P0300 on a 2017 Chrysler Pacifica

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 2017 Chrysler Pacifica

Ranked from 1,484 NHTSA owner complaints filed for this vehicle.

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1
Cylinder head gasket failure / coolant intrusion into a cylinder
High severity
Well-documented 3.6L Pentastar issue on this generation Pacifica: coolant leaks past the head gasket (or a warped/cracked head) into a cylinder, fouling the plug and causing a persistent misfire (often coded as a specific-cylinder P030x alongside the P0300); confirm with a coolant loss with no external leak, white exhaust smoke, or a positive cylinder leak-down/compression test.
Reported in 9 NHTSA complaints
Parts:head gasket cylinder head
2
Worn or fouled spark plugs
Medium severity
Standard high-mileage wear item; several owners reported spark plugs replaced as part of misfire diagnosis on this vehicle. Look for excessive gap, carbon fouling, or coolant/oil deposits on the electrode.
Reported in 4 NHTSA complaints
Parts:spark plugs
3
Failing ignition coil(s)
Medium severity
Coil-on-plug failure produces a weak or absent spark on one or more cylinders; owners on this vehicle replaced coils during misfire troubleshooting. Confirm by swapping a coil to another cylinder and watching the misfire follow it.
Reported in 2 NHTSA complaints
Parts:ignition coil
4
Vacuum or intake leak
Medium severity
Unmetered air entering after the MAF causes lean misfire, most often at idle; check intake boots, PCV hose, and brake booster line with smoke test.
Common cause
5
Clogged or leaking fuel injector(s)
Medium severity
A partially clogged or dribbling injector disrupts the air/fuel ratio on that cylinder; check injector balance/flow rates and spray pattern.
Common cause
Parts:fuel injector
6
Carbon-fouled intake valves
Low severity
Direct/port injection buildup on valve backs disrupts airflow and atomization, contributing to random misfire, especially at idle and low RPM.
Common cause
7
Low cylinder compression (worn rings or valves)
Medium severity
Mechanical wear reduces cylinder sealing; a compression or leak-down test isolates this from ignition/fuel causes and often correlates with the head gasket/head warpage failures reported on this engine.
Common cause
8
EGR valve or passage fault
Low severity
A stuck-open EGR valve or clogged passage upsets combustion at idle/light load, producing an intermittent misfire; test EGR flow and inspect the valve for carbon sticking.
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