2000 Jeep Grand Cherokee P0300-P0306 Misfire Causes: Worn Plugs, Injectors, or Cam Sensor?

Worn spark plugs or faulty plug wires are common causes of misfires in the 2000 Jeep Grand Cherokee. Additionally, dirty fuel injectors can contribute to cylinder misfiring. Start with a basic maintenance routine: replace oil, air, and fuel filters; perform an oil change; install new spark plugs and plug wires; and add one bottle of Techron to a full tank of gasoline. This often resolves the issue in vehicles that haven't had recent service.

Check fuel pressure first. Gently pinch the return line—if pressure increases to at least the specified rail pressure, the fuel pressure regulator is faulty. If pressure remains low, inspect the fuel filter for blockage. If the issue persists, consider a weak fuel pump, insufficient voltage to the pump, or a restricted fuel supply line. Proper diagnosis begins here.

It's possible that the dealership pressure-washed the engine before delivery, which could have damaged internal components. Misfires across all six cylinders are unusual if only spark plug wear is involved. If the car runs fine otherwise, try clearing the codes and monitoring for recurrence—this may indicate a temporary issue or intermittent fault.

The 2000 Jeep Grand Cherokee 4.0L V6 uses a camshaft position (CMP) sensor instead of a traditional distributor to trigger the coil-on-plug system. The Powertrain Control Module (PCM) relies on this sensor to activate each of three coils that fire the six spark plugs. P0300 indicates a random misfire, while P0301–P0306 specify individual cylinder misfires. Chrysler vehicles from this era had known issues with camshaft position sensors seizing due to internal wear. As the sensor shaft dries out and binds, it can cause the PCM to incorrectly trigger coil ignition—leading to a perceived misfire and setting primary circuit codes like P0351, P0352, or P0353. If your vehicle shows these specific cylinder misfire codes but no P035x codes, the cam sensor may still be failing. If such codes are present, replacing the camshaft position sensor is recommended. If not, further diagnostics should be performed to identify other root causes. Robert Grove, Two Brothers Automotive Consulting — ASE Certified Triple Master, CA Smog Technician, Advanced Emissions Instructor (Orange County). Visit: http://www.twobrothersauto.com

Has anyone since found a resolution or updated their diagnosis? Any new test results or repair outcomes?

I have the same issue on my 2000 Jeep Grand Cherokee. I've replaced the crankshaft sensor, spark plugs, ignition rail, and all associated components. After extensive work, I believe the root cause is a faulty engine control module (PCM). Since it's not my vehicle but my father’s, he has also sent it for similar repairs.

The PCM is unlikely to be the source of this issue. Focus instead on wiring connections near the engine block, particularly around the head bolt studs. Always purchase a crankshaft position sensor from an authorized dealer—using aftermarket parts can lead to misdiagnosis or failure. While distributor issues may cause similar codes, they are not typically linked to P0300–P0306 in this model; wiring faults or sensor degradation are more likely culprits.