P0021 on 2013-2016 Scion FR-S: Causes and Fixes for Over-Advanced Cam Timing

What's Unique About the 2013-2016 Scion FR-S

The Scion FR-S is mechanically identical to the Subaru BRZ, so it uses Subaru's AVCS technology, which is highly dependent on oil pressure and cleanliness. A notable characteristic of Subaru engines is the use of small mesh filters in the oiling system to protect AVCS components; these can clog and cause timing issues. Additionally, 2013 models were subject to a valve spring recall (NHTSA 18V-772). Many owners reported subsequent engine issues, including P0021, widely attributed to technicians using excessive sealant during reassembly, which then broke off and clogged critical oil passages.

Symptoms You May Notice

• Check Engine Light is on
• Rough or unstable idle, sometimes described as 'hunting' RPMs
• Engine stalling, especially when coming to a stop or when the clutch is depressed.
• Noticeable decrease in engine power and acceleration
• Reduced fuel economy
• Rattling, knocking, or ticking noises from the engine, particularly the front timing cover area

Most Likely Causes

1. Low or Dirty Engine Oil 🔴 High Probability The AVCS system is hydraulic and extremely sensitive to oil level, pressure, and viscosity. Extended oil change intervals can lead to sludge that impedes the system's function. This is the first and most important check.
   How to confirm: Check the oil level on the dipstick. Inspect the oil's color and consistency. If it is low, dark black, or sludgy, it needs to be changed immediately.
   Typical fix: Change the engine oil and filter using a high-quality 0W-20 synthetic oil that meets manufacturer specifications. Reset the code and drive the vehicle to see if the code returns.
   Est. part cost: $40-$80
2. Faulty Oil Control Valve (OCV) / VVT Solenoid (Bank 2) 🔴 High Probability → Shop Engine Variable Valve Timing (VVT) Solenoid The OCV is an electronic solenoid that can fail electrically or become mechanically stuck due to sludge or debris from the engine oil, preventing it from correctly regulating oil flow to the cam phaser. This is the most common part to fail after oil issues are ruled out.
   How to confirm: Swap the Bank 2 (driver's side) intake OCV with the Bank 1 (passenger's side) intake OCV. They are identical parts, located on the top front of the engine, each held by a single 10mm bolt. Label the electrical connectors before swapping. Clear the codes and drive. If the trouble code changes to P0011 (Bank 1), the OCV is confirmed to be faulty.
   Typical fix: Replace the faulty Oil Control Valve. It is recommended to replace the O-ring as well. The OEM part number is SU003-07806, which replaces the older SU003-00096.
   Est. part cost: $80-$130
3. Clogged AVCS Oil Passage or Filter Screen 🟡 Medium Probability The FA20 engine has small, thimble-shaped filter screens located in the cylinder heads before the AVCS solenoids. These can become clogged with sludge or debris, especially if oil changes are neglected or if sealant was used improperly during a previous repair (like the valve spring recall).
   How to confirm: This is difficult to confirm without disassembly. If an oil change and a new OCV do not fix the code, this is the next logical suspicion. Accessing these filters requires removing the cam carriers, which is a significant job.
   Typical fix: Requires removing components to access and clean or remove the filter screens and flush the oil passages. Many owners on forums elect to remove these filters entirely during an engine rebuild to prevent future clogging, accepting the risk of debris reaching the solenoid. This is often best left to a professional.
   Est. part cost: $5-$20 for gaskets, plus significant labor

Rare But Worth Checking

• Failing Intake Camshaft Sprocket (Bank 2): → Shop Engine Camshaft The mechanical sprocket (phaser) itself can fail internally or get stuck in the advanced position. This is a more complex and expensive repair that involves removing the timing cover. A user on ft86club.com detailed a dealer replacing the cam sprocket to fix a persistent P0021.
• Stretched Timing Chain or Failed Tensioner: → Shop Engine Timing Chain While not common, a stretched chain or failing tensioner can cause the base timing to be off, leading the AVCS system to operate outside its expected range and trigger a fault. This usually presents with correlation codes (P0016, P0018) as well.
• ECU Logic or Learning Issues: In some rare cases, particularly after a battery disconnect, clutch replacement, or other major work, the ECU can get 'stuck' with incorrect learned values for the VVT system, repeatedly throwing codes even when mechanical components are sound. This can sometimes be resolved by a reflash or, in extreme cases, ECU replacement.

Diagnosis Steps

1. Check Engine Oil: Verify the oil level is full and the oil is clean. If low or dirty, perform an oil and filter change with 0W-20 synthetic oil. Clear the code and test drive. This is the most critical first step.
2. Scan for Codes: Use an OBD-II scanner to confirm P0021 is the only code. If other codes are present (especially P0011, P000C, P0018), their combination can help pinpoint the issue.
3. Swap the Oil Control Valves (OCVs): The intake OCVs for Bank 1 and Bank 2 are identical and easily accessible on top of the engine. Label the connectors, swap the solenoids (one 10mm bolt each), clear the codes, and drive the vehicle.
4. Re-scan for Codes: If the code returns as P0011, the OCV you moved to Bank 1 is faulty and needs replacement. If P0021 returns, the original OCV is likely good, and the problem lies elsewhere.
5. Inspect OCV Port: If the OCV is not the issue, remove the Bank 2 OCV again and inspect the port for sludge or debris that could indicate a clogged passage. A user on ft86club.com noted that sealant from a previous repair clogged their passages.
6. Professional Diagnosis: If the above steps do not resolve the issue, the problem is likely a clogged internal oil passage/filter, a failing cam sprocket, or a timing chain issue, which requires professional diagnosis and repair.

Parts You'll Likely Need

• Cam Timing Oil Control Valve (OCV) (OEM #SU003-07806) — This solenoid is the most common part to fail for this code, either by sticking mechanically or failing electrically. It directly controls oil flow for cam phasing. The part number SU003-07806 replaces the previous number SU003-00096.
  Trusted brands: Toyota/Subaru Genuine, Dorman, NTK
  OEM price range: $80-$130
  Aftermarket price range: $50-$90
• Engine Oil and Filter — The AVCS system is highly sensitive to oil quality and level. An oil change is the simplest and cheapest first step in diagnosis and is often the solution.
  Trusted brands: Mobil 1 0W-20, Pennzoil Platinum 0W-20, Castrol Edge 0W-20
  OEM price range: $60-$100 (for filter and oil)
  Aftermarket price range: $40-$80

Related Codes That Often Appear With This One

• P0011 — This is the equivalent code for Bank 1 (passenger side). If both appear together, it strongly suggests a systemic problem like very low/dirty oil, low oil pressure from a failing pump, or a base timing issue with the timing chain.
• P000C — This code indicates a slow response from the Bank 2 intake camshaft position. It often appears with P0021 and points directly to a sluggish or stuck OCV or a clogged oil passage.
• P0018 / P0019 — These are crankshaft-camshaft correlation codes for Bank 2. If they appear alongside P0021, it can indicate a more serious mechanical timing issue, such as a jumped tooth on the timing chain or a problem with the reluctor wheel.

Technical Service Bulletins (TSBs) & Recalls

• Subaru TSB 02-163-16R: Provides updated diagnostic procedures for AVCS-related DTCs, including P0021, for FA and FB engines. It emphasizes checking oil condition first, then OCVs, then oil pressure, and finally internal components. It covers the entire family of AVCS codes (P000A-D, P0011-P0024, P0016-P0019).

Platform-Specific Known Issues

• A recall for the engine valve springs on 2013 models (NHTSA 18V-772) involved a complex, 12-hour repair where the engine was removed. Many owners reported engine issues post-recall, with widespread speculation and evidence on forums like ft86club.com suggesting that improper application of sealant by technicians led to clogged oil pickup tubes and passages, starving the engine of oil and triggering codes like P0021.

Mechanic-Grade Diagnostic Values

• Oil Control Valve (OCV) Resistance — expected: 6.9 to 7.9 Ohms at 68°F (20°C). Failure: A reading outside this range, or an open/infinite reading, indicates a faulty solenoid coil.
• AVCS Learned Value (via Techstream/SSM) — expected: Intake: Min 52, Max 72. Exhaust: Min 78, Max 98.. Failure: A value outside of these ranges (e.g., an intake value of 46) points to a mechanical issue with the cam sprocket or its installation, preventing it from reaching its full range of motion.
• AVCS Diagnostic Value (Mode $06) — expected: Value should be >= 1000 after a drive cycle.. Failure: A value of 0 indicates the diagnostic has not completed. A value less than 1000 after the diagnostic runs suggests a fault in the system.
• VVT Advance Angle Amount at Idle (via Techstream/SSM) — expected: 0 degrees within 10 seconds of starting the engine (with OCV unplugged).. Failure: A value more than +/- 10 degrees indicates a base timing issue, such as a slipped timing chain tooth (as each tooth represents approximately 10 degrees).

Scan Tool Commands That Help

• Toyota Techstream or Subaru Select Monitor (SSM): Read 'AVCS diagnostic value' (Mode $06) — Use after a repair attempt (like an OCV replacement) and a specific drive cycle to confirm if the fault is truly gone. A value of >= 1000 indicates a pass.
• Toyota Techstream or Subaru Select Monitor (SSM): Read 'VVT Initial Learning Positions' — To check the stored calibration values for the cam phasers. If these values are out of spec, it can indicate a mechanical problem or a 'stuck' ECU memory that may require a reset.
• Toyota Techstream or Subaru Select Monitor (SSM): VVT Active Test — This bidirectional control allows a technician to command the OCV duty cycle and observe the change in camshaft angle in real-time, confirming if the OCV and cam phaser are responding to commands.
• EcuFlash or other tuning software: Flash a different year's stock ROM, then flash back to the original. — This is an advanced, unofficial method reported by forum users to force a reset of the non-volatile 'Initial Position Learning Values' when the ECU refuses to relearn after a repair, as a last resort before replacing the ECU.

Real Owner Repair Stories

• ft86club.com user 'SamCon7' (2015 Scion FR-S) — Car would not idle for more than 2 minutes and would shut off when RPMs dropped below 1k. Codes P0011, P0016, P0018, and P0021 all appeared at once.
  ❌ Tried (didn't work) Initial diagnosis from a dealer suggested replacing Oil Control Valves and checking the timing chain.
  ✅ What actually fixed it The issue occurred immediately after a clutch replacement. The root cause was identified by other forum members as a likely damaged or improperly installed crankshaft reluctor wheel, which is located behind the flywheel and provides the primary signal for crank position.
• ft86club.com user 'BlueLine' (Scion FR-S (year not specified)) — Persistent P0011 and P0021 codes, rough idle.
  ❌ Tried (didn't work) Replaced all 4 cam position sensors, swapped OCVs, physically verified timing marks multiple times, replaced both intake cam sprockets with updated parts, performed ECU reset via battery disconnect.
  ✅ What actually fixed it After extensive and costly parts replacement, the final fix was a new crankshaft position sensor. The user noted the issue began after a clutch replacement and extended period with the battery disconnected.
• Reddit user 'ZealousidealJaguar98' (2013 Scion FR-S) — P0019 and P0021 codes, high initial idle, slow acceleration.
  ❌ Tried (didn't work) Swapped intake camshaft position sensors, swapped intake OCVs, confirmed oil was fresh.
  ✅ What actually fixed it The user performed a manual test by turning the crankshaft by hand and observed the Bank 2 intake cam sprocket would 'snap' into place rather than move smoothly, indicating a mechanical failure within the phaser. The final fix was replacing the intake camshaft sprocket (phaser).

OEM Part Supersession History

• SU003-00096 → SU003-07806 — Updated design/revision for the Oil Control Valve (OCV).
• Unknown → 10921AA231 — This is another part number associated with the FA20 OCV, potentially a direct Subaru part number versus the Toyota/Scion number. It is listed as compatible.

Model Year Variations Within This Range

• 2013 Only: Subject to a valve spring recall. Oiling holes in rocker arm pivots were different sizes on driver vs. passenger side heads.
• 2014+: Received updated rocker arms and pivots with deeper pockets, possibly to prevent rockers from being kicked out. Oiling holes in pivots were made a uniform size.
• 2015+: Received an upgraded engine sub-harness and improved ignition coil packs.
• 2016: No significant powertrain changes from 2015. A backup camera became standard.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Premature Throw-Out Bearing (TOB) Failure 🟠 Medium — Common on 2013-2016 manual transmission models, often failing between 60,000-80,000 miles. Symptoms include a grinding or chirping noise when the clutch pedal is depressed.
• Valve Spring Fracture (2013 Models) 🔴 High — Specific to a range of 2013 models, leading to potential engine stall. A recall (NHTSA 18V-772) was issued. (Ref: NHTSA Campaign ID: 18V772000)
• Engine Failure Post-Valve Spring Recall 🔴 High — A significant number of owners reported engine failures shortly after the valve spring recall was performed, widely believed to be caused by excessive sealant application by technicians, which clogged oil passages. (Ref: NHTSA Campaign ID: 18V772000 (related))
• High-Pressure Fuel Pump 'Crickets' 🟡 Low — A common, often benign chirping noise from the engine bay at idle, caused by the high-pressure fuel pump. While annoying, it is not typically indicative of imminent failure.
• Tail Light Condensation/Leaking 🟡 Low — Common across all years. The foam gaskets for the tail light assemblies degrade, allowing water to enter the trunk and the light housings themselves.
• Ignition Key Interlock Failure 🟠 Medium — Affected 2013-2016 models, allowing the key to be removed when the automatic transmission is not in Park. (Ref: Toyota Recall JLE / NHTSA 16V-092)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this code, a used Oil Control Valve (OCV) can be a cost-effective diagnostic step, especially if pulled from a known-good, running vehicle. If swapping a used OCV resolves the code, it's still recommended to purchase a new OEM part for long-term reliability. Structural engine components like the timing cover or cam carriers are also good candidates for used parts if damaged during a repair.

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

What to inspect on the donor part:

• For an OCV, ensure the screen is intact and free of metal shavings.
• Check for signs of heavy sludge or varnish on the part.
• Ask for the donor vehicle's VIN to check for accident history or flood damage.
• If possible, test the resistance of a used OCV with a multimeter before purchasing; it should be between 6.9-7.9 ohms.

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

• Camshaft Sprocket (Phaser): Aftermarket versions are not widely available or trusted. Given the complexity of the job, using a new OEM sprocket is critical to avoid repeat failures.
• Timing Chain and Tensioners: This is a labor-intensive job where using high-quality OEM parts is essential for engine longevity.
• Engine Control Unit (ECU): Due to programming and VIN-locking, a used ECU is often more trouble than it's worth unless you have access to specialized tools and knowledge.

Aftermarket brands forum-validated for this vehicle:

• NTK (for sensors and some solenoids)
• Dorman (often offers redesigned or improved versions of OEM parts, but quality can vary)

Brands owners have reported issues with on this vehicle:

• Unnamed, no-brand 'white box' solenoids and sensors from online marketplaces. These frequently fail out of the box or have incorrect electrical specifications, causing more diagnostic headaches.

Real Owner Stories

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

Related OBD-II Codes

• P0011 — The Bank 1 equivalent of P0021; often used for diagnostic swapping to confirm if an Oil Control Valve is faulty.
• P000C — Indicates slow response in the Bank 2 cam position; often appears alongside P0021 when oil passages are restricted.
• P0018 — Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A); frequently appears with P0021 when timing is physically affected or sensors are misaligned.
• P0016 — The Bank 1 companion to P0018; part of the family of AVCS/timing codes covered under TSB 02-163-16R.
• P000A — Intake Camshaft Position Slow Response (Bank 1); listed in TSB 02-163-16R as a related AVCS diagnostic code.

Frequently Asked Questions