P0300 on a 2015 Chrysler Town And Country
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 Chrysler Town And Country
Ranked from 381 NHTSA owner complaints filed for this vehicle.
- 1
Worn camshaft lobes / defective rocker arm-lifter assembly (3.6L Pentastar)
High severityA well-known defect on this engine: worn cam lobes and failing rocker arm/lifter assemblies produce a ticking noise, cylinder misfires, and can eventually cause the engine to stall or seize; diagnosed by independent mechanics on multiple owners' vehicles.
Reported in 4 NHTSA complaints - 2
Failing fuel injector(s)
Medium severityOwners had specific-cylinder misfires (cylinder 1, cylinder 3) traced to and resolved (temporarily) by fuel injector replacement.
Reported in 2 NHTSA complaintsParts:fuel injector - 3
Valve or valve-seat leak causing compression loss
High severityOwners had a leaking intake valve seat and a compression leak diagnosed on cylinders showing chronic misfires, requiring head removal/machining to correct.
Reported in 2 NHTSA complaints - 4
Spark plug failure (cracked insulator)
High severityOne owner's persistent cylinder-3 misfire was ultimately traced to a spark plug with a cracked insulator that later failed catastrophically and cracked the cylinder head.
Reported in 1 NHTSA complaintParts:spark plug - 5
Coolant intrusion into a cylinder via failed oil cooler/oil filter housing seal
High severityOne owner found antifreeze mixed into a piston chamber, traced to the plastic oil filter adapter (OFA)/oil cooler seal failure common on this engine; coolant entering a cylinder will foul combustion and misfire.
Reported in 1 NHTSA complaint - 6
Vacuum or intake leak
Medium severityUnmetered air entering after the MAF leans out one or more cylinders, especially at idle.
Common cause - 7
Carbon-fouled intake valves
Low severityCarbon buildup on valves disrupts airflow and atomization; common at higher mileage.
Common cause - 8
EGR valve or passage fault
Low severityA stuck-open EGR valve dilutes the intake charge enough to 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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