P0024 on 2013-2019 Subaru Outback 2.5L: Exhaust Cam Timing Causes and Fixes

What's Unique About the 2013-2019 Subaru Outback

The FB25 engine's variable valve timing (AVCS) system is highly sensitive to engine oil level and cleanliness. Many P0024 codes on these vehicles are triggered simply by oil that is low, dirty, or of the incorrect viscosity. Unlike older Subaru EJ-series engines that had problematic filters in the banjo bolts for the AVCS system, the FB25 design integrated these into the cam carriers, making them less of a service item but reinforcing the need for clean oil. Owner experiences frequently show that an oil change, sometimes with an engine flush, can resolve the code without replacing any hardware. TSB 02-163-16R specifically directs technicians to check oil condition as a primary step for any AVCS-related code on this engine.

Generation note: This guide covers the 2013-2014 (4th Gen, BR) and 2015-2019 (5th Gen, BS) Subaru Outback. Both generations use the FB25 2.5L engine with a timing chain and Dual AVCS, and the causes and repair procedures for P0024 are consistent across this year range.

Symptoms You May Notice

• Check Engine Light is on
• Cruise control light may flash (a common Subaru behavior when the CEL is on)
• Traction control light may be on
• Rough or unstable idle
• Engine may hesitate or stumble on acceleration
• Reduced engine power
• Decreased fuel economy
• Engine may stall at stops
• Hard starting

Most Likely Causes

1. Low or Dirty Engine Oil 🔴 High Probability The AVCS system relies on clean oil at the correct pressure to function. Sludge or low levels can prevent the camshaft phasers from moving as commanded by the ECM. The FB25 engine, particularly early models, can also be prone to oil consumption, making low oil levels a frequent issue.
   How to confirm: Check the engine oil dipstick. The oil should be between the 'low' and 'full' marks and should not appear excessively dark, thick, or sludgy. If the level is low, top it off and see if the code clears after a drive cycle. If the oil is dirty, an oil change is the next step.
   Typical fix: Perform an engine oil and filter change using the manufacturer-specified oil (typically 0W-20 synthetic). Many owners and technicians recommend using an engine flush additive before the oil change to help clear out sludge from oil passages. 🎬 See: How to perform an engine flush to clear sludge
   Est. part cost: $40-$90
2. Faulty Bank 2 (Driver's Side) Exhaust Oil Control Valve (OCV) 🟡 Medium Probability → Shop Engine Variable Valve Timing (VVT) Solenoid The OCV is an electromechanical solenoid that can fail electrically or become clogged with debris from dirty oil, causing it to stick in one position. It is the most common hardware failure for this code.
   How to confirm: After verifying oil is clean and full, use a scan tool to monitor commanded vs. actual cam angle for Bank 2 Exhaust. A large discrepancy points to the OCV. You can also test the solenoid's resistance with a multimeter (should be 6.9-7.9 ohms). The definitive test is to swap it with the passenger side exhaust OCV (if they are the same part number). If the code follows and changes to P0014, the OCV is bad.
   Typical fix: Replace the Bank 2 (driver's side) exhaust OCV. This valve is located on the lower part of the engine, sometimes partially behind the timing cover. 🎬 Watch: Step-by-step Bank 2 exhaust OCV replacement guide
   Est. part cost: $70-$150
3. Clogged Oil Passages ⚪ Low Probability If oil changes have been neglected, sludge can build up and restrict the small passages leading to the OCV and camshaft phaser, even if the oil is subsequently changed. The AVCS system is particularly vulnerable to this.
   How to confirm: This is difficult to confirm without disassembly. An engine flush additive used before an oil change may help clear minor blockages. If a known-good OCV is installed and the problem persists, this becomes a more likely cause.
   Typical fix: Perform an engine flush. In severe cases, removal of the cam carrier or front timing cover may be needed for manual cleaning.
   Est. part cost: $15-$30 for engine flush additive.

Rare But Worth Checking

• Stretched Timing Chain or Failed Tensioner: → Shop Engine Timing Chain While the FB25 uses a 'lifetime' timing chain, it can stretch over very high mileage or due to poor maintenance, causing timing correlation codes. A Subaru technician on Reddit noted they have almost never seen an FA/FB engine jump time, making this a very rare cause. Diagnosis involves checking cam/crank correlation with the OCVs unplugged.
• Failed Camshaft Phaser (AVCS Actuator): → Shop Engine Camshaft The mechanical gear on the end of the camshaft can fail or become stuck, but this is less common than the OCV failing. This would typically be diagnosed after replacing the OCV with no success.

Diagnosis Steps

1. Check Engine Oil Level and Condition: This is the most important first step. If the oil is low, top it off. If it is dirty or past its service interval, perform a complete oil and filter change. Consider using an engine flush product during the oil change.
2. Scan for Codes: Confirm P0024 is the only code present. If other codes like P0014 are also present, it reinforces the likelihood of an oil quality/pressure issue.
3. Analyze Live Data: Use a scan tool that can read live data. Monitor the 'Commanded' vs. 'Actual' camshaft position for 'Bank 2 Exhaust'. At idle, they should be very close. If there is a significant, persistent difference (e.g., actual is stuck at 40 degrees while commanded is 0), it confirms a mechanical or hydraulic fault.
4. Inspect the Oil Control Valve (OCV): Locate the exhaust OCV on the driver's side of the engine, on the lower front area. Inspect the wiring and connector for damage. You can test the solenoid's internal resistance with a multimeter (should be 6.9-7.9 ohms) or briefly apply 12V to see if it clicks.
🎬 Watch: How to test and fix a P0024 code
5. Swap the OCVs (Diagnostic Test): The exhaust OCVs for Bank 1 and Bank 2 are typically the same part. Swap the driver's side and passenger's side solenoids. Clear the codes and drive the vehicle. If the code changes to P0014 (Bank 1), you have confirmed the OCV is faulty and needs to be replaced.
6. Inspect Mechanical Timing: If all the above steps fail to resolve the issue, the problem may be more serious, such as a stretched timing chain, a failed tensioner, or a faulty camshaft phaser. This level of diagnosis is best left to a professional.

Parts You'll Likely Need

• Engine Oil and Filter — Low or contaminated oil is the number one cause of this code. An oil change is the cheapest and easiest first step.
  Trusted brands: Idemitsu (OEM supplier), Mobil 1, Castrol, Pennzoil
  OEM price range: $60-$90
  Aftermarket price range: $40-$70
• Exhaust Oil Control Valve / VVT Solenoid (Bank 2) (OEM #10921AA231 (superseded by 10921AA23B for later models)) — This solenoid controls the oil flow for the AVCS system and is the most common component to fail if an oil change does not resolve the code. Part number 10921AA231 was used on earlier models and is superseded by 10921AA23A and then 10921AA23B on later models. Check with a dealer for the correct part for your specific VIN.
  Trusted brands: Subaru (Genuine), Denso (OEM)
  OEM price range: $100-$150
  Aftermarket price range: $70-$120

Related Codes That Often Appear With This One

• P0014 — This is the equivalent code for Bank 1 (passenger side) exhaust camshaft. If both P0014 and P0024 appear together, it strongly points to a systemic issue like very low/dirty oil or low oil pressure affecting both banks.

Technical Service Bulletins (TSBs) & Recalls

• TSB 02-163-16R: Provides detailed inspection and repair procedures for AVCS-related DTCs, including P0024, on FA/FB engines. It outlines a diagnostic flowchart that prioritizes checking oil condition before replacing parts and details how to check mechanical timing.
• TSB 02-132-12R: This bulletin provides specific diagnosis and repair instructions for AVCS-related DTCs including P0011, P0014, P0021, and P0024.
• TSB 11-193-20R: While not directly for P0024, this TSB for other models (Ascent) shows that sometimes an ECM logic update is released to fix erroneously set cam timing codes.

Mechanic-Grade Diagnostic Values

• Oil Control Valve (OCV) Solenoid Resistance — expected: 6.9 - 7.9 Ohms at 68°F (20°C). Failure: A reading outside this range, or an open/short circuit, indicates a failed solenoid.
• Live Data: Mechanical Cam/Crank Correlation — expected: Close to 0° at idle. Failure: A value of +/- 10° or more indicates the timing chain has likely jumped a tooth. The cam sprockets have 36 teeth, so one tooth equals 10 degrees of rotation.
• Live Data: Commanded vs. Actual Cam Angle — expected: Actual angle should match commanded angle within 5-10 degrees during operation.. Failure: A large, persistent deviation between the commanded and actual values points to a hydraulic or mechanical issue (stuck OCV or phaser).

Hidden / Shadow Codes Worth Checking

• Mode $06: AVCS Diagnostic Value: This is not a standard DTC, but a manufacturer-specific test value stored in Mode $06 data. It represents a diagnostic result for the AVCS system. A high value indicates a detected fault. (see via A professional scan tool like the Subaru Select Monitor (SSM) or another advanced scanner capable of reading Mode $06 data. According to TSB 02-163-16R, a value greater than or equal to 1000 is the threshold for a problem.)

Scan Tool Commands That Help

• Subaru Select Monitor (SSM) or equivalent: AVCS Diagnostic Procedure (Manual Test) — To isolate a mechanical timing issue (stretched/jumped chain) from a hydraulic/electrical one. The procedure involves unplugging the OCVs, starting the engine, and observing the cam position live data to see the base mechanical timing without hydraulic influence.
• Subaru Select Monitor (SSM) or equivalent: Clear Learned ECM Values / Memory Reset — After a major mechanical repair like a timing chain replacement. The ECM can retain old learned values and continue to set timing codes even if the mechanical fault is fixed. A special reset procedure may be required to clear this memory.

Wiring & Ground Locations

• OCV Solenoid Ground Strap — The Bank 2 (driver's side) exhaust OCV has a small ground strap attached to one of its 10mm mounting bolts.. A loose or corroded ground strap can cause intermittent electrical issues for the solenoid, leading to erratic operation and potentially triggering a P0024 code. Ensuring this ground is clean and tight is a critical part of replacing the OCV.

Real Owner Repair Stories

• Reddit user Upbeat_Confidence739 (2019 Subaru Crosstrek (Uses similar FB-series engine and AVCS logic)) — Check engine light with codes P0014 and P0024 present simultaneously.
  ❌ Tried (didn't work) Initial diagnosis pointed towards potential timing issues or failed OCVs.
  ✅ What actually fixed it The user performed an engine flush using an additive from an auto parts store, followed by a standard oil and filter change. This resolved both codes without replacing any parts.
• NHTSA ODI #11470699 (Subaru XV Crosstrek) — An owner reported that while the car was still running and drove fine with the accelerator pressed, the engine warning light illuminated and caused the cruise control to malfunction; the error code was later identified as P0024.

OEM Part Supersession History

• 10921AA220 → 10921AA230, then 10921AA231 — Progressive design updates by the manufacturer.
• 10921AA23A → 10921AA23B — Progressive design updates by the manufacturer.
  Heads up: While the solenoids may look physically similar, it is critical to use the correct part number for the vehicle's VIN. The 2015-2016 models fall in a transition period, making VIN verification essential.

Model Year Variations Within This Range

• 2013-2014 (4th Gen 'BR'): These earlier FB25 engines are more commonly associated with oil consumption issues, which can lead to low oil levels and trigger P0024. They typically use the earlier OCV part number, 10921AA231.
• Late 2016-2019 (5th Gen 'BS'): These models use an updated OCV, part number 10921AA23B, which superseded 10921AA23A. The changeover date was reportedly October 20, 2016. While the failure mode is the same, ordering the correct part number is crucial.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Excessive Oil Consumption 🔴 High — More common on early FB25 engines (approx. 2013-2014 models). Caused by piston ring design. A class-action lawsuit led to a warranty extension. (Ref: TSB 02-157-14R outlines the oil consumption test and short block replacement procedure for verified cases.)
• CVT Transmission Failure / Hesitation 🔴 High — Widespread issue on many models from 2010-2017, causing shuddering, hesitation, or stalling. (Ref: Subaru extended the CVT warranty to 10 years/100,000 miles for many affected vehicles, including 2013-2015 Outbacks.)
• Failing Wheel Bearings 🟠 Medium — A humming or grinding noise from the wheel area that increases with speed is a common complaint, often requiring replacement of the hub assembly.
• Windshield Wiper Motor Failure 🟡 Low — Wiper motor components could interfere with each other, causing the motor to overheat and fail. (Ref: Recall WTK-71 (supersedes 11V-469) was issued for 2010-2014 Outback models to replace the wiper motor bottom cover.)
• Infotainment Screen Delamination / Ghost Touch 🟠 Medium — Common on 2018-2019 models with the larger touchscreen, leading to phantom inputs or unresponsiveness. A class-action lawsuit was filed over this issue.
• Rapid Battery Drain 🟠 Medium — Some owners report batteries dying prematurely. A class-action lawsuit alleged a defect causes parasitic drain even when the car is off.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used OEM Oil Control Valve (OCV) from a reputable salvage yard can be a cost-effective choice, especially for diagnostic purposes (to confirm the original part is faulty by swapping). Given the high cost of new OEM solenoids, a used part can be a smart buy if the donor vehicle's history is known.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Ask for the VIN of the donor car to verify low mileage and the correct model year.
• Inspect the solenoid's mesh screen. It should be perfectly clean and free of any metallic debris or sludge.
• Avoid parts from engines that show signs of heavy sludge buildup under the oil filler cap.

OEM-only on this vehicle (don't cheap out):

• While not strictly 'OEM-only', using a Genuine Subaru or Denso (the OEM manufacturer) OCV is very strongly recommended. Cheap, unbranded aftermarket solenoids have a high failure rate and may not perform to the correct specifications, causing the code to return.

Aftermarket brands forum-validated for this vehicle:

• Denso

Brands owners have reported issues with on this vehicle:

• Unbranded, low-cost solenoids found on marketplaces like Amazon or eBay are generally not recommended by forum veterans.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0014 — The Bank 1 (passenger side) equivalent of P0024; often appears alongside P0024 when the issue is general oil quality or low oil pressure.
• P0011 — Intake-side camshaft timing over-advanced (Bank 1), sharing the same root causes of oil sludge or OCV failure within the AVCS system.
• P0021 — Intake-side camshaft timing over-advanced (Bank 2), which is the driver's side companion to the P0024 exhaust timing code.

Frequently Asked Questions