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Diagnostic Aids

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    NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket.

  1. 1) DTC 0261, 0264, 0267, 0270, 0273, 0276, 0279 Or 0282: Check For Short To Ground In Low Side Circuit
    These DTCs indicate a short to ground on low side circuit between Injector Driver Module (IDM) and injector. Identify DTC and refer to INJECTOR DTC 0261-0282 CIRCUIT IDENTIFICATION  table to determine which circuit to check.
    INJECTOR DTC 0261-0282 CIRCUIT IDENTIFICATION

    Cylinder No. DTC Low Circuit No. (Wire Color)
    1 0261 555 (Tan)
    2 0264 556 (White)
    3 0267 557 (Brown/Yellow)
    4 0270 558 (Brown/Light Blue)
    5 0273 559 (Tan/Black)
    6 0276 560 (Light Green/Orange)
    7 0279 561 (Tan/Red)
    8 0282 562 (Light Blue)

    Turn ignition off. Disconnect suspect injector connector at valve cover gasket. Measure resistance between ground and suspect circuit terminal at engine wiring harness 42-pin connector. See Figure. Connector is located on top of left side wheelwell. See INJECTOR DTC 0261-0282 CIRCUIT IDENTIFICATION  table. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, go to step  4).

  2. 2) Check For Short To Ground

    Install Glow Plug Injector Adapter (014-00935) to injector connector at valve cover gasket. Measure resistance between ground and suspect circuit at glow plug injector adapter. If resistance is more than 10 k/ohms, fault may be intermittent. Go to step  5). If resistance is 10 k/ohms or less, go to next step.

  3. 3) Inspect Wiring Harness For Short

    Remove valve cover. Disconnect suspect injector connector. Inspect Under Valve Cover (UVC) wiring harness for short to ground. Replace wiring harness as necessary. Clear DTCs, and repeat QUICK TEST . If wiring harness is okay, replace injector. Clear DTCs, and repeat QUICK TEST .

  4. 4) Check For Short

    Disconnect IDM 40-pin connector. IDM is located in left side of engine compartment. Measure resistance at IDM wiring harness connector between suspect injector circuit terminal, and all other circuits of IDM connector and to ground. If all readings are more than 10 k/ohms, replace IDM. Clear DTCs, and repeat QUICK TEST . If any reading is 10 k/ohms or less, locate and repair short between injector connector at valve cover and IDM connector. Clear DTCs, and repeat QUICK TEST .

  5. 5) Check For Intermittent Short To Ground

    Turn ignition off. Disconnect IDM 40-pin connector. IDM is located in left side of engine. Reconnect all other connectors. Connect DVOM between ground and suspect injector circuit terminal at IDM wiring harness connector. While observing DVOM, wiggle and bend small sections of wiring harness starting at suspect injector connector and working toward IDM. If resistance changes to less than 10 k/ohms at any time, isolate fault and repair as necessary. Clear DTCs, and repeat QUICK TEST . If resistance does not change to less than 10 k/ohms, replace IDM. Clear DTCs, and repeat QUICK TEST .
    6. NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket.

  6. 6) DTC 0262, 0265, 0268, 0271, 0274, 0277, 0280, 0283 Or 1261-1268: Check For Short To B+ Or To High Side In Low Side Circuit
    These DTCs indicate that low side circuit is shorted to power or high side circuit is shorted between IDM and fuel injector. Identify DTC and refer to INJECTOR DTC & CIRCUIT IDENTIFICATION  table to determine which circuit to check. Turn ignition on. Disconnect IDM 40-pin connector. IDM is located in left side of engine compartment. Disconnect suspect injector connector at valve cover gasket. Also, disconnect remaining injector connector on same cylinder bank. Measure resistance between positive battery terminal and low side circuit terminal at suspect injector connector at valve cover gasket. Also, measure resistance between positive battery terminal and high side circuit terminal at suspect injector connector at valve cover gasket connector. If both readings are less than 10 k/ohms, go to next step. If any reading is 10 k/ohms or more, locate and repair short to power in suspect circuit between IDM and injector connector at valve cover gasket.
    INJECTOR DTC & CIRCUIT IDENTIFICATION

    Cylinder No. DTC Low Side Circuit (Wire Color) High Side Circuit (Wire Color)
    1 1261-0262 555 (Tan) 1087 (Orange)
    2 1262-0265 556 (White) 878 (Pink/Yellow)
    3 1263-0268 557 (Brown/Yellow) 1087 (Orange)
    4 1264-0271 558 (Brown/Light Blue) 878 (Pink/Yellow)
    5 1265-0274 559 (Tan/Black) 1087 (Orange)
    6 1266-0277 560 (Light Green/Orange) 878 (Pink/Yellow)
    7 1267-0280 561 (Tan/Red) 1087 (Orange)
    8 1268-0283 562 (Light Blue) 878 (Pink/Yellow)

  7. 7) Check For Short To Valve Cover

    Install Glow Plug Injector Adapter (014-00935) to injector connector at valve cover gasket. Measure resistance between high side and low side circuit terminals at glow plug injector adapter. If resistance is less than 2 ohms (engine cold), go to next step. If resistance 2 ohms or more, fault may be intermittent. Go to step  10).

  8. 8) Check For Short Under Valve Cover

    Remove valve cover. Disconnect suspect injector connector. Measure resistance of both high and low side circuits between glow plug injector adapter and suspect injector connector. If both readings are more than 10 k/ohms, replace injector. Clear DTCs, and repeat QUICK TEST . If any reading is 10 k/ohms or less, go to next step.

  9. 9) Check Gasket Harness Or UVC Short Low Side To High Side

    Remove Under Valve Cover (UVC) wiring harness. Measure resistance between low side and high side circuits at valve cover gasket wiring harness. If resistance is less than 5 ohms, replace gasket wiring harness. Clear DTCs, and repeat QUICK TEST . If resistance is 5 ohms or more, replace UVC wiring harness. Clear DTCs, and repeat QUICK TEST .

  10. 10) Check For Intermittent Low Side Short To Power Or High Side

    Turn ignition off. Disconnect IDM 40-pin connector. IDM is located in left side of engine. Disconnect all 4 injector connectors at valve cover gaskets. Connect DVOM between positive battery terminal and suspect injector low side circuit terminal at IDM wiring harness connector. While observing DVOM, wiggle and bend small sections of wiring harness starting at suspect injector connector and working toward IDM. Repeat wiggle test for suspect injector high side circuit. If resistance changes to less than 10 k/ohms at any time, isolate fault and repair as necessary. Clear DTCs, and repeat QUICK TEST . If resistance does not change to less than 10 k/ohms, replace IDM. Clear DTCs, and repeat QUICK TEST .
    11. NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket.

  11. 11) DTC 1271-1278: Check For Open Between Injector High Side To Low Side At Valve Cover Connector
    These DTCs indicate an open in low side circuit or high side circuit between IDM and fuel injector. Identify DTC and refer to INJECTOR DTC 1271-1278 CIRCUIT IDENTIFICATION  table to determine which circuit to check. Turn ignition off. Disconnect suspect injector connector at valve cover gasket. Install Glow Plug Injector Adapter (014-00935) to injector connector at valve cover gasket. Measure resistance between high side and low side circuit terminals at glow plug injector adapter. If resistance is less than 5 ohms, go to step  13). If resistance 5 ohms or more, go to next step.
    INJECTOR DTC 1271-1278 CIRCUIT IDENTIFICATION

    Cylinder No. DTC Low Side Circuit (Wire Color) High Side Circuit (Wire Color)
    1 (1) 1271 555 (Tan) 1087 (Orange)
    2 (2) 1272 556 (White) 878 (Pink/Yellow)
    3 (1) 1273 557 (Brown/Yellow) 1087 (Orange)
    4 (2) 1274 558 (Brown/Light Blue) 878 (Pink/Yellow)
    5 (1) 1275 559 (Tan/Black) 1087 (Orange)
    6 (2) 1276 560 (Light Green/Orange) 878 (Pink/Yellow)
    7 (1) 1277 561 (Tan/Red) 1087 (Orange)
    8 (2) 1278 562 (Light Blue) 878 (Pink/Yellow)
    (1) Right cylinder head.
    (2) Left cylinder head.

  12. 12) Check For Open In Injector

    Remove valve cover. Disconnect suspect injector connector. Measure resistance of high side circuit between injector connector and glow plug injector adapter. Also, measure resistance of low side circuit between injector connector and glow plug injector adapter. If both readings are less than 5 ohms, replace injector. Clear DTCs, and repeat QUICK TEST . If any reading 5 ohms or more, go to step  23).

  13. 13) Check For Open In Low Side Circuit

    Disconnect Injector Driver Module (IDM) 40-pin connector. IDM is located in left side of engine compartment. Measure resistance of suspect low side circuit between wiring harness side of injector connector at valve cover gasket and IDM connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in low side circuit. Clear DTCs, and repeat QUICK TEST .

  14. 14) Check For Open In High Side Circuit

    Measure resistance of suspect high side circuit between wiring harness side of injector connector at valve cover gasket and IDM connector. If resistance is less than 5 ohms, fault may be intermittent. Go to next step. If resistance is 5 ohms or more, repair open in high side circuit. Clear DTCs, and repeat QUICK TEST .

  15. 15) Check For Intermittent Open Injector Circuit

    Ensure IDM is disconnected. Reconnect all other connectors. Connect DVOM between suspect injector low side circuit terminal and high side circuit terminal at IDM wiring harness connector. While observing DVOM, wiggle and bend small sections of wiring harness starting at suspect injector connector and working toward IDM. If resistance changes to more than 5 ohms at any time, isolate fault and repair as necessary. Clear DTCs, and repeat QUICK TEST . If resistance does not change to more than 5 ohms, replace IDM. Clear DTCs, and repeat QUICK TEST .
    16. NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket.

  16. 16) DTC 1291 Or 1292: Check For Short In High Side Circuit
    These DTCs indicate a short to ground or short to power in low side circuit between IDM and fuel injector. Identify DTC and refer to INJECTOR DTC 1291/1292 CIRCUIT IDENTIFICATION  table to determine which circuit to check. Turn ignition off. Disconnect Injector Driver Module (IDM) 40-pin connector. IDM is located in left side of engine compartment. Measure resistance between ground and suspect high side circuit terminal at IDM wiring harness connector. If resistance is more than 10 k/ohms, go to step  18). If resistance is 10 k/ohms or less, go to next step.
    INJECTOR DTC 1291/1292 CIRCUIT IDENTIFICATION

    DTC Circuit No. (Wire Color) Bank
    1291 1087 (Orange) Right
    1292 878 (Pink/Yellow) Left

  17. 17) Check For Short To Ground In High Side Circuit

    Disconnect both injector connectors at appropriate valve cover gasket. Measure resistance between ground and suspect high side circuit terminal at IDM wiring harness connector. If resistance is more than 10 k/ohms, go to step  2). If resistance is 10 k/ohms or less, locate and repair short to ground between IDM connector and injector connector. Clear DTCs, and repeat QUICK TEST .

  18. 18) Check For Short To Power In High Side Circuit

    Turn ignition on. Measure resistance between positive battery terminal and suspect high side circuit terminal at IDM wiring harness connector. Also, measure resistance between positive battery terminal and other high side circuit terminal at IDM wiring harness connector. If both readings are more than 10 k/ohms, fault may be intermittent. Go to next step. If any reading is 10 k/ohms or less, repair short to power in high side circuit. Clear DTCs, and repeat QUICK TEST .

  19. 19) Check For Intermittent Short To Power

    Ensure IDM is disconnected and ignition is on. Connect DVOM between positive battery terminal and suspect injector high side circuit terminal at IDM wiring harness connector. While observing DVOM, wiggle and bend small sections of wiring harness starting at suspect injector connector and working toward IDM. Repeat wiggle test for other injector high side circuit. If resistance changes to less than 10 k/ohms at anytime, isolate fault and repair as necessary. Clear DTCs, and repeat QUICK TEST . If resistance does not change to less than 10 k/ohms, replace IDM. Clear DTCs, and repeat QUICK TEST .
    20. NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket.

  20. 20) DTC 1293-1294: Check For Voltage On High Side Circuit
    These DTCs indicate an open in high side circuit between IDM and fuel injector. Identify DTC and refer to INJECTOR DTC 1293/1294 CIRCUIT IDENTIFICATION  table to determine which circuit to check. Turn ignition off. Disconnect both injector connectors at appropriate valve cover gasket. Turn ignition on. Measure voltage of high side circuit between ground terminal "C" at injector connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step  24).
    INJECTOR DTC 1293/1294 CIRCUIT IDENTIFICATION

    DTC Circuit No. (Wire Color) Bank
    1293 878 (Pink/Yellow) Right
    1294 1087 (Orange) Left

  21. 21) Check Injector Resistance

    Turn ignition off. Install Glow Plug Injector Adapter (014-00935) to suspect injector connector at valve cover gasket. Measure resistance between high side and low side circuit terminals at glow plug injector adapter. If resistance is less than 5 ohms, fault may be intermittent. Go to step  15). If resistance is 5 ohms or more, go to next step.

  22. 22) Check For Open In Wiring Harness

    Remove valve cover. Disconnect suspect injector connector. Measure resistance between injector connector and exterior valve cover gasket connector. If resistance is less than 5 ohms, replace injector. Clear DTCs, and repeat QUICK TEST . If resistance is 5 ohms or more, go to next step.

  23. 23) Determine Wiring Fault

    Disconnect Under Valve Cover (UVC) wiring harness from connector at valve cover gasket. Measure resistance between each terminal in valve cover gasket connector. If all readings are less than 5 ohms, connector is okay. Replace UVC wiring harness. Clear DTCs, and repeat QUICK TEST . If any reading is 5 ohms or more, an open circuit exists in connector. Replace valve gasket. Clear DTCs, and repeat QUICK TEST .

  24. 24) Check For Open In High Side Circuit

    Turn ignition off. Disconnect Injector Driver Module (IDM) 40-pin connector. IDM located on left side of engine compartment. Ensure both injector connectors disconnected at appropriate valve cover gasket. Measure resistance of suspect high side circuit between IDM harness connector and terminal "C" at both suspect injector connectors. If all readings less than 5 ohms, fault may be intermittent. Go to step  15). If any reading 5 ohms or more, locate and repair open in high side circuit. Clear DTCs, and repeat QUICK TEST .
    25. NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket. Each cylinder is tested in numerical sequence (1-8) and does not always set a DTC. It may be necessary to perform KOER CYLINDER CONTRIBUTION SELF-TEST  3 or 4 times to verify that non-contributing cylinder is always the same cylinder.

  25. 25) DTC 0263, 0266, 0269, 0272, 0275, 0278, 0281 Or 0284: Cylinder Non-Contributing
    These DTCs indicate a cylinder is not contributing equally during KOER CYLINDER CONTRIBUTION SELF-TEST . Possible causes for this DTC are:
    • Broken compression rings.
    • Faulty injector assembly.
    • Leaking or bent valve.
    • Bent push rod.
    • Broken rocker arm bolts.
    • Bent connecting rod.

    Perform KOEO SELF-TEST  and KOEO INJECTOR ELECTRICAL SELF-TEST (BUZZ TEST)  under QUICK TEST. Record any continuous DTCs. If any DTCs are set, service DTCs as necessary. Clear DTCs, and repeat QUICK TEST . If no DTCs are set, go to next step.

    CYLINDER CONTRIBUTION DTC IDENTIFICATION

    DTC Cylinder No.
    0263 1
    0266 2
    0269 3
    0272 4
    0275 5
    0266 6
    0281 7
    0284 8

  26. 26) Cylinder Non-Contributing

    Perform TANDEM FUEL PUMP PRESSURE, AIR IN FUEL SYSTEM, LOW IDLE STABILITY and CRANKCASE PRESSURE TEST in ENGINE PERFORMANCE DIAGNOSIS in I - SYSTEM/COMPONENT TESTS - 7.3L DIESEL article. Repair as necessary. Clear DTCs, and repeat QUICK TEST . If no problems are found, check engine mechanical condition. Repair as necessary. If engine mechanical condition is okay, replace injector assembly. Clear DTCs, and repeat QUICK TEST .

  27. 27) DTC 1297: Injector High Side Circuit

    Short Turn ignition off. Disconnect Injector Driver Module (IDM) 40-pin connector. IDM is located in left side of engine compartment. Measure resistance between both high side circuit terminals (No. 23 and 24) at IDM wiring harness connector. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, locate and repair short between high side circuits. Clear DTCs, and repeat QUICK TEST .

  28. 28) Check For Intermittent Between High Side Circuits

    Turn ignition off. Connect DVOM between both high side circuit terminals (No. 23 and 34) at IDM wiring harness connector. While observing DVOM, wiggle and bend small sections of wiring harness starting at IDM connector and working toward injector connectors. If resistance changes to less than 10 k/ohms at anytime, isolate fault and repair as necessary. Clear DTCs, and repeat QUICK TEST . If resistance does not change to less than 10 k/ohms, replace IDM. Clear DTCs, and repeat QUICK TEST .
    29. NOTE: Each valve cover gasket has 2 fuel injector connectors that are part of the gasket. Each connector is responsible for 2 fuel injectors. If connector is faulty, replace valve cover gasket.

  29. 29) DTC 1295 Or 1926: Multiple Concerns
    These DTCs indicate that more than one fault exists on right or left cylinder bank. A short and open on both low side and high side circuits could exist.
    DTC 1295 & 1296 IDENTIFICATION

    DTC Bank
    1295 Right
    1296 Left

    Turn ignition off. Disconnect Injector Driver Module (IDM) 40-pin connector. IDM is located in left side of engine compartment. Measure resistance between ground and each injector circuit terminal at IDM wiring harness connector. If all readings are more than 10 k/ohms, go to next step. If any reading is 10 k/ohms or less, perform the following:

    • If low side circuit short to ground was found, go to step  1). Repair short then return to this step.
    • If high side circuit short to ground was found, go to step  16). Repair short then return to this step.

  30. 30) Check For Short To Power

    Turn ignition on. Measure voltage between positive battery terminal and each injector circuit terminal at IDM wiring harness connector. If all readings are more than 10 k/ohms, go to next step. If any reading is 10 k/ohms or less, perform the following:
    • If low side circuit short to power was found, go to step  6). Repair short then return to this step.
    • If high side circuit short to power was found, go to step  16). Repair short then return to this step.

  31. 31) Check For High Side Circuits Shorted Together

    Turn ignition off. Measure resistance between high side circuit terminals (No. 23 and 24) at IDM wiring harness connectors. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short between high side circuits. Clear DTCs, and repeat QUICK TEST .

  32. 32) Check For Open Circuit

    Disconnect all 4 injector connectors at valve cover gaskets. Measure resistance of all injector high side circuit terminals between valve cover gasket injector connector and IDM wiring harness connector. Also, measure resistance between all low side circuit terminals between valve cover gasket injector connector and IDM wiring harness connector. If all readings are less than 10 k/ohms, go to next step. If any reading is 10 k/ohms or more, repair open in appropriate circuit.

  33. 33) Check For Open Circuit Under Valve Cover

    Install Glow Plug Injector Adapter (014-00935) to a injector connector at valve cover gasket. Measure resistance between high side and low side circuit terminals at glow plug injector adapter. Record resistance. Using glow plug injector adapter, measure resistance between high side and low side circuit terminals at remaining valve cover gasket injector connectors. If any reading is more than 5 ohms, go to step  12). If all readings are 5 ohms or less, reconnect all connectors. Clear DTCs, and repeat KOEO INJECTOR ELECTRICAL SELF-TEST (BUZZ TEST)  and KOEO SELF-TEST  under QUICK TEST. If DTC 1295 or 1296 resets, replace IDM. Clear DTCs, and repeat QUICK TEST .
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