The crankshaft position sensor in a Subaru Legacy is a critical engine management component that provides the engine control unit (ECU) with real-time data on crankshaft angle and speed. This information is essential for precise fuel injection timing, ignition spark control, and variable valve timing operation. When the sensor begins to fail, common symptoms include intermittent stalling, rough idle, extended cranking before starting, and sometimes a check engine light with codes such as P0335 or P0336. Locating the sensor accurately is the first step in diagnosis or replacement. Because the Legacy has been produced across multiple generations with different engine families (EJ, EZ, FA, FB), the sensor’s position varies. This comprehensive guide covers the typical locations, required tools, step-by-step identification procedures, and troubleshooting tips for all major Subaru Legacy model years.

Understanding the Crankshaft Position Sensor in a Subaru Legacy

The crankshaft position sensor (CPS) in a Subaru Legacy is typically a magnetic or Hall-effect sensor that reads a toothed reluctor ring mounted on the crankshaft or the flywheel. On Subaru’s horizontally opposed (boxer) engines, the sensor is usually mounted through the engine block or timing cover, pointed at a ring with 36-2 or 36-1 teeth pattern. The sensor must maintain an air gap of approximately 0.5–1.5 mm between its tip and the reluctor teeth. Any contamination, damage, or misalignment can cause signal loss, leading to misfires or no-start conditions.

On Subaru Legacy engines, the CPS may be paired or integrated with the camshaft position sensor for synchronisation, but it always retains a distinct physical location. Understanding the engine family in your specific Legacy helps narrow down the search. The EJ series (found in Legacy models up to about 2009) often places the CPS near the front of the engine; the FA/FB series (from 2010 onward) tends to locate it near the oil pan or timing chain cover on the passenger side. The EZ six-cylinder engines (for H6 Legacy models) have the sensor mounted on the front of the block, close to the crankshaft pulley.

General Location Across Subaru Legacy Generations

The Subaru Legacy has spanned seven generations (1990–present). While early models share common EJ22/EJ25 engine mounting, later generations introduced the FA20 and FB25 engines with timing chains instead of belts. Below is a breakdown by generation.

First and Second Generation (1990–1999)

These Legacy models were equipped with the EJ22 or EJ25 engine, and the crankshaft position sensor is mounted on the front of the engine, behind the timing belt cover. The sensor is threaded into the block just above the crankshaft sprocket. To access it, you must remove the serpentine belt, the crankshaft pulley, and the timing belt covers. The electrical connector is a two-pin weatherpack style and is located on the passenger side (right side of the engine) near the front. No need to remove the entire timing belt unless you are performing a full replacement – simply unbolt the sensor from its boss.

On turbocharged Legacy models (e.g., Legacy GT), the CPS location is identical, but you may need to remove the intercooler air ducting to get a clear view. Always clean the area around the sensor before removal to prevent debris from falling into the timing cover.

Third and Fourth Generation (2000–2009)

These Legacy generations introduced the EZ30 six-cylinder and later evolved the EJ25 with variable valve timing (AVCS). For EJ engines, the crankshaft position sensor remains near the front, behind the timing belt cover, similar to the earlier models. However, some 2005–2009 models with the EJ253 engine (non-turbo) have the sensor relocated to the lower right side of the engine block, adjacent to the oil pan. This variation is due to a revised reluctor ring design. You can identify it by following the main engine harness from the ECU down towards the passenger side of the block near the starter motor area.

For the EZ30 H6 engine, the sensor is mounted on the front of the engine, just above the crankshaft pulley, underneath the intake manifold plenum. Access requires removal of the air filter box and the plastic intake duct. The sensor is secured by a single 10mm bolt; its electrical connector points toward the radiator.

Fifth and Sixth Generation (2010–2019)

These models began the transition to FA20 and FB25 engines with timing chains. On the FA20 (used in Legacy models like the 2.0 GT but more common in the Forester/Impreza, the Legacy used the FB25 from 2013 onward), the crankshaft position sensor is located on the passenger side of the engine block, low down, just behind the alternator and above the oil pan. It is bolted to the block with a single 10mm head bolt. The sensor tip faces a reluctor wheel that is integrated into the crankshaft web. Access from the top is challenging; it is easier to work from underneath the vehicle after removing the splash shield.

On the sixth generation (2015–2019), the FB25 engine continues with the same location. Some owners report that the sensor is partially hidden by the wiring harness for the knock sensor. Carefully move the harness aside to see the two-pin connector. The sensor body is black plastic and has a rectangular mounting flange.

Seventh Generation (2020–Present)

The current Legacy (2020+), offered with the FB25 or FA24 turbo (Legacy XT), carries a similar sensor placement. The sensor is located on the front (nose) of the engine, on the passenger side, at the junction between the timing chain cover and the oil pan. It is accessible from above after removing the engine cover (the large plastic cover over the engine). You will see a small black component with a two-pin connector pointing forward. A single 10mm bolt secures it to the timing chain cover. The air gap is preset, so the sensor simply bolts in place with no adjustment. For the FA24 turbo, the sensor is slightly higher because of the turbo oil and coolant lines, but the location is essentially the same.

Step-by-Step Guide to Locating the Crankshaft Position Sensor

The following procedure applies to most Subaru Legacy models with the EJ25 or FB25 engine. Always consult your vehicle’s service manual for torque specifications and specific connector locations.

Safety Precautions

  • Park the vehicle on a level surface and engage the parking brake.
  • Allow the engine to cool completely (hot surfaces can cause burns).
  • Disconnect the negative battery terminal and wait at least 10 minutes for the airbag system capacitors to discharge.
  • Wear safety glasses and mechanic’s gloves.
  • Use jack stands if you need to get under the vehicle – never rely on a jack alone.

Tools You Will Need

  • 10mm socket with an extension (most CPS bolts are 10mm, some are 8mm – a 1/4-inch drive ratchet is handy)
  • Flathead screwdriver (for prying connectors if stuck)
  • Flashlight or work light
  • Trim removal tools (to remove clips and plastic covers without breaking them)
  • Replacement CPS (if replacing) – use OEM (22690-AA001 or equivalent) for best reliability
  • Dielectric grease (for the connector pins)

Locating the Sensor: Step-by-Step

  1. Remove the engine cover: For 2000s-era Legacys, lift the plastic cover off the engine. For newer models, pry up at the rubber grommets. Set the cover aside.
  2. Identify the front of the engine: The crankshaft pulley is at the front of the engine. The sensor will be somewhere on the passenger side of the block, usually within 12 inches of the pulley.
  3. Inspect behind the alternator: On many FB25 and FA20 engines, the CPS sits just behind the alternator bracket. Look for a two-wire connector coming off the engine harness that goes to a small black or grey plastic component.
  4. Check near the oil pan: On some EJ engines (2005–2009), the sensor is lower, almost level with the oil pan flange. Use a flashlight to look from underneath the passenger side of the engine.
  5. Use a service manual or online diagrams: If you are unsure, search for “Subaru Legacy crankshaft position sensor location” with your engine code (e.g., EJ25 or FB25). Many hobbyists share clear photos on forums and repair sites.
  6. Verify by unbolting one bolt: Once you think you have found the sensor, trace the wiring 1–2 inches back to see if it goes to a two-pin connector. Unbolt the sensor carefully – if it is the CPS, you will see a long cylindrical tip (approximately 1–1.5 inches long).

If you cannot see the sensor from the top, you will need access from underneath. Remove the plastic under-engine splash shield (held by 10mm bolts and push clips). Then look toward the front of the oil pan on the passenger side. The CPS may be secured horizontally into the side of the block.

Common Mistakes When Trying to Find the CPS

  • Confusing it with the knock sensor: The knock sensor on Subaru engines is typically located near the top of the block, between the cylinder heads, with a single wire. The CPS is lower and always has two wires (signal and ground).
  • Looking only at the front of the engine: Some Subaru Legacy models have the sensor on the rear side of the engine block (near the flywheel). This is less common but does appear on certain automatic transmission configurations. Check the rear of the engine near the bell housing.
  • Assuming all EJ engines are the same: The EJ253 vs. EJ255 turbo have different sensor placements due to the higher-mounted turbo. For EJ255/257 (Legacy GT), the sensor is still front-mounted but hidden by the turbo inlet duct.
  • Not disconnecting the battery: If you accidentally short the sensor signal wire to ground while the engine is running, it can damage the ECU.

When to Replace the CPS and How to Test It

If you have found the sensor and suspect it is faulty, you can perform a few checks before buying a replacement. The most reliable diagnostic is to read the live data stream with an OBD2 scan tool while cranking the engine. The CPS should show a reading (e.g., 500–800 RPM when cranking or a voltage pulse pattern). If the scan tool shows 0 RPM and the engine will not start, the CPS or its wiring is likely the issue. Visually inspect the sensor tip for metal shavings or debris. Clean it with a lint-free cloth and reinstall. The air gap is not adjustable on most Subaru sensors; the mounting bracket ensures proper clearance.

Replace the sensor if you see physical damage, corrosion on the connector pins, or if the engine runs better after unplugging and reconnecting the sensor (indicating an intermittent electrical contact). Always use a genuine Subaru sensor or a high-quality aftermarket unit from a reputable brand like Denso, Hitachi, or NTK. Cheap aftermarket sensors often fail prematurely or give incorrect signals.

Conclusion

Locating the crankshaft position sensor in a Subaru Legacy requires knowledge of the engine generation and a methodical approach. Whether your Legacy is a 1996 EJ22 or a 2022 FB25, the sensor will be found near the crankshaft – either at the front of the engine behind the timing cover, on the passenger side of the block above the oil pan, or occasionally near the flywheel. Using the guidelines above, you should be able to visually identify the sensor within minutes. Remember to gather proper tools, follow safety precautions, and consult your vehicle’s service manual for torque specs. With the sensor located, you can proceed confidently with testing or replacement, restoring your Legacy’s smooth running and reliable starting.

For further assistance, check Subaru’s Official Owner Resources for model-specific diagrams, or refer to repair guides from trusted Subaru enthusiast forums (verify accuracy with your year). When purchasing a replacement, consider professional-grade parts from RockAuto’s Subaru selection.