Worn or fouled spark plugs (most common on turbocharged and high-mileage Subaru engines); Faulty ignition coil or coil pack on the affected cylinder; Vacuum leak from intake gaskets, hoses, or the PCV system causing a lean misfire; Clogged or failing fuel injector restricting fuel delivery; Low fuel pressure from a weak pump or clogged filter; Mechanical issues such as low compression, valve problems, or a head gasket leak; Exhaust restriction or a failing catalytic converter that raises backpressure and temperature

DTC codes / Subaru codes / P1301

P1301 · SubaruFire Due To Increased Exhaust Temperature

Q: What does code P1301 mean?

Fire Due To Increased Exhaust Temperature. P1301 on Subaru vehicles indicates the engine control module (ECM) has detected a misfire condition severe enough to raise exhaust gas temperatures to a dangerous level, typically by monitoring crankshaft speed fluctuations and comparing them to expected values. The ECM sets this code when the misfire rate exceeds a threshold that could overheat and damage the catalytic converter or exhaust components.

P1301 on Subaru vehicles indicates the engine control module (ECM) has detected a misfire condition severe enough to raise exhaust gas temperatures to a dangerous level, typically by monitoring crankshaft speed fluctuations and comparing them to expected values. The ECM sets this code when the misfire rate exceeds a threshold that could overheat and damage the catalytic converter or exhaust components.

SystemPowertrain

Code typeSubaru specific

SeverityHigh

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Check engine light illuminated, often flashing if the misfire is severe
Noticeable engine shaking or rough idle, especially when cold
Loss of power or hesitation during acceleration
Poor fuel economy due to incomplete combustion
A sulfur or rotten egg smell from the exhaust in some cases
Often no symptoms besides the warning light if the misfire is intermittent

Common causes, most likely first

Worn or fouled spark plugs (most common on turbocharged and high-mileage Subaru engines)
Faulty ignition coil or coil pack on the affected cylinder
Vacuum leak from intake gaskets, hoses, or the PCV system causing a lean misfire
Clogged or failing fuel injector restricting fuel delivery
Low fuel pressure from a weak pump or clogged filter
Mechanical issues such as low compression, valve problems, or a head gasket leak
Exhaust restriction or a failing catalytic converter that raises backpressure and temperature

How to diagnose and fix it

Scan all stored and pending codes with an OBD-II scanner to identify which cylinder(s) are misfiring and check freeze-frame data
Inspect spark plugs for wear, gap, and fouling; replace them if they are due or show damage
Swap ignition coils between cylinders to see if the misfire moves, confirming a faulty coil
Perform a propane or smoke test to check for vacuum leaks around intake gaskets and hoses
Test fuel injectors for resistance and spray pattern, and check fuel pressure with a gauge
Run a compression test and cylinder leak-down test to rule out mechanical faults
Check exhaust backpressure with a pressure gauge to ensure the catalytic converter is not restricted

Why P1301 Often Points to Ignition

On Subaru boxer engines, the spark plug wells can collect oil from leaking tube seals, causing misfires that set P1301 without any other codes.
A flashing check engine light with P1301 means the misfire is actively dumping raw fuel into the exhaust, which can melt the catalytic converter in minutes; stop driving immediately.
Many technicians replace the catalytic converter first because of the 'exhaust temperature' wording, but the converter is usually the victim, not the cause.
Subaru's ECM can set P1301 for a misfire that is too subtle to feel, so a scan tool with live misfire counters is essential for diagnosis.
A dirty mass airflow sensor (MAF) or a failing front oxygen sensor can skew fuel trims and create a lean misfire that triggers P1301 without any ignition component being faulty.

Can I keep driving with P1301?

If the check engine light is flashing, stop driving as soon as it is safe to do so to prevent catalytic converter damage. If the light is steady and the engine runs smoothly, you may drive cautiously to a repair shop, but avoid hard acceleration and towing.

Tools that help

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Guidance is general and written for Subaru vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.