Contaminated or failed mass air flow sensor element; Intake air leak between the MAF sensor and the throttle body; Damaged or corroded MAF sensor wiring or connector; Clogged or improperly installed air filter element; Faulty engine control module (ECM) or poor ECM ground; Restricted exhaust or intake tract causing low airflow readings; Aftermarket oiled air filter over-oiling the MAF element

DTC codes / Subaru codes / P1142

P1142 · SubaruMass Air Flow Sensor Circuit Low Input

Q: What does code P1142 mean?

Mass Air Flow Sensor Circuit Low Input. P1142 on a Subaru means the engine control module (ECM) has detected a mass air flow (MAF) sensor signal that is lower than the expected range for the current operating conditions. The ECM compares the MAF voltage against a calculated airflow model and flags this code when the actual reading stays below the minimum threshold for a set period.

P1142 on a Subaru means the engine control module (ECM) has detected a mass air flow (MAF) sensor signal that is lower than the expected range for the current operating conditions. The ECM compares the MAF voltage against a calculated airflow model and flags this code when the actual reading stays below the minimum threshold for a set period.

SystemPowertrain

Code typeSubaru specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other symptoms
Rough idle or stalling shortly after startup
Hesitation or stumble during acceleration
Reduced engine power and poor throttle response
Occasional lean misfire codes or a flashing check engine light under load
Poor fuel economy or black smoke from the tailpipe in severe cases

Common causes, most likely first

Contaminated or failed mass air flow sensor element
Intake air leak between the MAF sensor and the throttle body
Damaged or corroded MAF sensor wiring or connector
Clogged or improperly installed air filter element
Faulty engine control module (ECM) or poor ECM ground
Restricted exhaust or intake tract causing low airflow readings
Aftermarket oiled air filter over-oiling the MAF element

How to diagnose and fix it

Inspect the air intake tract for cracks, loose clamps, or disconnected hoses between the MAF sensor and throttle body
Check the MAF sensor connector for corrosion, bent pins, or loose terminals and repair as needed
Clean the MAF sensor element with a dedicated MAF cleaner and recheck live data
Verify the air filter is correct, clean, and properly seated in the airbox
Backprobe the MAF sensor signal wire and compare voltage to the manufacturer's specification at idle and under load
Perform a smoke test on the intake system to locate hidden vacuum or boost leaks
Replace the MAF sensor only after confirming wiring integrity and ruling out intake leaks

Before you replace the MAF sensor

A dirty MAF sensor element from an over-oiled aftermarket air filter is one of the most common causes of P1142 on Subaru engines, and cleaning often resolves the code without parts replacement.
An intake leak downstream of the MAF sensor lets unmetered air into the engine, which can mimic a low MAF signal and set P1142 even when the sensor itself is healthy.
Corroded or chafed wiring near the MAF connector is frequently overlooked because the sensor tests fine on a bench but the signal is lost through a poor connection.
P1142 does not always mean the MAF sensor has failed; a restricted air filter or collapsed intake hose can reduce airflow enough to trigger the low input threshold.
Subaru ECMs are sensitive to MAF sensor voltage, so a sensor that reads only slightly low at idle can still set P1142 during steady cruise conditions.

Can I keep driving with P1142?

You can usually drive the vehicle to a repair shop, but avoid hard acceleration and heavy loads because a low MAF signal can cause lean running and misfires. If the check engine light flashes or the engine stalls repeatedly, stop driving and arrange a tow.

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.