P0300 on a 2015 Dodge Durango
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 Durango
Ranked from 502 NHTSA owner complaints filed for this vehicle.
- 1
Rocker arm / valve-lifter wear (3.6L Pentastar 'ticking' failure) causing cylinder misfire
High severityA large cluster of owners report the well-known Pentastar rocker-arm/roller-follower wear (audible ticking), with several confirming an active misfire code (P0302, P0306) traced to worn rockers/camshaft lobes rather than ignition or fuel parts.
Reported in 14 NHTSA complaints - 2
Ignition coil / spark plug failure
Medium severityOne owner replaced the coil pack and spark plugs on the misfiring cylinder as the standard first diagnostic step before the injector and ultimately valve-train wear were implicated.
Reported in 1 NHTSA complaint - 3
Worn engine/motor mounts inducing a wiring-related misfire
Low severityOne owner's engine misfire was diagnosed and treated as failed motor mounts, though it recurred after replacement — mount wear lets the engine move enough to chafe coil/injector wiring.
Reported in 1 NHTSA complaintParts:engine mount - 4
Fuel delivery interruption from a failing fuel pump relay/TIPM
Low severityA reported loss of motive power traced to a defective fuel pump relay can starve one or more cylinders long enough to register a misfire before stalling.
Reported in 1 NHTSA complaintParts:fuel pump relay - 5
Vacuum or intake leak
Medium severityUnmetered air entering the intake leans out a cylinder enough to misfire.
Common cause - 6
Clogged or leaking fuel injector
Medium severityA partially clogged or dribbling injector starves or floods a cylinder.
Common causeParts:fuel injector - 7
Carbon-fouled intake valves
Low severityCarbon buildup disrupts valve sealing/airflow enough to misfire.
Common cause - 8
EGR valve stuck open
Low severityExcess recirculated exhaust gas dilutes the intake charge enough to misfire at idle/low load.
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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