P0300 on a 2017 Jeep Grand Cherokee
P0300 is a generic OBD2 powertrain code for random or multiple cylinder misfire. Unlike P0301 through P0308, it does not point to one specific cylinder, so the cause can be ignition, fuel, air, sensor, or mechanical.
Not your vehicle? See general P0300 info.
Most common causes on the 2017 Jeep Grand Cherokee
Ranked from 361 NHTSA owner complaints filed for this vehicle.
- 1
Worn or Damaged Camshaft / Lifters / Rocker Arms
High severityThe 3.6L Pentastar engine is known for premature wear or failure of rocker arms and lifters, which damages the camshaft and causes ticking noises, misfires, and engine failure.
Reported in 3 NHTSA complaints - 2
Blown Head Gasket / Cylinder Head Failure
High severityCylinder head warping or head gasket failure can cause coolant leaks, overheating, white smoke from the exhaust, and severe misfires.
Reported in 3 NHTSA complaints - 3
Faulty Ignition Coils / Spark Plugs
Medium severityWorn or failing ignition coils and spark plugs are a primary cause of misfires. Look for rough idle, stalling, and specific cylinder misfire codes alongside P0300.
Reported in 2 NHTSA complaints - 4
Fuel Pump / Fuel Delivery System Failure
High severityA failing fuel pump or fuel module prevents adequate fuel pressure, leading to lean misfires, stalling, or a no-start condition.
Reported in 1 NHTSA complaint - 5
Vacuum Leak / Intake Manifold Leak
Medium severityUnmetered air entering the engine throws off the air/fuel ratio, causing random misfires. Confirmed by lean codes and smoke testing.
Common cause - 6
Faulty Fuel Injectors
Medium severityClogged or failing fuel injectors prevent proper fuel atomization, leading to misfires. Confirmed by injector flow testing or moving the injector to see if the misfire follows.
Common cause - 7
Low Engine Compression
High severityInternal engine wear, such as bad piston rings or burnt valves, leads to a loss of compression and subsequent misfires. Confirmed by a compression or leak-down test.
Common cause - 8
Faulty Mass Air Flow (MAF) or MAP Sensor
Low severityIncorrect air density readings cause the PCM to deliver the wrong amount of fuel, resulting in random misfires across multiple cylinders.
Common cause
These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0300 on your car still needs shop confirmation before any repair.
Common symptoms
- Flashing or steady check engine light
- Rough idle
- Shaking under acceleration
- Loss of power
- Fuel smell from exhaust
What to check before replacing parts
Scan for cylinder-specific misfire codes
Look for: A companion P0301–P0308 pins the misfire to one cylinder — start there. P0300 with no cylinder code points at something hitting several at once: fuel pressure, a large vacuum leak, or timing.
Inspect the spark plugs and coils
Look for: Pull the plugs: black/sooty = rich, oily = oil intrusion, white/blistered = lean or overheating, cracked porcelain or an out-of-spec gap = replace. Then swap a coil to another cylinder — if a cylinder-specific code follows the coil, the coil is bad.
Check fuel trims for a vacuum leak
Look for: High positive short- and long-term trims (worst at idle, improving as RPM rises) mean unmetered air is getting in. Smoke-test the intake and listen for hissing.
Verify fuel pressure
Look for: Compare running/cranking pressure to the vehicle spec. Low or dropping pressure starves multiple cylinders and reads as a random misfire — suspect the pump, filter, or regulator.
Compression / leak-down test if ignition and fuel check out
Look for: A cylinder 15%+ below the others, or leak-down hissing from the intake (intake valve), exhaust (exhaust valve), or oil filler (rings), means the misfire is mechanical — not a swap-in part.
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