Knock Sensor 2 Circuit High Bank 2

What P0333 means

A knock sensor is a piezoelectric device threaded into the engine block that converts combustion vibration into a small voltage; as engine RPM rises and falls the sensor generates a signal that the PCM listens to inside a timed window around each cylinder's firing event to detect detonation (spark knock) and pull ignition timing back to protect the engine. On a V-configuration engine there are two of these sensors, one per bank, and P0333 is specific to knock sensor 2 on bank 2 — the bank whose cylinders do not include number 1. The code sets when the KS2 signal voltage climbs above the level the PCM calibrates for the current operating conditions, which the module reads as an electrical circuit fault (signal stuck or pulled high) rather than genuine knock. Because "circuit high" describes a voltage that is too high, Ford's own cause list for this exact code is short and specific: the KS2+ wire shorted to voltage, the KS2- wire shorted to voltage, or a damaged sensor — the same short-to-ground and open faults that dominate a plain "circuit" code like P0330 are not the primary suspects here. Ford also notes the truck may need to be driven for several minutes before P0333 confirms, so it often appears after a drive rather than the instant the key is turned. With the bank-2 knock signal untrusted, the PCM falls back to a conservative timing map on that bank, costing a little power and economy and removing detonation protection where it can no longer hear knock.

Symptoms

• Check-engine light on, frequently appearing only after the vehicle has been driven for several minutes rather than at key-on
• Slight loss of power and duller throttle response as the PCM retards ignition timing to a safe default without trustworthy bank-2 knock feedback
• A small drop in fuel economy from the more conservative timing the computer falls back on
• Audible pinging or knock under load and hard acceleration if real detonation on bank 2 is no longer being corrected
• Often no obvious driveability complaint at all, with the stored code being the only sign anything is wrong

Common causes

• The KS2+ signal wire shorted to voltage — chafed against a powered circuit or backfeeding another wire — pulling the reading high (Ford's leading cause for P0333)
• The KS2- signal wire shorted to voltage, doing the same to the return side of the circuit
• A failed or internally damaged knock sensor 2 whose output has drifted high or out of range (Ford spec: the sensor's internal resistance should read about 4.39-5.35 MΩ)
• A corroded, oil- or coolant-contaminated KS2 connector bridging the terminals to a source of voltage
• Chafed or pinched harness insulation on the bank-2 knock circuit where it routes near powered wiring in the engine valley
• A backfeed or wiring error after recent engine work near the intake or coil-on-plug harness that lets voltage reach the KS2 lines
• Rarely, a PCM/internal driver fault on the knock-sensor input circuit

Severity & driving advice

Severity: Moderate — The engine still runs, but with the bank-2 knock signal untrusted the PCM retards timing (some lost power/economy) and loses detonation protection.

Can I drive? Usually safe to drive short-term; the main risk is that real knock on bank 2 is no longer corrected, so avoid low-octane fuel and hard acceleration and repair it soon to restore full timing and power.

Diagnostic approach

1. Scan codes and read freeze-frame — Pull every stored and pending DTC first. Note any companion knock codes — the bank-1 family (P0325/P0327/P0328) or the other bank-2 code P0330/P0331 — plus misfire or timing codes, since those change the diagnostic path. Read the freeze-frame for RPM, load, and temperature when P0333 set, because Ford notes this code often needs the engine driven under load for several minutes before it confirms.
2. Confirm the sensor location and inspect the bank-2 connector — Identify bank 2 as the cylinder bank that does not contain cylinder 1, and locate knock sensor 2 on that side of the block (on many Ford V8s the knock sensors sit in the valley beneath the intake at connector C108). Because P0333 is a "high" fault, look hard for anything that could feed voltage into the circuit: corrosion or oil intrusion in the KS2 connector, spread or bridged terminals, and any section of the two-wire harness chafed against a powered wire.
3. Check the KS2 wiring for a short to voltage — This is the core test for a "circuit high" code. Disconnect the KS2 sensor and the PCM connector, then, key on and engine off, measure voltage from each KS2 wire (KS2+ and KS2-) to ground. Any voltage present on either wire with both ends unplugged reveals the short to voltage that Ford lists as the primary cause. Trace and repair the chafe or backfeed, then clear the codes and rerun the self-test.
4. Check the sensor's internal resistance — With the KS2 connector unplugged, measure resistance across the two sensor (component-side) terminals. A healthy flat-response knock sensor is a very high-impedance device; Ford's chart expects roughly 4.39 to 5.35 MΩ. A reading well outside that window condemns the sensor, so replace it, clear the codes, and rerun the self-test to confirm the fix.
5. Rule out a short to ground and an open, then verify continuity — Although short-to-voltage is the prime suspect, confirm the rest of the circuit is clean: with the sensor and PCM unplugged, resistance from each KS2 wire to ground should read greater than about 10K ohms (a low value would be a short to ground), and continuity along each KS2 wire from the sensor connector to its PCM pin should be under about 5 ohms end-to-end. Repair any fault found before proceeding.
6. Wiggle-test for intermittents, then confirm the repair — If everything measures good but the code returns, back-probe the KS2 circuit and flex, wiggle, and bend short sections of the harness from the sensor to the PCM while watching for the reading to jump high, which exposes an intermittent short to voltage. Once the wiring, connector, and sensor all check out and any fault is repaired, clear the codes and road-test the truck for several minutes under load — the interval Ford says it can take to set — to confirm P0333 does not reset.

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