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P0300

P0300 on a 2019 Ram 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 2019 Ram 1500

Ranked from 1,449 NHTSA owner complaints filed for this vehicle.

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  1. 1

    eTorque Motor Generator Unit (MGU) / Alternator failure

    High severity

    Failure of the eTorque MGU causes severe voltage drops, battery discharge, and engine stalling. Low voltage can easily trigger random misfires (P0300) before the engine completely shuts down.

    Reported in 7 NHTSA complaints
  2. 2

    Cracked exhaust manifolds / broken manifold bolts

    Medium severity

    Cracked exhaust manifolds or broken bolts cause exhaust leaks, which can throw off O2 sensor readings and lead to a random misfire code. Multiple complaints cite cracked manifolds and exhaust leaks.

    Reported in 5 NHTSA complaints
  3. 3

    Camshaft and lifter failure (Hemi tick)

    High severity

    The 5.7L Hemi engine is known for lifter failure that damages the camshaft, causing a misfire (P0300) and a ticking noise. The complaints mention ticking noises, misfires, and metal shavings in the oil system.

    Reported in 3 NHTSA complaints
  4. 4

    Faulty spark plugs or ignition coils

    Medium severity

    Worn spark plugs or failing ignition coils are the most common generic causes of a P0300 random misfire code. They fail to ignite the air/fuel mixture properly.

    Common cause
  5. 5

    Vacuum leak / Intake manifold leak

    Medium severity

    Unmetered air entering the engine leans out the air/fuel mixture, causing random misfires across multiple cylinders.

    Common cause
  6. 6

    Fuel delivery issue (low fuel pressure, failing fuel pump, or clogged injectors)

    Medium severity

    Inadequate fuel pressure or clogged injectors prevent the proper air/fuel mixture, leading to 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

1

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.

2

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.

3

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.

4

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.

5

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 RoughFlashing Check Engine Light