P0300 on a 2022 Jeep Wrangler Unlimited Phev

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 2022 Jeep Wrangler Unlimited Phev

Ranked from 371 NHTSA owner complaints filed for this vehicle.

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1
Fuel injector or fuel-delivery fault
Medium severity
One owner had a failed fuel injector and high-pressure fuel pump replaced, then found fuel still improperly entering the engine, consistent with an injector/delivery problem that would misfire a cylinder.
Reported in 1 NHTSA complaint
Parts:fuel injector fuel pump
2
Weak fuel pump / fuel starvation causing stall-related misfire
Medium severity
Fuel pump failure left the vehicle stranded and unable to accelerate, a pattern consistent with fuel-starvation misfire.
Reported in 1 NHTSA complaint
Parts:fuel pump
3
Worn or fouled spark plugs
Low severity
Standard high-mileage misfire cause; check for eroded electrodes or carbon fouling with plugs pulled.
Common cause
Parts:spark plug
4
Failing ignition coil(s)
Medium severity
Swap-test a suspect coil to a known-good cylinder; misfire following the coil confirms it.
Common cause
Parts:ignition coil
5
Carbon-fouled intake valves from frequent short engine-run cycles
Low severity
PHEVs cycle the gas engine on/off often in hybrid mode, which promotes carbon buildup on direct-injection intake valves that disrupts airflow/combustion.
Common cause
6
Vacuum or intake air leak
Medium severity
Look for a hissing sound and unmetered air entering after the MAF/throttle body; causes lean misfire especially at idle.
Common cause
7
Low cylinder compression (worn rings/valves)
High severity
A compression or leak-down test isolates a mechanical cause behind a persistent misfire.
Common cause
8
EGR valve stuck open or malfunctioning
Medium severity
Excess exhaust gas recirculated at idle/low load can destabilize combustion and set a misfire code.
Common cause
Parts: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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Matching symptoms

Car Runs Rough Flashing Check Engine Light