P0300 on a 2019 Chevrolet Malibu
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 2019 Chevrolet Malibu
Ranked from 188 NHTSA owner complaints filed for this vehicle.
- 1
Brake Vacuum Pump Failure (causing internal engine damage)
High severityThe brake vacuum pump breaks apart internally, sending metal debris into the engine which damages the camshaft and timing chain, leading to misfires and engine failure.
Reported in 6 NHTSA complaints - 2
Throttle Body / Charge-Air Hose Disconnection
High severityThe charge-air hose blows off the throttle body due to missing or failed retention clips/gaskets under turbo pressure, causing sudden loss of power, stalling, and misfires.
Reported in 4 NHTSA complaints - 3
Faulty Engine Control Module (ECM) / Body Control Module (BCM)
High severityElectrical failures within the ECM or BCM cause erratic engine behavior, stalling, and misfires.
Reported in 2 NHTSA complaints - 4
Camshaft Position Sensor / Actuator Failure
Medium severityFaulty camshaft sensors or actuators disrupt engine timing, leading to poor performance, stalling, and misfire codes.
Reported in 2 NHTSA complaints - 5
Faulty Fuel Injectors
Medium severityFuel injectors fail to inject fuel properly, leading to a lean condition, failure to start, and random misfires.
Reported in 1 NHTSA complaint - 6
Worn Spark Plugs
Low severitySpark plugs wear out over time, causing weak or absent spark which leads to incomplete combustion and random misfires.
Common cause - 7
Faulty Ignition Coils
Medium severityIgnition coils degrade and fail to provide sufficient voltage to the spark plugs, resulting in misfires across multiple cylinders.
Common cause - 8
Vacuum Leaks
Medium severityUnmetered air enters the intake manifold, causing a lean air-fuel mixture that results in random misfires.
Common cause
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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