OBD-II trouble code
P0333: Knock Sensor 2 Circuit High (Bank 2)
SAE J2012: Knock Sensor 2 Circuit High (Bank 2). The signal is above the high threshold. Which fault — open, short to ground, or short to voltage — sets the high code is in this engine's chart. It is not an open on every engine.
Quick facts
- System
- Powertrain
- Category
- Knock & Other
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $400 – $600
- DIY difficulty
- Intermediate DIY
Browse every code in P0300–P0394, or start from the full code library.
What does P0333 mean?
P0333 is the bank-2, high-input knock sensor code, and the most useful way to read it is in contrast with its low-input twin, P0332. Both codes involve the same sensor on the same bank — the piezo accelerometer bolted to the bank-2 side of the block that listens for detonation so the PCM can pull timing to protect the engine. P0332 is the low code on this bank and P0333 is the high code. The diagnostic chart for this engine says whether an open, a short to ground, or a short to voltage stores the high code. Do not start the intake-off job on the assumption that high means open.
Bank 2 is the bank that does not contain cylinder 1. The service information shows which side that is. GM LS and Ford Modular do not share one passenger-side rule.
GM bulletin 02-06-04-023, reprinted by Brake & Front End, covers water in the rear knock-sensor cavity setting P0332 on the engines that reprint names: 1998–2002 Camaro, Corvette, and Firebird 5.7L LS1, and 1999–2002 Silverado, Suburban, Tahoe, Sierra, Yukon, and Yukon XL, plus 2002 Avalanche and Escalade, with the listed 4.8L, 5.3L, or 6.0L. The repair is the rear sensor at 20 Nm (15 lb ft), an RTV dam left open at the rear, and removal of the rear foam seal. It does not name P0333, it does not run through 2007, and it does not say to replace both sensors.
The engine runs on a conservative spark map while the circuit is distrusted. There is no published fuel-economy penalty.
Common causes
- Open circuit in the bank-2 knock sensor wiring — broken or chafed-through signal wire
- Disconnected or corroded connector that has lost continuity (common on GM LS trucks)
- Bank-2 knock sensor failed open internally
- Corroded sensor and connector from water pooling in the under-intake wells on GM LS engines
- High resistance in the circuit from corroded pins or a poor ground
- Loose sensor that has lost mechanical and electrical contact
- Aftermarket knock sensor of incorrect specification or resistance
- PCM signal-input fault (rare)
Symptoms
- Check engine light on with P0333 stored
- Mild loss of power, especially under acceleration
- Reduced fuel economy
- Slightly delayed throttle response
- Possible audible pinging under heavy load if real detonation goes undetected on bank 2
- Engine otherwise sounds and runs normally
Diagnostic steps
- 1.Confirm which physical bank is bank 2 on your engine — the head without cylinder 1 — using the firing-order diagram for your specific engine.
- 2.Pull all codes. P0333 alone is the classic bank-2 open-circuit case. P0333 with P0332 or the bank-1 codes can point at shared wiring or a PCM-side issue.
- 3.Because 'high input' suggests an open, start at the connector: inspect for corrosion, a backed-out or broken pin, or a connector that has worked loose. On GM LS trucks, expect to remove the intake to reach it.
- 4.Disconnect the bank-2 knock sensor connector and measure resistance across the sensor terminals — but look up the spec for your actual part number before drawing a conclusion. Knock sensors come in resonant and wide-band piezoelectric designs and the published values differ enormously between them: some are specified in hundreds of ohms, others in the megohm range, and for some the service procedure treats a very high reading as the correct result and continuity as the failure. An out-of-spec reading condemns the sensor; an open reading only condemns it if the spec for that part gives a finite value. Where no spec is available, the resistance check proves nothing in either direction and the sensor has to be judged another way.
- 5.A meter cannot see the sensor's actual output — a piezo element produces a short burst of AC that a DMM will not resolve — so if the resistance check is inconclusive, verify the circuit instead and then judge the sensor by what the engine does: watch the scan tool's knock-retard or knock-count parameter under load, or look at the sensor on a scope. Back-probe the signal wire from sensor to PCM and check for an open or high resistance along the run.
- 6.Check the sensor ground and mounting — a loose sensor or poor ground can read as high input.
- 7.Torque the sensor to the figure in the service information. On the engines in GM bulletin 02-06-04-023 that figure for the rear sensor is 20 Nm (15 lb ft), and the bulletin replaces that one sensor. Do not replace the other sensor unless the inspection or a bulletin says so.
- 8.Clear the code, drive through a heavy-load pull, and confirm it stays off.
Repair cost
$400 – $600
Parts plus labor. RepairPal's national average for a knock sensor is about $417–$589, rounded to $400–$600. A connector repair is wiring labor. The bulletin's 20 Nm torque and single rear sensor apply only to the vehicles in 02-06-04-023, and that bulletin's code is P0332.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with knock sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
Related repairs
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.