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Home >> Jeep >> 2009 >> Grand Cherokee Laredo, 3.0 M, RWD >> Repair and Diagnosis >> Engine Performance >> System >> DTCS P0675 To P2002 - Diesel >> P1200-Multiple Injector Failure Detected >> Diagnostic Test

Diagnostic Test

  1. CHECK FOR ACTIVE DTC 
    NOTE: If the ECM detects and stores a DTC, the ECM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed.
    NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for an active DTC.
    1. With the scan tool, erase ECM DTCs.
    2. Test drive the vehicle and attempt to duplicate the problem.
    3. With the scan tool, read ECM DTC's.

      Did this DTC set again?

      Yes 

      • Go to step  2

      No 

  2. INJECTOR QUANTITY ADJUSTMENT 
    NOTE: Each Fuel Injector is labeled with a code. This code determines the injector quantity adjustment. Each Injector code must be programmed into the ECM using the scan tool.
    1. Turn the ignition off.
    2. Refer to the Service Information to locate each fuel injector label and check for the correct code for each fuel injector in the ECM.

      Are all of the injector codes correct?

      Yes 

      • Go to step  3

      No 

  3. CYLINDER FUEL QUANTITY CORRECTION 
    1. With the scan tool, perform the Cylinder Fuel Quantity Correction Test.

      Is each Cylinder within specifications?

      Yes 

      • Go to step  4

      No 

  4. FUEL INJECTOR HIGH-SIDE CONTROL CIRCUIT SHORTED TO VOLTAGE 
    1. Turn the ignition off.
    2. Disconnect each Fuel Injector harness connector.
    3. Disconnect the Engine Control Module (ECM) harness connector.
    4. Remove the ASD Relay from the PDC.
    5. Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay Connector.
    6. Turn the ignition on.
    7. Measure the voltage of each Fuel Injector High-Side Control circuit in each Fuel Injector harness connector.

      Is there voltage present on any of the High-Side Control circuits?

      Yes 

      No 

      • Go to step  5
  5. FUEL INJECTOR LOW-SIDE CONTROL CIRCUIT SHORTED TO VOLTAGE 
    NOTE: The jumper wire should still be in place.
    1. Measure the voltage of each Fuel Injector Low-Side Control circuit in each Fuel Injector harness connector.

      Is there voltage present on any of the Low-Side Control circuits?

      Yes 

      No 

      • Go to step  6
  6. FUEL INJECTOR HIGH-SIDE CONTROL CIRCUIT SHORTED TO GROUND 
    1. Turn the ignition off.
    2. Remove the jumper wire and install the ASD relay.
    3. Measure the resistance between ground and each Fuel Injector High-Side Control circuit in each Fuel Injector harness connector.

      Is the resistance above 1000 ohms for each Fuel Injector High-Side Control circuits?

      Yes 

      • Go to step  7

      No 

  7. FUEL INJECTOR LOW-SIDE CONTROL CIRCUIT SHORTED TO GROUND 
    1. Measure the resistance between ground and each Fuel Injector Low-Side Control circuit in each Fuel Injector harness connector.

      Is the resistance above 1000 ohms for each Fuel Injector Low-Side Control circuits?

      Yes 

      • Go to step  8

      No 

  8. FUEL INJECTOR HIGH-SIDE CONTROL CIRCUIT SHORTED TO FUEL INJECTOR LOW-SIDE CONTROL CIRCUIT 
    1. Measure the resistance between each Fuel Injector High-Side Control circuit and each Fuel Injector Low-Side Control circuit in each Fuel Injector harness connector.

      Is the resistance above 1000 ohms for each Fuel Injector?

      Yes 

      • Go to step  9

      No 

  9. FUEL INJECTOR HIGH-SIDE CONTROL CIRCUIT OPEN OR HIGH RESISTANCE 
    1. Measure the resistance of each Fuel Injector High-Side Control circuit between each Fuel Injector harness connector and the Engine Control Module (ECM) harness connector.

      Is the resistance below 10.0 ohms for each Fuel Injector High-Side Control circuit?

      Yes 

      • Go to step  10

      No 

  10. FUEL INJECTOR LOW-SIDE CONTROL CIRCUIT OPEN OR HIGH RESISTANCE 
    1. Measure the resistance of each Fuel Injector Low-Side Control circuit between each Fuel Injector harness connector and the Engine Control Module (ECM) harness connector.

      Is the resistance below 10.0 ohms for each Fuel Injector Low-Side Control circuit?

      Yes 

      • Go to step  11

      No 

  11. FUEL INJECTOR 
    1. Measure the resistance between the terminals of each Fuel Injector.

      Is the resistance approximately 185k ohms (+/- 10%) for each Injector?

      Yes 

      • Go to step  12

      No 

  12. ENGINE CONTROL MODULE (ECM) 
    1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between each Fuel Injector and the Engine Control Module (ECM).
    • Look for any chafed, pierced, pinched, or partially broken wires.
    • Look for broken, bent, pushed out or corroded terminals.
    • Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
    • Look for the data to change or for the DTC to reset during the wiggle test.
    • Check for any Technical Service Bulletins that may apply.