P0333 on 2012-2016 Subaru Impreza: Knock Sensor Circuit High Causes & Fixes

What's Unique About the 2012-2016 Subaru IMPREZA

The 2012-2016 Impreza, with its naturally aspirated (NA) FB20B 2.0L engine, has a well-documented issue with this code. Subaru acknowledged in Technical Service Bulletin (TSB) #07-133-18R that the original knock sensor was not durable enough and prone to failure from heat, causing the plastic housing to crack. The official fix involves replacing the original sensor with a more robust version (P/N 22060AA180) that was initially designed for Subaru's Direct Injection Turbo (DIT) engines, improving heat resistance and longevity.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Reduced engine power and acceleration
• Worse than normal fuel economy
• Audible engine pinging or knocking (in rare cases)
• Hesitation during acceleration
• Hard starting (less common)

Most Likely Causes

1. Faulty Bank 2 Knock Sensor 🔴 High Probability → Shop Ignition Knock (Detonation) Sensor Subaru issued TSB #07-133-18R acknowledging the original sensor (P/N 22060AA160) lacked durability and was prone to cracking and internal failure from engine heat and vibration. The plastic housing becomes brittle and cracks, allowing moisture to enter and corrode the internal components.
   How to confirm: Visually inspect the sensor for cracks in the plastic casing, which is a very common failure sign. After visually inspecting the wiring, the most practical test is to replace the sensor 🎬 See how to diagnose and swap out a faulty sensor. with the updated part. If the sensor is accessible, you could swap it with the Bank 1 sensor and see if the code changes to P0328. A resistance test can be performed; a good sensor should read between 400 kΩ and 700 kΩ.
   Typical fix: Replace the failed Bank 2 knock sensor with the updated OEM part (P/N 22060AA180 for Japan-built or 22060AA18A for US-built vehicles). It is critical to torque the new sensor's mounting bolt to 17.7 ft-lbs (24 Nm) without using anti-seize compound.
   Est. part cost: $50-$100
2. Wiring or Connector Issue 🟡 Medium Probability The sensor is located on the engine block and is subject to heat and vibration, which can make wiring brittle or cause the connector to become loose or corroded over time. Rodent damage is also a known possibility in this area.
   How to confirm: Visually inspect the wiring harness leading to the knock sensor for any signs of damage, melting, chafing, or corrosion at the connector. Check for a solid connection at both the sensor and the ECM. Look for evidence of chewing if rodent damage is suspected. Check for a 5V reference signal at the harness connector with the key on, engine off; absence of voltage points to a wiring or ECM issue.
   Typical fix: Repair or replace the damaged section of the wiring harness or clean/replace the connector. In some cases, replacing just the pigtail connector is sufficient.
   Est. part cost: $10-$50
3. Engine Control Module (ECM) Fault ⚪ Low Probability → Shop Engine Control Module (ECM)
   How to confirm: This is a last resort after the sensor and wiring have been confirmed to be good. Requires advanced diagnostics by a professional technician, including checking for the 5V reference signal at the sensor connector. If voltage remains high at the ECM pin with the sensor disconnected, the ECM may be faulty.
   Typical fix: The ECM may need to be reprogrammed or replaced.
   Est. part cost: $500-$1000+

Rare But Worth Checking

• Rodent Damage to Wiring:

Diagnosis Steps

1. Read the trouble code with an OBD-II scanner to confirm P0333 is present.
2. Inspect the wiring and connector for the Bank 2 (driver's side) knock sensor. It is located on the back of the engine block, under the intake manifold runners. Look for any obvious signs of damage, melting, rodent chewing, or corrosion.
3. Inspect the sensor itself for visible cracks in the plastic housing, a tell-tale sign of failure on these models.
4. Ensure the connector is securely plugged in.
5. If wiring and connections appear good, test the sensor's internal resistance using a multimeter. Disconnect the sensor and measure between the pins. A reading between 400 kΩ and 700 kΩ is expected. An open circuit (infinite resistance) or a short (near zero ohms) indicates a bad sensor.
6. If the sensor tests good, check for a 5V reference signal at the harness-side connector with the key on, engine off.
7. If the wiring appears intact and reference voltage is present, the most likely cause is a failed sensor due to the known TSB issue.
8. Replace the knock sensor. This can be done from the top of the engine after removing the air intake ducting. A long (approx. 1-foot) socket extension and a 12mm socket are required to reach the bolt.
🎬 Watch: Step-by-step guide to replacing the Impreza knock sensor.
9. Torque the new sensor's bolt to exactly 17.7 ft-lbs (24 Nm). Do not use anti-seize compound. The sensor's orientation is also important; the connector should be at a 90-degree angle 🎬 Watch this DIY walkthrough for a successful sensor installation. to the front of the engine.
10. Clear the trouble code and test drive the vehicle to ensure the code does not return. Note that some scanners may show the code as 'permanent' until the car's computer completes a full drive cycle and verifies the fix.

Parts You'll Likely Need

• Knock Sensor (OEM #22060AA180) — This is the updated, more durable part recommended by Subaru in TSB #07-133-18R to fix the common failure of the original sensor (P/N 22060AA160). The TSB also lists P/N 22060AA18A for US-built models.
  Trusted brands: Subaru (Genuine), Denso (Often the OEM supplier), Hitachi, Standard Motor Products
  OEM price range: $50-$100
  Aftermarket price range: $30-$70

Related Codes That Often Appear With This One

• P0332 — P0332 is 'Knock Sensor 2 Circuit Low Input'. Both codes relate to the same sensor circuit and are mentioned in the same TSB. Seeing either code points strongly to a faulty sensor or wiring.

Technical Service Bulletins (TSBs) & Recalls

• 07-133-18R: Announces a design change for the knock sensor to improve durability and address DTCs P0327, P0328, P0332, and P0333. Specifies using the more robust DIT engine sensor (P/N 22060AA180 or 22060AA18A) on NA engines.

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB #07-133-18R) was issued by Subaru for a range of vehicles, including the Impreza. It acknowledges that the original knock sensors on naturally aspirated engines were prone to failure, setting codes like P0333. The bulletin specifies using a more durable sensor, originally for turbo engines, as the official replacement part to improve heat resistance.

Mechanic-Grade Diagnostic Values

• Knock Sensor Internal Resistance — expected: 530 kΩ to 580 kΩ. Some service manuals state a broader range of 400 kΩ to 700 kΩ.. Failure: A reading of 0 ohms (short), infinity/OL (open circuit), or a value significantly outside the specified range indicates a faulty sensor.
• Knock Sensor Harness Voltage (Key On, Engine Off) — expected: ~5 Volts DC between the signal wire and ground.. Failure: A reading of 0V suggests an open wire or ECM fault. A reading significantly above 5V could indicate a short to voltage.
• Knock Sensor AC Voltage Output (Dynamic Test) — expected: A small AC voltage reading (>1V AC) should be generated when tapping the engine block near the sensor with the engine running.. Failure: No AC voltage or a very low millivolt reading when tapping indicates the sensor's internal piezoelectric element has failed.

Wiring & Ground Locations

• E14 / R69 — The knock sensor connector itself, located on the driver's side (Bank 2) rear of the engine block.. This connector and its pigtail are common failure points due to heat and vibration, which can cause corrosion or wire fatigue leading to a P0333 code.
• GE-1 / GE-2 — Main engine ground points, typically located on the top center of the engine, often on the intake manifold.. A poor main engine ground can cause floating voltages and incorrect readings from various sensors, including the knock sensor. While not a direct cause, it should be checked if multiple electrical faults are present.
• Shielded Ground (B83) — The shield for the knock sensor wire is typically grounded at a joint connector near the ECU, not at the sensor itself.. The shield protects the low-voltage signal from radio frequency interference (RFI). A break in the shield or its ground connection could potentially allow stray voltage to be induced in the signal wire, possibly contributing to a 'Circuit High' fault.

Real Owner Repair Stories

• IH8MUD.com Forum User (2006 Toyota Land Cruiser (similar P0333 logic)) — Check Engine Light, VSC Off, VSC Trac lights on, with code P0333. No noticeable performance issues.
  ❌ Tried (didn't work) Replacing the fuel cap., Replacing both knock sensors with new parts.
  ✅ What actually fixed it The user cut back the Bank 2 knock sensor wire and replaced the pigtail harness connector using solder and shrink wrap. The code did not return, indicating the fault was in the heat-damaged connector, not the sensor itself.

OEM Part Supersession History

• 22060AA160 → 22060AA180 (for Japan-built vehicles) or 22060AA18A (for US-built vehicles) — The original sensor was prone to cracking from heat and vibration. The new part, originally for DIT (turbo) engines, offers improved durability and heat resistance.
  Heads up: While both new part numbers will likely function, the TSB specifies different parts for Japan-built (VIN starts with 'J') vs. US-built (VIN starts with '4S4') Imprezas. It is best practice to use the part specified for the vehicle's origin.

Model Year Variations Within This Range

• 2012-2017: Subaru specifies different replacement knock sensor part numbers based on the vehicle's assembly plant. Japan-built models use P/N 22060AA180, while US-built (SIA) models use P/N 22060AA18A. This is noted in TSB 07-133-18R.