P0301 on a Toyota

Researched from the OBD-II standards and published manufacturer specifications

Quick answer

On Toyota 2AZ-FE engines documented for oil consumption, a cylinder 1 misfire can result from oil-fouled spark plugs on that specific cylinder, though which cylinder is affected first varies by individual engine wear pattern.

Severity 3 of 4. Short trips only.

Fix now · Short trips only

P0301 on a Toyota, at a glance
CodeP0301
Standard nameCylinder 1 Misfire Detected
MakeToyota
SeverityFix now (3 of 4)
Safe to driveShort trips only
Tool neededScanner with live data
Reads P0301: live data and freeze frame

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Adds live sensor streams and freeze frame, which is what turns a code into a diagnosis rather than a guess.

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Coverage varies by tool and by model year, so check a specific tool against a specific vehicle before buying.

What is different about P0301 on a Toyota?

The same 2AZ-FE oil consumption pattern documented for random misfire codes can just as easily isolate to a single cylinder like cylinder 1 depending on which cylinder is consuming the most oil.

Toyota specific patterns behind P0301

Cylinder-specific oil fouling: On the documented 2AZ-FE engine used in many 2007 to 2009 Camry and RAV4 models, oil consumption does not necessarily affect every cylinder evenly, and a spark plug fouled by oil in the cylinder 1 position specifically is a documented cause of an isolated P0301 code.

Ignition coil failure specific to one cylinder: Outside of the documented oil consumption pattern, a single failing ignition coil remains a common and generic cause of a cylinder-specific misfire code on Toyota engines generally.

What to check first on a Toyota

The order below narrows the generic P0301 list down to what is worth checking first on this make. It is a starting order, not a diagnosis: patterns are generation specific and a vehicle outside those generations may have none of them.

Check in this order

  • Inspect the cylinder 1 spark plug for oil fouling if the engine is a documented 2AZ-FE from the affected years
  • Swap the cylinder 1 ignition coil with another cylinder's coil to see if the misfire follows the coil
  • Check cylinder 1 spark plug condition and gap generally
  • Check for a vacuum leak local to that cylinder's intake runner

The generic picture behind P0301

The computer counts tiny fluctuations in crankshaft speed between firing events and attributes each misfire to the cylinder whose firing position lines up with the disturbance. This code sets when that pattern repeatedly points to cylinder 1 specifically, rather than being spread across the engine. A single cylinder misfire almost always traces back to something local to that cylinder, such as its plug, coil or injector.

Everything on the main P0301 page still applies here. This page narrows the cause list to the patterns documented on Toyota vehicles, it does not replace the underlying definition.

The generic version of this code

Tools that can diagnose P0301

Adds live sensor streams and freeze frame, which is what turns a code into a diagnosis rather than a guess.

Common questions

Can oil consumption affect only one cylinder on a Toyota?

Yes, oil consumption on the documented 2AZ-FE engine does not necessarily affect every cylinder evenly, so a spark plug fouled by oil in one specific cylinder position, including cylinder 1, is a documented cause of a cylinder-isolated misfire code rather than a random one.

Which cylinder is cylinder 1 on a Toyota four-cylinder engine?

Cylinder numbering can vary by specific engine, though it is commonly numbered from the timing chain or belt end. Check a cylinder numbering diagram for your exact engine to be certain rather than assuming.

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