline or Dark Blue/Light Green wire on F650-750) between ignition switch and appropriate fuse in central junction box. If power circuit is okay, replace defective ignition switch. Clear DTCs and retest.

  7. 7) Check Fuse

    Remove and inspect CHECK ENGINE light PWR fuse No. 2 (Econoline) or fuse No. 29 (F650-750) from central junction box. If fuse is okay, go to next step. If fuse is blown, locate and repair short to ground in Red/Yellow wire between central junction box and instrument cluster. Replace fuse. Clear DTCs and retest.

  8. 8) Check PWR Feed Circuit To CHECK ENGINE Light For Open

    Ensure CHECK ENGINE light PWR fuse No. 2 (Econoline) or fuse No. 29 (F650-750) is removed. Remove CHECK ENGINE light bulb. Using DVOM, measure resistance of Red/Yellow wire between output side of CHECK ENGINE light PWR fuse at central junction box and power side of CHECK ENGINE light bulb socket. If resistance is less than 5 ohms, PWR feed circuit to CHECK ENGINE light is okay. Go to next step. If resistance is 5 ohms or more, locate and repair open in Red/Yellow wire. Clear DTCs and retest.

  9. 9) Inspect CHECK ENGINE Light Bulb

    Inspect CHECK ENGINE light bulb. If bulb is okay, go to next step. If bulb is bad, replace bulb. Clear DTCs and retest.

  10. 10) Check Signal Circuit To CHECK ENGINE Light For Open

    Disconnect PCM connector and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install Rotunda Breakout Box (014-00950), leaving PCM disconnected. Using DVOM, measure resistance of CHECK ENGINE light signal circuit (Pink/Light Green wire) between CHECK ENGINE light bulb socket and test pin No. 2 at breakout box. If resistance is less than 5 ohms, signal circuit is okay. Replace PCM. Clear DTCs and retest. If resistance is 5 ohms or more, locate and repair open in signal circuit (Pink/Light Green wire). Reconnect all components, clear DTCs and retest.
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