Faulty exhaust temperature sensor (sensor element degraded or failed); Damaged or corroded wiring or connector at the sensor; Open or short circuit in the sensor circuit; Exhaust leaks before the sensor causing false temperature readings; Engine control module software issue or internal fault (less common); Catalytic converter overheating or restriction affecting sensor readings

DTC codes / Subaru codes / P1312

P1312 · SubaruExhaust Temperature Sensor Malfunction

Q: What does code P1312 mean?

Exhaust Temperature Sensor Malfunction. P1312 on Subaru vehicles indicates that the engine control module has detected an abnormal signal from the exhaust temperature sensor, which is used to monitor the temperature of the exhaust stream near the catalytic converter. The computer compares the sensor's output against expected values and flags the code when the signal is out of range, erratic, or absent.

P1312 on Subaru vehicles indicates that the engine control module has detected an abnormal signal from the exhaust temperature sensor, which is used to monitor the temperature of the exhaust stream near the catalytic converter. The computer compares the sensor's output against expected values and flags the code when the signal is out of range, erratic, or absent.

SystemPowertrain

Code typeSubaru specific

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine performance or power, especially under load
Poor fuel economy due to the engine control module entering a protective mode
Rough idle or hesitation during acceleration in some cases
In rare instances, the engine may enter limp mode limiting speed

Common causes, most likely first

Faulty exhaust temperature sensor (sensor element degraded or failed)
Damaged or corroded wiring or connector at the sensor
Open or short circuit in the sensor circuit
Exhaust leaks before the sensor causing false temperature readings
Engine control module software issue or internal fault (less common)
Catalytic converter overheating or restriction affecting sensor readings

How to diagnose and fix it

Connect a scan tool and verify P1312 is active, then check for related codes and freeze-frame data
Visually inspect the exhaust temperature sensor and its wiring for damage, corrosion, or loose connections
Measure the sensor's resistance and compare to Subaru specifications for the current temperature
Check for exhaust leaks upstream of the sensor that could skew readings
Test the sensor circuit for opens, shorts, or high resistance with a multimeter
Replace the exhaust temperature sensor if tests indicate it is faulty
Clear the code and perform a road test to confirm the repair, monitoring live data

Exhaust Temperature Sensor Diagnosis Nuances

A P1312 code can be set by a sensor that is slow to respond rather than completely dead, so live data graphing during warm-up is more revealing than a simple resistance check.
Exhaust leaks before the sensor are a commonly overlooked cause because they allow outside air to cool the sensor tip, producing a signal that seems plausible but is out of range.
On some Subaru models, the exhaust temperature sensor is used to protect the catalytic converter from overheating, so a code may appear only during sustained high-load driving.
Replacing the sensor without checking the circuit can lead to a repeat failure if the real problem is chafed wiring near the exhaust manifold.
A P1312 code does not always mean the sensor itself is bad; the engine control module's internal bias voltage can be faulty, though this is rare.

Can I keep driving with P1312?

You can usually continue driving with P1312, but avoid sustained high-speed or heavy-load driving because the engine control module may not be able to protect the catalytic converter from overheating. Have the fault diagnosed soon to prevent potential damage to the exhaust system.

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.