Parts for your 2021 Subaru Impreza-Camshaft sensor

2021 Subaru Impreza Camshaft Sensor: What it does and how to look after it

Yes, the 2021 Subaru Impreza is fitted with camshaft position sensors. Technical references that confirm this include the Subaru Factory Service Manual for the FB20 engine used in the 2021 Impreza (Engine Diagnostics section citing DTCs P0340/P0345 for the camshaft position sensor circuit), Subaru Technical Information System wiring diagrams showing the Camshaft Position (CMP) sensor inputs to the Engine Control Module, and Subaru literature describing AVCS (Active Valve Control System) operation, which relies on camshaft position feedback. Put simply, the Impreza’s engine management won’t do its job properly without the cam sensors.

The camshaft sensor’s purpose is to tell the ECU exactly where the camshaft is in its rotation. Paired with the crankshaft sensor, it synchronises fuel injection and ignition timing, and lets the AVCS adjust valve timing on the fly for better torque, efficiency, and lower emissions. It’s crucial for clean cold starts, smooth idle, and strong mid‑range pull—pretty much the brains behind how tidy the FB20 runs.

There’s no scheduled replacement interval for the camshaft sensor—it’s a solid‑state component that’s replaced only if faulty. As part of regular servicing, it’s smart to visually check the connector and loom under the bonnet for oil seepage, brittle insulation, or chafing, especially near the timing cover and cylinder head where heat and vibration live. If the Check Engine light pops up with codes like P0340 or P0345, or the car has hard starting, rough idle, hesitation, or poor fuel economy, a scan‑tool diagnosis of live cam/crank correlation is the next step.

• Keep connectors clean and seated, use dielectric grease sparingly on the seal if advised by the service manual.
• If removing the sensor, replace the O‑ring to prevent oil leaks and torque the retaining bolt to spec.
• Use quality OEM‑equivalent parts—cheap units can cause intermittent sync issues.

Replacement is typically straightforward: the sensor is mounted to the cylinder head and held by a single bolt. With the battery disconnected and access cleared, a careful swap, O‑ring refresh, and a post‑repair scan to clear fault codes is usually all that’s needed. A workshop will also confirm the cam/crank sync and valve timing targets to be sure AVCS control is behaving as it should. Look after the wiring, fix oil leaks promptly, and the cam sensor should go the distance across plenty of Kiwi and Aussie kilometres.

Popular questions about 2021 Subaru Impreza camshaft sensors

Does the 2021 Impreza have one or two camshaft sensors?
Most 2021 Impreza FB20 engines use two camshaft position sensors monitoring the intake camshafts—one per cylinder bank on the boxer engine. This gives the ECU accurate feedback for sequential injection and AVCS control. Always verify by VIN if ordering parts, as regional specs can vary.

Is it safe to drive with a failing camshaft sensor?
The car may run, but starting, power, and fuel economy can suffer, and it may stall or enter limp mode. Driving for long with a dodgy sensor risks catalyst damage from misfires. Best bet: have it scanned and sorted promptly.

When should the camshaft sensor be replaced?
There’s no routine interval—replace only if it’s faulty. During regular services, inspect the wiring and check for leaks. If faults like P0340/P0345 appear, confirm with diagnostics before replacement.