How to Diagnose a Cherokee Bad Crank Position Sensor

The crank position sensor in a Jeep Cherokee is designed to record information about the revolutions per minute (rpm) and relative position of the crankshaft. The crank position sensor sends this information to the engine control unit (ECU). The ECU processes this information and uses it to manage the Cherokee's engine. When the crank sensor goes bad, the ECU can't determine when to fire the ignition, resulting in an inability to start the engine. An automotive scan tool must be used to determine whether the crank sensor is bad or another component is at fault.

Things You'll Need

  • Automotive scan tool

Instructions

    • 1

      Shut down the engine and depress the parking brake. Shift the Cherokee's transmission into park or first gear (manual transmission).

    • 2

      Locate the diagnostic data port underneath the dashboard on the driver's side of the vehicle. Connect an automotive scan tool to this port and power on the tool.

    • 3

      Select "ECU" from the scan tools primary menu, then select "Live Data" from the scan tool's secondary menu. Select "CKP Sensor."

    • 4

      Turn the ignition to the "START" position and crank the engine. Watch the scan tool to see if it displays the cranking rpm of the engine on the crank sensor live data screen. If it does not display the cranking rpm then the crank position sensor is bad and must be replaced.

Tips & Warnings

  • Automotive scan tools are portable computers that connect to vehicles to run tests and gather information. They are available from auto parts stores and automotive tool retailers.
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