P0300 on a 2020 Jeep Wrangler
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 2020 Jeep Wrangler
Ranked from 597 NHTSA owner complaints filed for this vehicle.
- 1
Camshaft, rocker arm, or lifter (valvetrain) failure
High severityMultiple owners report a misfire confirmed by metal shavings in the oil, cam/rocker-arm/tappet failure, or bad cams described by dealers as a common problem across many Wranglers -- a well-known valvetrain wear pattern on this generation.
Reported in 5 NHTSA complaints - 2
Low compression from overheating-related engine damage
High severityOne owner's engine lost compression and locked up right after an unwarned thermostat overheating event on the highway.
Reported in 1 NHTSA complaint - 3
Worn or fouled spark plugs
Low severityAged or carbon-fouled plugs weaken spark and are the most common source of a random multi-cylinder misfire on any gasoline engine.
Common causeParts:spark plugs - 4
Failing ignition coil
Medium severityA weakening individual coil produces a repeatable misfire on the cylinder it fires, worsening under load.
Common causeParts:ignition coil - 5
Vacuum or intake air leak
Low severityUnmetered air leaning a cylinder's mixture is a classic random-misfire cause, especially noticeable at idle.
Common cause - 6
Clogged or leaking fuel injector
Medium severityAn injector delivering too little or too much fuel to one cylinder produces a repeatable misfire on that cylinder.
Common causeParts:fuel injectors - 7
EGR valve stuck open
Low severityExcess recirculated exhaust gas dilutes the intake charge enough to cause misfire at idle or light throttle.
Common causeParts:EGR valve
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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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