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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 QB: Glow Plug System (CALIFORNIA Emissions) >> Testing

Test QB: Glow Plug System (CALIFORNIA Emissions): Testing

WARNING: This page is about a different variant/trim than selected.
FAULT CODE SETTING CONDITION

Fault Code
(All except F650-750)		 KOEO KOER Continuous Memory
P0670 Test QB  , Step  6)   Test QB  , Step  6)
P0671   Test QB  , Step  1) Test QB  , Step  1)
P0672   Test QB  , Step  1) Test QB  , Step  1)
P0673   Test QB  , Step  1) Test QB  , Step  1)
P0674   Test QB  , Step  1) Test QB  , Step  1)
P0675   Test QB  , Step  1) Test QB  , Step  1)
P0676   Test QB  , Step  1) Test QB  , Step  1)
P0677   Test QB  , Step  1) Test QB  , Step  1)
P0678   Test QB  , Step  1) Test QB  , Step  1)
P0683   Test QB  , Step  11) Test QB  , Step  11)
CAUTION: When disconnecting Green and Black connectors at GPCM it is suggested that GPCM be unbolted from mounting bracket first and then connectors disconnected. This will allow for easier disconnect and will help prevent damage to connector terminals.
    NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  1. 1) Check For KOEO & Continuous Memory DTC P0671-P0678: Repeat KOER Self-Test
    These DTCs are set upon detection of a failed glow plug No. 1-8 respectively (P0671 = glow plug No. 1, P0672 = glow plug No. 2, etc.). DTC will also be set if an open, shorted to ground, or shorted to power condition occurs anywhere in the circuit. Possible causes are:
    • Open Or Shorted Glow Plug Circuit
    • Faulty Connector
    • Faulty GPCM
    • Faulty Glow Plug

    Perform KOER ON-DEMAND SELF-TEST  under QUICK TEST. Retrieve DTCs. If any glow plug DTCs (P0671-P0678) are present, go to next step. If no glow plug DTCs are present, go to step  6).

    2. NOTE: Glow plugs are numbered from front to rear with even numbered glow plugs on left side of engine.

  2. 2) Check For Faulty Glow Plug Circuit
    Turn ignition off. Disconnect GPCM connectors and inspect for damaged pins, corrosion and loose wires. GPCM is located on top of engine. See Figure or Figure . Repair connectors as necessary. Using DVOM, measure resistance between chassis ground and suspect glow plug terminal at GPCM harness connector. See GLOW PLUG DIAGNOSTIC TROUBLE CODE IDENTIFICATION  table to identify suspect glow plug. If resistance is more than 5 ohms, go to next step. If resistance is 5 ohms or less, replace suspect glow plug. Clear DTCs and retest. If DTC is still present, replace GPCM.
    GLOW PLUG DIAGNOSTIC TROUBLE CODE IDENTIFICATION

    DTC Glow Plug No.
    P0671 1
    P0672 2
    P0673 3
    P0674 4
    P0675 5
    P0676 6
    P0677 7
    P0678 8

  3. 3) Check Glow Plug Circuit For Open

    Disconnect 9-pin connector at valve cover gasket that corresponds to DTC. Inspect connector for damaged pins, corrosion and loose wires. Repair connector as necessary. Using DVOM, measure resistance of suspect circuit between appropriate terminal at valve cover gasket harness connector and appropriate terminal at GPCM harness connector. See Figure. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in affected circuit between valve cover gasket and GPCM. Clear DTCs and retest.

  4. 4) Check Glow Plug Circuit Under Valve Cover For Open

    Remove appropriate valve cover to access Under Valve Cover (UVC) wiring harness. Disconnect suspect glow plug connector. Using DVOM, measure resistance of circuit between terminal at disconnected glow plug harness connector and appropriate terminal at UVC harness connector. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, replace UVC wiring harness. Clear DTCs and retest.
    5. NOTE: Typical glow plug resistance is less than one ohm with a cold engine.

  5. 5) Check Glow Plug Resistance
    Using DVOM, measure resistance between chassis ground and suspect glow plug terminal. If resistance is more than 5 ohms, replace glow plug. Clear DTCs and retest. If resistance is 5 ohms or less, replace GPCM. Clear DTCs and retest.
    6. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  6. 6) Check For KOEO & Continuous Memory DTC P0670: Repeat KOEO Self-Test
    DTC P0670 is set when control circuit is open or shorted to ground or power. Possible causes are:
    • Open, Or Short To Ground Or Power In Control Circuit
    • Faulty GPCM Circuit
    • Faulty PCM Circuit

    Perform KOEO ON-DEMAND SELF-TEST  under QUICK TEST. Retrieve DTCs. If DTC P0670 is present, go to next step. If DTC P0670 is not present, go to step  11).

  7. 7) Check Control Line For Open

    Turn ignition off. Disconnect PCM connector. PCM is located in left rear of engine compartment, near brake master cylinder. Disconnect GPCM connectors. GPCM is located on top of engine. See Figure or Figure . Inspect connectors for damaged pins, corrosion and loose wires. Repair connectors as necessary. Install Rotunda Breakout Box (014-00950), leaving PCM disconnected. Using DVOM, measure resistance of Violet/Orange wire between test pin No. 101 at breakout box and terminal No. 8 at GPCM Green harness connector. See Figure. If resistance is 5 ohms or less, leave PCM and GPCM disconnected and go to next step. If resistance is more than 5 ohms, repair open in Violet/Orange wire between PCM and GPCM. Clear DTCs and retest.
    8. NOTE: Typical voltage on control circuit is less than one volt.

  8. 8) Check Control Line For Short To Power
    Turn ignition on. Using DVOM, measure voltage between chassis ground and test pin No. 101 at breakout box. If voltage is 5 volts or less, go to next step. If voltage is more than 5 volts, repair short to voltage in Violet/Orange wire between PCM and GPCM. Clear DTCs and retest.

  9. 9) Check Control Circuit For Short To Ground

    Turn ignition off. Using DVOM, measure resistance between chassis ground and test pin No. 101 at breakout box. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in Violet/Orange wire between PCM and GPCM. Clear DTCs and retest.

  10. 10) Check GPCM Function

    Ensure ignition is off. Reconnect PCM and GPCM connectors. Disconnect Engine Oil Temperature (EOT) sensor. This will maximize glow plug "on" time. EOT sensor is located on left side of engine. See Figure or Figure . Using DVOM, measure voltage between battery terminals. Turn ignition on. Note voltage reading within one minute of turning ignition on.
    NOTE: If voltage drops to less than 11 volts, recharge and test battery before continuing with this test.

    If battery voltage is okay, measure voltage between chassis ground and test pin No. 101 at breakout box with ignition on. Voltage should be less than one volt with glow plugs on. Wait at least 2 minutes for glow plug system to time out and note voltage reading. Voltage should be more than 10 volts with glow plugs off. If voltage readings are as specified, replace GPCM. Clear DTCs and retest. If voltage readings are not as specified, replace PCM. Clear DTCs and retest.

    11. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  11. 11) Check For KOER & Continuous Memory DTC P0683: Repeat KOER Self-Test
    DTC P0683 is set when PCM detects diagnostic line is open or shorted to ground or power. Possible causes are:
    • Open, Or Short To Ground Or Power In Diagnostic Line
    • Faulty GPCM Circuit
    • Faulty PCM Circuit

    Perform KOER ON-DEMAND SELF-TEST  under QUICK TEST. Retrieve Continuous Memory DTCs. If DTC P0670 is present with DTC P0683, repair DTC P0670 before continuing with this test. Go to step  6). If DTC P0683 is only DTC present, go to next step. If DTC P0683 is not present, no concern is indicated at this time. Test is complete.

  12. 12) Check Diagnostic Line For Open

    Turn ignition off. Disconnect PCM connector. PCM is located in left rear of engine compartment, near brake master cylinder. Disconnect GPCM connectors. GPCM is located on top of engine. See Figure or Figure . Inspect connectors for damaged pins, corrosion and loose wires. Repair connectors as necessary. Install Rotunda Breakout Box (014-00950), leaving PCM disconnected. Using DVOM, measure resistance of White/Light Green wire between test pin No. 8 at breakout box and terminal No. 9 at GPCM Green harness connector. See Figure. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in White/Light Green wire between PCM and GPCM. Clear DTCs and retest.
    13. NOTE: Typical voltage on diagnostic line is less than one volt.

  13. 13) Check Diagnostic Line For Short To Power
    Turn ignition on. Using DVOM, measure voltage between chassis ground and test pin No. 8 at breakout box. If voltage is 5 volt or less, go to next step. If voltage is more than 5 volt, repair short to voltage in White/Light Green wire between PCM and GPCM. Clear DTCs and retest.

  14. 14) Check Diagnostic Line For Short To Ground

    Turn ignition off. Reconnect PCM and GPCM connectors. Turn ignition on. Using DVOM, measure voltage between chassis ground and test pin No. 8 at breakout box. If circuit is not shorted, voltage should pulse from zero volt to 12 volts. If voltage is zero volt, repair short to ground in White/Light Green wire between PCM and GPCM. Clear DTCs and retest. If voltage pulses, go to next step.

  15. 15) Check GPCM Diagnostic Line

    Turn ignition off. Ensure GPCM connector is connected, and PCM is connected to breakout box. Using scan tool, perform the following:
    • Select VEHICLE and ENGINE.
    • Select DIGITAL MEASUREMENT SYSTEM.
    • Select FREQUENCY METER.
    • Change level to 6 VOLT DC.
    • Connect scan tool SIG INPUT probe to PCM breakout box terminal No. 8 (GPCM diagnostic line).
    NOTE: Typical frequency for diagnostic signal with all plugs functioning is maximum 7 Hz. Typical frequency for signal with one or more glow plugs failed is maximum 15 Hz.

    Disconnect Engine Oil Temperature (EOT) sensor. This will maximize glow plug "on" time. EOT sensor is located on left side of engine. See Figure or Figure . Using scan tool, access frequency meter. Turn ignition on. Wait about 5 seconds for frequency to stabilize. If frequency reading is 5-10 Hz, replace PCM. Clear DTCs and retest. If frequency reading is not 5-10 Hz, replace GPCM. Clear DTCs and retest.

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