P0021 on Subaru: How to Diagnose & Fix
Intake Camshaft Position Timing - Over-Advanced (Bank 2)
5 Subaru models · 6 documented issues · 2 critical · $50-$3,500 repair
P0021 on Subaru by model: symptoms, diagnosis and fix
The FA20 engine in the BRZ consumes oil at elevated rates during high-RPM driving, spirited canyon runs, and track use. The engine design with direct injection and high compression (12.5:1) combined with the oil-fed variable valve timing system means oil consumption increases significantly when the engine is frequently operated above 5,000 RPM. Consumption rates of 1 quart per 1,000-2,000 miles are reported by owners who drive aggressively. The narrow oil galleries in the FA20 make proper oil level maintenance critical.
Common Symptoms
- Oil level drops noticeably after spirited driving or track days
- Low oil pressure warning during hard cornering (oil starvation)
- Oil consumption of 1 qt per 1,000-2,000 miles with aggressive driving
- Blue smoke under hard acceleration
- Oil level normal during city/highway commuting but drops during performance driving
How to Fix
Check oil level before and after every spirited drive or track day. Carry an extra quart of 0W-20 (OEM spec) or 5W-30 (commonly used upgrade for track use). For track cars, install an oil catch can (Radium Engineering 20-0255-02 or Crawford Performance V3) to reduce oil vapor entering the intake. Consider an oil cooler for track use. Subaru considers up to 1 qt per 3,000 miles as acceptable.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru SOA427V1310 synthetic 0W-20 engine oil, 1 quart
2013-2020 Subaru BRZ FA20 according to the live product listing; for 2021 or any modified/track-use engine, confirm the current owner manual and oil specification before purchase.
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Sources for this issue (1)
The FB25's hydraulic timing-chain tensioners can bleed down overnight, so on a cold start the chain is momentarily slack and slaps the chain cover/guides, producing a metallic rattle for the first few seconds until oil pressure builds. A brief rattle is common; a rattle that persists 3-4 seconds or grows over time indicates worn tensioners and guides and risks chain skip if ignored. Owners report dealers replacing both tensioners, both chains and all guides on higher-mileage cars.
Common Symptoms
- Metallic rattle/clatter for a few seconds at cold start
- Rattle that lengthens or worsens over time
- Rattle returns after the car sits overnight
- Occasional rough running if chain has stretched
- Noise reduced after an oil change
How to Fix
Use the correct-grade oil (0W-20) and keep oil fresh; many owners find a brief startup rattle is normal. If the rattle lasts more than ~3 seconds or worsens, have the timing chain tensioners, chains and guides inspected and replaced as a set before a guide breaks or the chain jumps time. Confirm oil pressure and check for sludge that can starve the tensioners.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru 13142AA103 Timing Chain Tensioner
one component of the diagnosed timing repair, not a universal kit or proof of failure Fitment/availability: One tensioner position for retailer-cataloged 2011-2016 Forester 2.5L FB25 applications; confirm VIN, production date, diagram po…
- Genuine Subaru 13143AA110 Timing Chain
cam-drive chain component only when inspection establishes chain/guide/tensioner replacement Fitment/availability: Retailer-cataloged 2014-2018 Forester FB25 branch in this issue; page states quantity two, but confirm VIN, production dat…
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Sources for this issue (2)
The turbocharger oil-feed line on the EJ255 uses a banjo (union) bolt containing a fine mesh screen meant to keep debris out of the turbo. As the engine ages or oil-change intervals stretch, sludge and carbon clog the screen and starve the turbo of oil. The turbo bearing then overheats and fails — the shaft can break and the compressor wheel disintegrate, sending metal debris into the oil pan, oil cooler and engine bearings, often destroying the engine. Subaru later deleted the screen on the union bolt because of these clogging-induced failures.
Common Symptoms
- Loud whine, whistle or grinding from the turbo
- Blue smoke from the exhaust
- Sudden loss of boost/power
- Knocking or low oil pressure
- Metallic debris found in the oil pan or screen
How to Fix
On EJ255 turbo Foresters, proactively remove and clean (or delete, per later Subaru practice) the banjo-bolt oil-supply screen at the turbo oil-feed line and keep to short synthetic-oil intervals. At the first sign of turbo whine, blue smoke, or low oil pressure, inspect the screen and oil-feed line before further driving. A failed turbo requires turbo replacement plus a thorough oil-system flush; if debris reached the bearings, engine teardown may be needed.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru 14445AA090 Turbo Oil-Supply Union Bolt with Screen
correct screened union bolt when inspection finds an obstructed or damaged screen Fitment/availability: 2009-2013 Forester XT EJ255 turbo branch explicitly listed; confirm VIN and feed location Fitment/availability: in stock with Add to …
- Genuine Subaru 803910050 Small Turbo Oil-Feed Copper Washer Pair
new sealing washers required when the screened union bolt is serviced Fitment/availability: 2009-2013 Forester XT explicitly listed; two washers supplied, confirm the serviced banjo connection Fitment/availability: in stock with Add to C…
- Genuine Subaru 15192AA590 Turbocharger Oil Pipe
replacement feed pipe only when restricted, damaged or not cleanable Fitment/availability: 2009-2013 Forester 2.5-liter turbo XT catalog branch; confirm VIN Fitment/availability: ships in 1-3 business days with Add to Cart live when revi…
- Genuine Subaru 14411AA710 Turbocharger Assembly
replacement only after turbo failure and its lubrication cause are confirmed Fitment/availability: 2009-2013 Forester XT turbo branch; confirm VIN and current supersession Fitment/availability: ships in 1-3 business days with Add to Cart…
- Tokyo Roki 15208AA100 Black Oil Filter
engine oil filter used with the correct oil service after contamination inspection Fitment/availability: Retailer specifies all turbocharged EJ engines, including the 2009-2013 Forester XT EJ255 branch Fitment/availability: in stock with…
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Sources for this issue (3)
The Active Valve Control System (AVCS) solenoids on the EJ257 engine are prone to failure from oil contamination and carbon buildup. When they stick or fail, the ECU cannot properly adjust camshaft timing, causing rough idle, hesitation, and reduced power. The solenoids are oil-controlled and degrade faster with extended oil change intervals or contaminated oil.
Common Symptoms
- Check engine light with AVCS-related codes
- Rough or hunting idle
- Hesitation on acceleration
- Reduced power in mid-range RPMs
- Occasional stalling at idle
How to Fix
Replace the failed AVCS solenoid(s) — there are two on the EJ257, one per bank ($80-$150 each for parts). Clean the oil passages feeding the solenoids during replacement. Use OEM Subaru solenoids for reliability. Prevent future failures by using quality synthetic oil and changing every 3,000-4,000 miles under hard driving conditions. Some owners clean solenoids with brake cleaner as a temporary fix.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru 10921AA020 Intake AVCS Oil Control Valve
early intake OCV only after that valve fails electrical/hydraulic response testing Fitment/availability: EJ257 model years 2004-2006 intake AVCS position; sold individually, confirm VIN and bank Fitment/availability: In stock and ready t…
- Genuine Subaru 10921AA080 Intake AVCS Oil Control Valve
middle intake OCV branch only after that valve fails electrical/hydraulic response testing Fitment/availability: EJ257 model years 2006-2010 intake AVCS position; overlap years require VIN confirmation, sold individually Fitment/availabi…
- Genuine Subaru 10921AA140 Intake AVCS Oil Control Valve
late intake OCV branch only after that valve fails electrical/hydraulic response testing Fitment/availability: EJ257 model years 2010-2021 intake AVCS position; overlap years require VIN confirmation, sold individually Fitment/availabili…
- Genuine Subaru 10917AA060 Right Exhaust AVCS Oil Control Valve and Holder
right exhaust valve/holder assembly only after right exhaust response or contamination failure is proven Fitment/availability: EJ257 model years 2008-2021 right-hand exhaust AVCS position only; confirm VIN Fitment/availability: In stock …
- Genuine Subaru 10917AA070 Left Exhaust AVCS Oil Control Valve and Holder
left exhaust valve/holder assembly only after left exhaust response or contamination failure is proven Fitment/availability: EJ257 model years 2008-2021 left-hand exhaust AVCS position only; confirm VIN Fitment/availability: In stock and…
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Owner tips & cautions
- TipClean your AVCS solenoids every 30,000 miles as preventive maintenance. Remove them, spray with brake cleaner, and reinstall. Takes 20 minutes per side.
- TipShort oil change intervals (3,000-4,000 miles) with quality synthetic oil are the best prevention. The EJ257 is hard on oil and dirty oil kills AVCS solenoids.
On the EJ255-powered WRX (2006-2014), the turbocharger oil-supply banjo (union) bolt and the AVCS oil-supply banjo bolts contain small mesh filter screens. Over time the screens load up with sludge and debris, restricting oil flow to the turbo center section (and to the AVCS cam-phasing solenoids). The result is a turbo that runs its bearings dry — shaft play, oil smoke, then a failed CHRA that can dump metal into the intake and oil system — often preceded by cam-timing correlation codes. It is one of the most heavily documented failure chains on this engine and Subaru addressed it in a service bulletin (TSB 02-103-07) recommending the screens be serviced or removed.
Common Symptoms
- Turbo whine or shaft play
- Blue/white smoke from exhaust
- Loss of boost and power
- Check engine light with camshaft timing codes
- Low oil pressure to turbo
- Metal in oil
How to Fix
Inspect and clean or, per common shop practice and the Subaru bulletin, permanently remove the banjo-bolt filter screens (turbo feed and both AVCS feeds) and rely on the main oil filter. If the turbo already shows shaft play or smoke, replace the turbo, flush the oil feed and return lines, and fix the screen root cause at the same time. Use frequent oil changes with correct oil. No recall remedy exists; this is a maintenance/preventive item.
Sources for this issue (4)
P0011 sets when the Bank 1 (passenger-side) intake camshaft is advanced beyond the ECM's commanded position — the AVCS phaser is stuck advanced or the ECM can't control it. On the Outback this is almost always oil-related: low or dirty engine oil, or the passenger-side intake oil control valve (OCV) sticking, or the classic Subaru issue of clogged filter screens inside the banjo bolts that supply oil to the AVCS solenoids. The ECM drives the oil-flow control solenoids mounted on the valve covers, which move spool valves to route oil pressure into the cam phaser; any restriction over-advances or locks the cam. It often appears in extreme cold (thick cold oil starves the AVCS) and on cars with stretched oil-change intervals. A useful test is swapping the Bank 1 and Bank 2 intake OCVs and seeing whether the code follows to P0021.
Common Symptoms
- Check engine light
- Rough or unstable idle
- Hesitation or slight loss of power
- Worse in very cold weather
- Minor fuel-economy drop
How to Fix
Check oil level and condition first and change with spec 0W-20 synthetic if degraded. If the code persists, remove and clean/replace the AVCS banjo-bolt filter screens and replace the Bank 1 intake oil control valve (OCV, ~$95-350 OEM) — a straightforward job. Inspect the OCV connector/harness for open or short. Reset ECM VVT learned values after repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Subaru 10921AA231 Oil Control Valve
OCV only after the Subaru diagnostic path proves the valve fault Fitment/availability: 2013-2017 Outback 2.5-liter FB25 branch; confirm VIN and bank/position Fitment/availability: Add to Cart live when reviewed
- Genuine Subaru 10921AA23B Oil Control Valve
later OCV only after the fault is proven Fitment/availability: 2018-2019 Outback 2.5-liter FB25 branch within this card; current replacement for 10921AA23A, confirm VIN and position Fitment/availability: ships in 1-3 business days with A…
- Genuine Subaru 14451AA050 Cam-Carrier Oil Filter
filter only when the applicable TSB diagnostic procedure identifies restriction Fitment/availability: cataloged for the FB25 Outback branch; quantity and position are procedure/VIN dependent Fitment/availability: ships in 1-3 business da…
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Sources for this issue (3)
P0021 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0021 mean on a Subaru?
P0021 stands for "Intake Camshaft Position Timing - Over-Advanced (Bank 2)." P0021 means the engine computer detected that the intake camshaft on bank 2 is timed too far advanced and won't return to its commanded position. Most modern engines use variable valve timing (VVT), where an oil-pressure-driven actuator rotates the camshaft to optimize power and efficiency; the PCM compares the camshaft's actual position to its target. When the cam stays over-advanced beyond an acceptable limit, this code sets. Bank 2 refers to the side of the engine that does not contain cylinder number one. You may notice rough idle, reduced performance, or lower fuel economy. On Subaru it is documented across 5 models: BRZ, Forester, WRX STI, WRX, Outback.
What are the most common causes of P0021?
The most common causes of P0021 are: Dirty or low engine oil restricting the VVT system, Stuck or failed camshaft oil control valve (VVT solenoid) on bank 2, Clogged VVT solenoid screen or oil passage, Faulty camshaft position actuator / phaser, Wiring or connector fault at the VVT solenoid, Camshaft or crankshaft position sensor problems, Worn timing chain, guides, or stretched chain altering cam timing. The specific cause varies by vehicle.
How much does it cost to fix P0021 on a Subaru?
Published repair estimates on Subaru range from $50 to $3,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0021 on a different make?
View P0021 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.