P0346 Code: Subaru Impreza (2017-2023) - Causes, Symptoms & Fixes

Below is a comprehensive diagnostic guide for OBD-II code P0346 on the 2017–2023 Subaru Impreza. This guide uses the provided NHTSA data (no owner complaints and no recalls found for this make/model/year/issue) and combines general automotive knowledge with model-typical specifics for Subaru flat-four engines. Data limitations are noted where relevant.

CODE MEANING AND SEVERITY

• Code: P0346
• Full description (generic): Camshaft Position Sensor A Circuit Range/Performance (Bank 2)
• What it means for the Impreza: The Powertrain Control Module (PCM) detected a fault in the camshaft position sensor circuit for the Bank 2 cam sensor (signal, reference voltage, or ground) and the sensor signal is outside expected range or not consistent with engine RPM.
• Severity and behavior: Depending on the vehicle, P0346 can cause rough running, misfires, poor acceleration, or difficulty starting. In some cases the engine may stall or fail to start. A stored P0346 often lights the MIL (Check Engine Light). Because cam timing information is critical for ignition timing and fuel injection, this DTC can impact drivability but may not always trigger a limp mode unless accompanied by other codes.
• Important note for Subaru Impreza: Subaru engines in the 2017–2023 Impreza are typically FA-series 2.0L DOHC boxer engines with two banks of cams. P0346 refers to the Bank 2 cam sensor circuit (A). Bank 1 is the other side; bank numbering depends on engine layout. Treat P0346 as a cam sensor circuit fault on the Bank 2 side unless a service document specifies otherwise for your exact engine variant.

COMMON CAUSES ON SUBARU IMPREZA

• Faulty Bank 2 Camshaft Position Sensor A (sensor failure)
• Damaged or corroded wiring harness or connector to the Bank 2 cam sensor (insulation wear, broken traces, loose plugs)
• Poor or loose sensor ground or 5V reference circuit from the PCM
• Oil contamination or oil starvation near the Bank 2 cam sensor (oil leaks, sludge, or excessive engine oil pressure affecting the sensor)
• Timing-related issues (timing chain/belt wear, stretched chain, worn tensioner or guides) causing the cam timing to drift relative to crankshaft position; the PCM then sees an out-of-range cam signal
• Variable Valve Timing (VVT) solenoid failure or oil passages restricted, indirectly affecting cam timing reference signals
• PCM/ECU fault or software calibration mismatch (less common, but possible)
• Intermittent electrical fault (loose connector, moisture, or vibration-induced disconnect)

SYMPTOMS (typical for P0346 in this vehicle)

• MIL illumination with a stored P0346 code
• Rough idle or misfires on one or more cylinders
• Hesitation or lack of power during acceleration
• Difficulty starting or intermittent no-start condition
• Engine runs but may stall under load
• Possible degraded fuel economy
• In some cases, no obvious drivability symptoms aside from the MIL

DIAGNOSTIC STEPS (practical, maintenance-friendly workflow)

Note: Begin with the least invasive checks and progress to more involved tests. If you’re not comfortable with timing assessments, seek professional help early.

Step 1 – Verify the code and scan for related codes

• Use a capable OBD-II scanner to confirm P0346 and note any related codes (P0340, P0345, P0341, P0335, P0336, P0335 may accompany cam or crank sensor issues).
• Check freeze-frame data (engine speed, load, temp, etc.) at the time the code set.

Step 2 – Visual inspection of Bank 2 cam sensor and wiring

• Locate the Bank 2 Cam Position Sensor A. Inspect the sensor and its connector for oil leaks, dirt, corrosion, or damaged plastic.
• Inspect the wiring harness for exposed conductors, chafed insulation, pin corrosion, or loose/poorly seated connectors. Wiggle the connector while monitoring the data to detect intermittent faults.
• Check for oil contamination around the sensor area; clean any oil residue and address leaks.

Step 3 – Check electrical continuity and voltage

• With the ignition off, disconnect the Bank 2 CMP sensor connector and test the wire harness for continuity to the PCM (signal, 5V reference, and ground as applicable). Compare to the schematic or a known-good reference.
• Reconnect and perform a voltage check with the ignition on (engine off) to verify the 5V reference is present and the ground is solid.
• When the engine is cranking, monitor the CMP signal wire with a multimeter or oscilloscope to see if a clean, periodic waveform is present. A flaky or erratic signal supports a sensor or wiring fault rather than a purely mechanical timing issue.

Step 4 – Check sensor operation and reference signals

• If your tool or oscilloscope shows a weak or irregular Bank 2 CMP A signal, consider replacing the cam sensor as a test/repair.
• If the sensor and wiring test OK, proceed to Step 5.

Step 5 – Inspect cam timing and related components (timing mechanism)

• If there are symptoms of timing drift (misalignment of timing marks, a timing chain slack, or abnormal engine timing indicators), inspect the timing chain/belt, tensioner, guides, and sprockets for wear or slack.
• Subaru engines with DOHC timing chains may require timing chain inspection if a sensor fault test inconclusive. Mechanical timing issues can trigger P0346-like signals.
• If timing components are suspect, this is a more invasive repair and may require specialist service.

Step 6 – Check VVT system and oil condition

• A clogged or restricted VVT oil passages or a faulty VVT solenoid can alter cam timing signals. Inspect and test the VVT solenoid operation and oil pressure/flow.
• Check oil quality and level. Low oil or dirty oil can affect cam phasing and sensor readings. Change oil if due and monitor.

Step 7 – Clear codes and perform a recheck / drive cycle

• After you perform a repair or service, clear the codes and run a complete drive cycle to confirm that P0346 does not return. Re-check with a scan tool after a few driving cycles.

Step 8 – If the code persists

• If the Bank 2 CMP sensor and wiring test clean but the code remains, the issue may be ECU-related or timing-mechanism-related. Consider professional diagnosis, including a thorough timing inspection and possible PCM reprogramming or replacement if indicated.

RELATED CODES

• P0340 – Camshaft Position Sensor Circuit Malfunction (Bank 1 or general, depending on hardware)
• P0341 – Camshaft Position Sensor Circuit Range/Performance (Bank 1)
• P0345 – Camshaft Position Sensor Circuit Range/Performance (Bank 2)
• P0342, P0343, P0344, P0347 – Other cam sensor circuit variants or misalignment signals
• P0335 – Crankshaft Position Sensor A Circuit Malfunction (often checked in conjunction with cam sensor codes)

REPAIR OPTIONS AND COSTS (2025 prices)

Note: Actual prices vary by region, shop, parts choice (OEM vs. aftermarket), and whether timing components are involved. The following ranges reflect common market costs.

• Bank 2 Camshaft Position Sensor A replacement (sensor only)

  • Parts: typically $20–$150
  • Labor: about 0.5–1.5 hours
  • Estimated total: $100–$400

• Bank 2 CMP sensor wiring repair or connector replacement

  • Parts: $10–$80 (connector/insulation or harness repair)
  • Labor: $80–$180
  • Estimated total: $100–$260

• Timing chain/belt related issues (timing chain, tensioner, guides)

  • Parts: $100–$400 (chains, tensioners, guides; belts if applicable)
  • Labor: 4–8 hours or more depending on access and engine variant
  • Estimated total: $600–$2,000+ (including possible water pump and gaskets)
  • Note: This is a high-cost repair with potential scope growth if other timing-related wear is found.

• VVT solenoid or oil passage repair

  • Parts: $60–$180
  • Labor: $100–$250
  • Estimated total: $160–$430

• Gaskets, seals, and fluids (oil, filter)

  • Parts: $20–$60
  • Labor: often included in above if additional repairs are performed
  • Estimated total: $40–$120

• Reprogramming or ECU updates (if required)

  • Parts: often none; software update
  • Labor: $50–$150 (dealer or specialized shop)

DIY vs PROFESSIONAL

• Cam sensor replacement (Bank 2) and basic wiring checks are within reach for a skilled DIYer with a basic set of tools, a DVOM or oscilloscope, and a good service manual. Key caveats:
  • Ensure you disconnect the battery before disconnecting electrical connectors.
  • Take care not to damage the sensor or wiring when disconnecting/connecting.
  • Relearn/idle procedures may be required after sensor replacement; follow OEM service procedures.
• Timing-chain-related work (Step 5) is significantly more complex and can risk severe engine damage if mis-timed. This is usually best left to a professional with timing tool access and engine timing experience.
• If you’re uncertain about diagnosing timing or ECU-related possibilities, start with the sensor and wiring, then consider a dealer or trained shop for deeper timing/VVT checks.

PREVENTION

• Regular, timely oil changes with the correct grade and specification for the FA engine (Subaru recommends the OEM spec; commonly 0W-20 synthetic for many models) to keep VVT and timing components well-lubricated.
• Monitor for oil leaks and fix promptly; oil contamination can degrade cam sensors and VVT components.
• Use quality air and oil filters; keep the engine clean from debris that can affect sensors and intake.
• Address check engine light promptly; intermittent signals can point to creeping wear or wiring issues before they cause major failure.
• If you notice symptoms such as stalling, misfires, or hard starting, perform a diagnostic check sooner rather than later to prevent potential further damage.

Data limitations and transparency

• The provided data states: No owner complaints found for this make/model/year/issue combination and No recalls found in the NHTSA database. This means there are no official complaint or recall references to cite for this exact scenario in the data you supplied. The diagnostic guidance above combines general cam sensor and Subaru engine knowledge with typical failure modes to help you approach P0346, but it should not be treated as a document of observed failures for this exact vehicle. If you have access to dealership Service Information (TIS/Service Bulletins) or updated NHTSA entries, those could provide model-year-specific guidance or notes.
• If you are working on a specific engine variant (e.g., FA20D vs. another FA family variant) or if there are any aftermarket modifications, adapt the steps accordingly.