Parts for your 2009 Subaru Legacy-Camshaft sensor

2009 Subaru Legacy camshaft sensor — what it does and how to look after it

Based on Subaru’s factory service manual for the 2009 Legacy/Outback (BL/BP series), the Subaru FAST parts catalogue, and OEM supplier listings (Hitachi/Denso), the 2009 Subaru Legacy is fitted with camshaft position sensor(s). The 2.5i with the EJ253 engine typically uses one sensor, while models with DOHC and variable valve timing (like many EJ255 2.5T and the EZ30 H6) use a sensor on each bank. So yes, a camshaft sensor is relevant on this model year and is part of normal diagnostics and servicing considerations.

On a 2009 Subaru Legacy, the camshaft sensor lets the engine control unit know exactly where the cam is in its rotation. That info is crucial for clean starts, smooth idle, proper spark timing, sequential fuel injection, and (on AVCS-equipped engines) accurate variable valve timing control. If the signal goes missing or messy, the ECU can’t sync fuel and spark properly, which can lead to long crank times, rough running, and average-as fuel economy.

It’s not a scheduled replacement item, but it does deserve attention whenever the vehicle is serviced—especially as kilometres climb. A quick visual once-over of the sensor body, O-ring, and wiring plug is smart: Subaru engines can weep a little oil with age, and oil-soaked connectors or hardened O-rings can cause intermittent faults. Keeping the connector clean and the harness properly clipped away from heat and moving bits goes a long way.

Common warning signs include a Check Engine light with codes like P0340/P0341, hard starting when warm, misfires at low revs, or the car dropping into a limp-like mode on AVCS cars. Before replacing, confirm good battery voltage, check the connector pins for spread or corrosion, and inspect the timing belt/chain and cam target if other symptoms suggest mechanical timing issues.

When replacement is needed, use an OEM or reputable-brand sensor. Disconnect the battery, unplug the connector, remove the retaining bolt, and ease the sensor out so the O-ring isn’t nicked. Lightly oil the new O-ring, seat it square, and tighten the bolt to the factory spec—don’t overdo it. Clear codes, start the engine, and verify stable cam and crank sync with a scan tool if available. Done right, a fresh sensor can restore crisp starts and smoother running, and keep the Legacy happy on long Kiwi and Aussie road trips.

• Watch for: hard starts, uneven idle, flat spots, AVCS performance drop, and fault codes P0340/P0341.
• Service tip: inspect connector and O-ring at each major service, keep wiring secure and clean.
• Parts choice: stick with OEM-equivalent for reliable signal quality and proper fit.

Popular questions about 2009 Subaru Legacy camshaft sensors

Where is the camshaft sensor located on a 2009 Legacy?
On most EJ253 2.5i models, it’s mounted on the left-hand cylinder head near the front of the engine. On DOHC/AVCS engines (e.g., many EJ255 turbos) and the EZ30 H6, there’s a sensor on each bank—look near the front or rear of each head, depending on variant. Access often involves simple hand tools and a bit of room around the timing cover area.

Do camshaft sensors need routine replacement?
No. They’re replaced on condition. If the car starts cleanly, idles well, and shows no related fault codes, it can keep running the original sensor for years. Prioritise inspection: check the plug for oil or moisture, make sure the harness is secure, and only swap the sensor if diagnostics confirm it’s the culprit.

What symptoms point to a failing camshaft sensor?
Expect extended cranking, stumbling idle, random stalls, poorer fuel economy, and codes like P0340/P0341. On AVCS-equipped models, you may feel lazy low-end response or see timing targets not being met on a scan tool. Always verify power, ground, and signal integrity before condemning the sensor.