Parts for your 2018 Subaru Impreza-Camshaft sensor

2018 Subaru Impreza camshaft sensor: what it does, and when to replace it

Technical documentation confirms the 2018 Subaru Impreza is fitted with camshaft position sensors. The Subaru Service Manual for 2018MY Impreza (FB engine) includes diagnosis for DTCs P0340/P0345 (Camshaft Position Sensor Circuit), and the Subaru Electronic Parts Catalogue lists “Sensor Assembly – Camshaft Position” for the FB20 engine on both left‑hand and right‑hand cylinder heads. Those sources establish the camshaft sensor is relevant and used on this model.

On the 2018 Impreza’s FB20 engine, the camshaft sensor tracks the exact position and speed of the camshaft(s) so the ECU can sync fuel injection, ignition timing, and the Active Valve Control System (AVCS). That accurate timing is what gives smooth starts, clean idle, decent fuel economy, and snappy throttle response. The Impreza uses two camshaft sensors—one per bank—so the ECU always knows where each intake cam sits relative to the crankshaft.

This isn’t a scheduled service item, it’s generally fit‑and‑forget. However, age, heat, oil contamination, or wiring issues can cause dramas. When a sensor or its circuit plays up, owners may notice harder starting (especially warm restarts), rough idle, hesitation under load, reduced fuel economy, and the Check Engine Light. Scan tools will commonly show codes such as P0340/P0345/P0341/P0346.

Basic care goes a long way. Keep to regular oil changes with the spec the factory calls for—clean oil helps AVCS components behave, which reduces false cam correlation faults. Under the bonnet, check the sensor connectors and harness routing for rubbing or brittle insulation, and fix any oil weeps that could wick into plugs.

Replacement is straightforward for a competent tech. Usual steps include disconnecting the battery, unclipping the sensor connector on the front/top of each cylinder head, removing the retaining bolt, and easing out the sensor and O‑ring. A light film of clean engine oil on the new O‑ring helps installation. Bolt it in, torque to the service‑manual spec, reconnect, clear codes, and perform a road test. If a fault persists, further checks of wiring continuity, cam timing, AVCS oil control valves, and ECM data are wise before condemning parts.

Quality matters—genuine or reputable aftermarket sensors tend to give reliable signal quality. Mixing and matching unknown parts can invite intermittent faults that are a headache to chase. For most owners, the best plan is simple: watch for symptoms, keep the engine serviced on time, and sort any warning lights promptly.

• Replace the sensor if there are relevant fault codes, confirmed bad waveforms, or obvious damage.
• Always address wiring/connectors and oil leaks at the same time to avoid repeat issues.

How many camshaft sensors does a 2018 Subaru Impreza have, and where are they?

The FB20 engine uses two camshaft position sensors—one on each cylinder head. They’re mounted near the front/top of the heads by the timing cover area, with easy access once engine covers are off.

Do camshaft sensors need regular servicing or cleaning?

No scheduled servicing is required. They’re sealed electronic sensors. Practical care is about keeping connectors clean and dry, ensuring engine oil is changed on time, and fixing any oil leaks that might contaminate plugs.

Is it safe to drive with a faulty camshaft sensor?

The engine will often run, but it may start poorly, feel sluggish, and use more fuel, it can also stall at idle. It’s best to have it diagnosed and repaired soon rather than pushing on, especially before long trips.