P0300 on a 2015 Chevrolet Suburban 1500
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 Chevrolet Suburban 1500
Ranked from 428 NHTSA owner complaints filed for this vehicle.
- 1
Collapsed/failed AFM lifters (5.3L V8 Active Fuel Management)
High severityExtremely well-documented failure on this generation 5.3L: a cylinder-deactivation lifter collapses, that cylinder loses valve lift/compression, and the engine sets a misfire/limp-mode code; several owners on this exact truck had lifters replaced, in some cases more than once.
Reported in 7 NHTSA complaints - 2
Worn or fouled spark plugs
Low severityOne repair order for this truck listed spark plug replacement alongside code P0300; oil-fouled or worn plugs are a top misfire cause on this engine.
Reported in 1 NHTSA complaintParts:spark plug - 3
Failing ignition coil
Medium severityReplaced alongside spark plugs and injectors on this truck's P0300 repair; a weak coil produces an intermittent, load-sensitive misfire on one or more cylinders.
Reported in 1 NHTSA complaintParts:ignition coil - 4
Clogged or leaking fuel injector
Medium severityAll 8 injectors were replaced on this truck when P0300 set; a dirty or leaking injector starves or floods a cylinder and produces a misfire.
Reported in 1 NHTSA complaintParts:fuel injector - 5
Vacuum leak (intake/PCV hose)
Medium severityUnmetered air entering downstream of the MAF leans out one or more cylinders enough to misfire at idle; smoke-test the intake boots and PCV lines.
Common cause - 6
Carbon-fouled intake valves
Low severityCarbon buildup on valve stems/seats disrupts airflow and sealing on individual cylinders, common on higher-mileage GM V8s.
Common cause - 7
Low cylinder compression (worn rings/valves)
High severityRules out electrical causes; a compression test isolates a mechanically weak cylinder from an ignition or fuel-delivery misfire.
Common cause - 8
EGR valve stuck open
Low severityExcess exhaust gas recirculated at idle/light load dilutes the intake charge enough to cause a rough, misfire-like idle.
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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