P0333 – Knock Sensor 2 Circuit High Bank 2

P0333 – Knock Sensor 2 Circuit High Input (Bank 2) means the engine control unit has detected a knock sensor signal that is higher than the expected voltage range for Knock Sensor 2 on Bank 2. This sensor monitors detonation on the opposite engine bank from Knock Sensor 1. A high input usually indicates a wiring short, excessive sensor output, or moisture/corrosion in the connector. This guide explains what P0333 means, symptoms, causes, diagnostics, and the most effective repair solutions for restoring proper knock control.

What Does P0333 Mean?

P0333 is a generic OBD-II trouble code that indicates Knock Sensor 2 on Bank 2 is sending a voltage signal that is abnormally high. Instead of responding normally to engine vibration, the sensor produces a signal that spikes or stays elevated. This may trick the ECU into detecting false knock or cause the ECU to ignore real knock events entirely.

As a safety precaution, the ECU typically retards ignition timing on Bank 2, which reduces engine performance and fuel efficiency until the issue is repaired.

Quick Reference

• OBD-II Family: P-Code (Powertrain)
• Scope: Generic
• System: Knock Sensor / Ignition Timing Control
• Difficulty Level: Moderate
• Estimated Repair Cost: €90–€360+
• Last Updated: 10 December 2025

Real-World Example / Field Notes

An SUV came in with poor acceleration and rough engine behavior at high RPM. Live data showed constant high knock sensor voltage on Bank 2. The wiring harness had rubbed against a metal bracket, creating a short to the 5V reference circuit. Repairing the damaged section resolved the false high-input reading.

In another case, a V6 engine repeatedly set P0333 due to water accumulation inside the knock sensor connector after a coolant hose leaked onto the harness. Cleaning and sealing the connector fixed the problem permanently.

Symptoms of P0333 – Knock Sensor 2 High Input

• Sluggish acceleration: ECU retards timing to prevent potential knock.
• Poor fuel economy: Reduced timing advance lowers efficiency.
• Pinging or knocking: Possible if ECU misinterprets the signal.
• Rough running: Especially under heavy load or high RPM.
• Intermittent hesitation: Timing may fluctuate as ECU compensates.
• Check engine light: Triggered when high voltage input is detected.

Common Causes of P0333

Most Common Causes

• Short to voltage in Knock Sensor 2 wiring
• Failed or overly sensitive knock sensor
• Corroded or moisture-contaminated connector
• Improperly torqued knock sensor
• Poor engine grounding

Less Common Causes

• ECU internal fault
• Engine mechanical noise interpreted as knock
• Aftermarket tuning altering knock sensitivity
• Low-octane fuel causing severe knock
• Heat-damaged wiring insulation

Diagnosis: Step-By-Step Guide

Diagnosing P0333 requires checking for wiring shorts, improper mounting, and abnormal knock sensor output patterns.

Tools You’ll Need

OBD-II scanner, multimeter, wiring diagrams, torque wrench, mechanic’s stethoscope, and basic tools.

1. Review freeze-frame data: Check RPM, load, and temperature when the fault occurred.
2. Inspect wiring harness: Look for exposed wires contacting metal or 5V reference circuits.
3. Check connector condition: Look for corrosion, coolant, or moisture.
4. Measure signal voltage: High readings at idle indicate electrical faults.
5. Test sensor resistance: Compare to factory specs for Bank 2.
6. Verify torque: Over-tightening increases sensor sensitivity.
7. Clean mounting surface: Ensure proper contact.
8. Inspect grounds: Weak engine grounds can elevate sensor voltage.
9. Check for real knock: Severe detonation may trigger high input readings.
10. Check ECU update availability: Some vehicles revise knock-control logic.

Pro Tip: If the knock sensor wiring is shorted to a 5V reference source, P0333 will typically set immediately on startup before the engine even begins to knock — a clear sign of electrical failure rather than real detonation.

Possible Fixes & Repair Costs

• Repair shorted wiring: €50–€150
• Replace Knock Sensor 2: €70–€180
• Replace or repair connector: €40–€120
• Correct mounting torque: €0–€50
• Clean block mounting surface: €0–€40
• Improve engine grounding: €20–€80
• ECU reflash (rare cases): €50–€120

Can I Still Drive With P0333?

Driving is usually possible, but performance will be reduced because the ECU retards timing to protect the engine. Avoid heavy acceleration, high RPM, towing, or steep climbs until the issue is repaired. Prolonged driving with P0333 can increase the risk of detonation-related engine damage if the ECU misinterprets knock events.

Last updated: March 1, 2026