Misfire · Diagnostic trouble code

P0300

Random / multiple cylinder misfire detected

What it means

In plain terms

The engine control module counted misfires but could not pin them to a single cylinder. Either several are missing, or the pattern moves around.

What sets it

The trigger condition

Crankshaft speed variation crosses the misfire threshold across more than one cylinder inside the monitor’s sample window.

Generic SAE definition. Manufacturers extend and sometimes override these, so the enhanced code on the vehicle in front of you may be narrower than what is written here.

Common causes

6 things that set P0300.

This is the list every other P0300 page will give you. Read it, then read the part underneath it.

What P0300 gives you
  • Vacuum leak affecting every cylinder on the bank
  • Fuel delivery: weak pump, restricted filter, or failing regulator
  • Ignition system wear across the set: plugs, wires, coil pack
  • EGR flowing when it should not be
  • Low compression across multiple cylinders
  • Contaminated or wrong-octane fuel
6 candidates · no ranking · your call
What AceDx gives you
One ranked call
Named specifically enough to order the part, with a confidence number and the evidence printed underneath.
1 call · evidence attached · you can overrule it
A frequency ranking is about every vehicle that ever threw P0300. You are working on one of them.
The actual problem

That list is not a diagnosis. It is a to-do list you did not ask for.

Every one of those 6 causes is now a decision somebody in the bay has to make, under a clock, on a car a customer wants back today.

We haven’t published a verdict for P0300 yet.

We could mock one up. We’re not going to. A fabricated example of our own product’s output is exactly the kind of thing this page is criticizing. Verdicts appear here as the pilot produces them on real vehicles, with the evidence they actually stood on.

Related codes

What often shows up beside it.

All diagnostic trouble codes →

Stop working P0300 from a list.

The pilot runs on your existing scan tool and your live repair orders. Bring us a car that's throwing this code.