Diagnostic Test

2009 Jeep Grand Cherokee Laredo, 3.7 K, RWDSECTION Diagnostic Test
  1. CHECK FOR ACTIVE DTC 
    1. With the scan tool, read the active DTCs.
    2. Cycle the ignition switch from off to on, leaving the ignition on for a minimum of 10 seconds then turn the ignition off.
    3. With the scan tool, read the active DTCs.

      Does the scan tool display this DTC as active?

      Yes 

      • Go to step  2

      No 

  2. DETERMINE ENGINE SIZE 

    Is this vehicle equipped with a 3.7L or 6.1L engine?

    Yes 

    • Go to step  3

    No 

    • Go to step  6
  3. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT SHORTED TO VOLTAGE 
    Fig 1: Checking Fused Ignition Switch Output (Run Start) Circuit Shorted To Voltage
    GC0120161Courtesy of CHRYSLER LLC
    1. Disconnect the Shift Lever Assembly harness connector.
    2. Cycle the ignition switch from off to on then back to off.
      NOTE: The ignition switch must be in the off position when performing the following step.
    3. Using a 12-volt test light connected to ground, check the (F1) Fused Ignition Switch Output (Run Start) circuit.

      Does the test light illuminate brightly?

      Yes 

      No 

      • Go to step  4
  4. SHIFT LEVER ASSEMBLY 
    Fig 2: Checking Shift Lever Assembly
    GC0120162Courtesy of CHRYSLER LLC
    1. Turn the ignition on.
    2. With the test light still connected from the previous step, check the (F1) Fused Ignition Switch Output (Run Start) circuit.

      Does the test light illuminate brightly?

      Yes 

      No 

      • Go to step  5
  5. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT OPEN 
    Fig 3: Checking Fused Ignition Switch Output (Run Start) Circuit Open
    GC0120163Courtesy of CHRYSLER LLC
    1. Turn the ignition off.
    2. Remove the FCM from the Integrated Power Module.
    3. Measure the resistance of the (F1) Fused Ignition Switch Output (Run Start) circuit between the Shift Lever Assembly and the FCM-IPM connector.

      Is the resistance below 5.0 ohms?

      Yes 

      No 

  6. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT SHORTED TO VOLTAGE 
    Fig 4: Checking Fused Ignition Switch Output (Run Start) Circuit Shorted To Voltage
    GC0120164Courtesy of CHRYSLER LLC
    1. Disconnect the Powertrain Control Module C1 harness connector.
      CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.
    2. Cycle the ignition switch from off to on then back to off.
      NOTE: The ignition switch must be in the off position when performing the following step.
    3. Using a 12-volt test light connected to ground, check the (F1) Fused Ignition Switch Output (Run Start) circuit.

      Does the test light illuminate brightly?

      Yes 

      No 

      • Go to step  7
  7. POWERTRAIN CONTROL MODULE 
    Fig 5: Checking Powertrain Control Module
    GC0120165Courtesy of CHRYSLER LLC
    1. Turn the ignition on.
    2. With the test light still connected from the previous step, check the (F1) Fused Ignition Switch Output (Run Start) circuit.
      CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.

      Does the test light illuminate brightly?

      Yes 

      No 

      • Go to step  8
  8. (F1) FUSED IGNITION SWITCH OUTPUT (RUN START) CIRCUIT OPEN 
    Fig 6: Checking Fused Ignition Switch Output (Run Start) Circuit Open
    GC0120166Courtesy of CHRYSLER LLC
    1. Turn the ignition off.
    2. Remove the FCM from the Integrated Power Module.
      CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.
    3. Measure the resistance of the (F1) Fused Ignition Switch Output (Run Start) circuit between the Powertrain Control Module C1 connector and the FCM-IPM connector.

      Is the resistance below 5.0 ohms?

      Yes 

      No 

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.