Knock sensor 2 signal wire shorted to voltage or chafed against a 12-volt source; Failed knock sensor 2 internally shorted, often due to cracked housing or coolant intrusion; Corroded, pushed-back, or water-filled connector at the knock sensor or harness junction; Open or high-resistance ground path for the sensor, causing the signal to float high; Harness damage from heat, rodent chewing, or routing against a hot exhaust component; PCM internal fault or corrupted knock sensor signal processing circuit; Aftermarket engine work or a replacement sensor with incorrect resistance characteristics

DTC codes / P03xx · Ignition system and misfire / P0333

P0333Knock Sensor 2 Circuit High

Q: What does code P0333 mean?

Knock Sensor 2 Circuit High. P0333 means the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit of knock sensor 2, which is the sensor monitoring the second bank of cylinders on V-type engines. The PCM expects the sensor to produce a small alternating voltage that rises with knock, but instead it sees a signal stuck near the top of its range, so it flags the circuit as high.

P0333 means the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit of knock sensor 2, which is the sensor monitoring the second bank of cylinders on V-type engines. The PCM expects the sensor to produce a small alternating voltage that rises with knock, but instead it sees a signal stuck near the top of its range, so it flags the circuit as high.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode if the PCM defaults to a conservative spark strategy
Audible engine knock or pinging under acceleration because timing is no longer being actively retarded
Poor fuel economy and sluggish throttle response as the PCM pulls timing defensively
Rough running or hesitation on some vehicles when the fault affects the knock control strategy
In rare cases, a no-start or stalling condition if the shorted signal corrupts shared sensor reference voltage

Common causes, most likely first

Knock sensor 2 signal wire shorted to voltage or chafed against a 12-volt source
Failed knock sensor 2 internally shorted, often due to cracked housing or coolant intrusion
Corroded, pushed-back, or water-filled connector at the knock sensor or harness junction
Open or high-resistance ground path for the sensor, causing the signal to float high
Harness damage from heat, rodent chewing, or routing against a hot exhaust component
PCM internal fault or corrupted knock sensor signal processing circuit
Aftermarket engine work or a replacement sensor with incorrect resistance characteristics

How to diagnose and fix it

Scan all modules and record freeze-frame data to confirm P0333 is active and not a history code from a previous repair
Inspect the knock sensor 2 connector and harness for corrosion, pushed terminals, chafing, and heat damage
Measure signal circuit voltage with the key on and sensor connected, comparing it to the expected bias voltage for that platform
Check the sensor ground circuit for excessive resistance and verify the sensor mounting surface is clean and torqued correctly
Swap knock sensor 2 with knock sensor 1 where accessible to see whether the fault follows the sensor or stays with the circuit
Perform a resistance and tap test on the suspect sensor and compare it to the known-good bank
Repair or replace the faulty harness section, connector, or sensor, then clear codes and verify the signal with a scan tool during a road test

What a high knock signal really means

A high signal voltage does not automatically mean the sensor is bad; a short to voltage on the signal wire or a bad ground will produce the same code and replacing the sensor will not fix it.
On many V-type engines the knock sensors sit under the intake manifold in a valley that collects water and debris, so coolant or oil intrusion into the connector is a frequent cause that visual inspection from above misses.
Technicians sometimes chase P0333 as a spark knock problem and replace plugs or fuel, but the code is an electrical circuit fault and will not clear until the voltage abnormality is corrected.
A loose or over-torqued knock sensor can generate a false high signal because the piezoelectric element depends on correct clamping force to read vibration accurately.
Shared reference voltage circuits can drag the knock signal high when another sensor on the same circuit shorts, so check for companion codes before condemning the knock sensor.

Can I keep driving with P0333?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration and towing because the PCM may no longer retard timing properly and prolonged knock can damage pistons. If the engine is audibly pinging or the vehicle enters limp mode, keep speeds low and schedule diagnosis promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.