P0300 on a 2015 Dodge Journey
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 2015 Dodge Journey
Ranked from 548 NHTSA owner complaints filed for this vehicle.
- 1
Low compression from worn cylinder/valve components
High severityOne complaint documents a mechanic-confirmed cylinder-6 misfire with low compression and cylinder head damage; another describes a connecting-rod failure/blown engine, both consistent with severe internal wear causing misfire.
Reported in 2 NHTSA complaintsParts:cylinder head gasket - 2
Oil fouling from an oil filter housing/cooler leak
Low severityTwo complaints describe a cracking plastic oil filter housing/cooler leaking oil onto the engine, which can foul plugs/connectors and contribute to misfire.
Reported in 2 NHTSA complaintsParts:oil filter housing - 3
Failing ignition coil
High severityOne complaint has an explicit misfire diagnosis (cylinder 3, bad coil) with the coil replaced but the misfire recurring, pointing to a coil or its harness/connector.
Reported in 1 NHTSA complaintParts:ignition coil - 4
Worn spark plugs and/or head gasket wear (recurring cylinder misfire)
High severityOne owner reports a recurring cylinder-2 misfire with spark plugs and gaskets replaced twice over 5 years without a permanent fix, consistent with plug wear compounded by a sealing issue.
Reported in 1 NHTSA complaint - 5
3.6L Pentastar engine-specific misfire defect
Medium severityOne owner explicitly describes continual misfiring and power loss tied to a known 3.6L Pentastar engine issue that Chrysler recalled on earlier model years.
Reported in 1 NHTSA complaint - 6
Rocker arm / valve lifter wear (2.4L engine top end)
Medium severityOne complaint cites faulty rocker arms and lifters from manufacturing defects, a known top-end wear pattern on Chrysler's 2.4L engine that can produce valvetrain noise and misfire.
Reported in 1 NHTSA complaint - 7
Moisture-related ignition component failure (plug wires/coil boots)
Medium severityOne owner reports unexplained idle misfires that worsen in rain or ahead of rain, a classic symptom of arcing spark plug wires or coil boots letting in moisture.
Reported in 1 NHTSA complaint - 8
Vacuum leak
Low severityUnmetered air entering the intake leans out one or more cylinders enough to misfire, particularly at idle.
Common cause - 9
Clogged or leaking fuel injector
Low severityA partially clogged or dribbling injector under- or over-fuels a cylinder, producing an intermittent misfire.
Common causeParts:fuel injector
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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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