OBD-II trouble code
P0328: Knock Sensor 1 Circuit High (Bank 1 or Single Sensor)
The bank 1 knock sensor signal voltage is pinned at or near the upper threshold — usually because something has shorted the signal wire to the 5V reference, or the sensor itself has failed in a way that pegs its output high. Less common than P0327, and more often a wiring fault than a sensor fault.
Quick facts
- System
- Powertrain
- Category
- Knock & Other
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $800
- DIY difficulty
- Intermediate DIY
Browse every code in P0300–P0394, or start from the full code library.
What does P0328 mean?
P0328 is the high-signal partner to P0327. Where P0327 sets when the knock sensor signal drops below the minimum acceptable voltage (suggesting an open circuit or dead sensor), P0328 sets when the signal climbs above the maximum acceptable voltage (suggesting a short to reference voltage or a sensor stuck in a high-output state). The PCM uses both bounds to validate that the signal it's receiving could plausibly be a real knock-sensing measurement.
For most readers, the practical question is which failure is more likely: sensor or wiring. With P0328, the odds shift toward wiring more than with P0327. A failing knock sensor most often produces a low or absent signal, not a pegged-high signal — the piezo crystal failure mode tends to drop voltage rather than raise it. A pegged-high signal usually comes from either a short between the signal wire and a 5V reference somewhere in the harness, or a sensor that has cracked internally and is producing electrical noise that reads as a constant high signal.
The diagnostic discipline matters because the labor depth on knock sensor replacement is platform-dependent. On GM LS trucks (Silverado, Tahoe, Yukon, Suburban with the 4.8L/5.3L/6.0L), pulling the intake manifold to replace a knock sensor is a 3-4 hour job. If the actual fault is a $20 connector pigtail, you don't want to do that job and still have the code. Inspect wiring and connector carefully before condemning the sensor.
Like P0327, the drivability impact is mild. The engine runs because knock sensing is a protection layer rather than a critical input. What you lose is the PCM's ability to optimize ignition timing under normal conditions and detect detonation under abnormal conditions. Power and fuel economy take a small hit, and the long-term risk is undetected detonation under marginal fuel or heavy load conditions.
One pattern is worth recognising, and it needs stating carefully because it is widely stated wrongly. A piezoelectric knock sensor is a generator rather than a powered sensor: it makes its own signal from mechanical stress, has no 5V supply pin, and shares no sensor reference with the MAP or throttle position sensor. What it does share is loom. Its signal conductor is routed in the same bundle as the 5V reference feeding those sensors, so a chafe or a wet connector that bridges the two pulls the knock input high and upsets the genuinely 5V-referenced inputs at the same moment. That is why P0328 arriving alongside MAP or throttle position codes points at a damaged harness section or a failed common ground rather than at the knock sensor — what the faults have in common is wiring, not a supply the knock sensor was ever given.
Common causes
- Wiring chafe damage shorting the knock sensor signal wire to a 5V reference circuit
- Failed knock sensor with internal short (less common than the P0327 failure mode)
- Cracked piezo element producing electrical noise that reads as pegged-high
- Corroded knock sensor connector with a leakage path from the signal pin to its neighbour
- Knock signal conductor bridged to a 5V reference inside a shared loom section, which disturbs the genuinely 5V-referenced sensors at the same time
- Aftermarket knock sensor of wrong specification
- PCM internal fault on the signal-input circuit (rare)
- Recent harness work where the signal wire was crossed with a reference wire during repair
Symptoms
- Check Engine Light on
- Mild loss of power, particularly under acceleration
- Reduced fuel economy
- Engine sounds normal in most cases
- Possible additional sensor codes if a shared 5V reference is involved
- Slightly delayed throttle response on some platforms
Diagnostic steps
- 1.Pull all codes. P0328 alone is the bank 1 specific case. P0328 with codes for MAP, TPS or other 5V-referenced sensors points at a damaged loom section or a common ground rather than at the knock sensor — those sensors share routing with the knock signal wire, not a supply with the sensor itself.
- 2.Do not treat sensor disconnection as a pass/fail test on a high-signal code. A knock input is high-impedance, so unplugging the sensor removes the only load holding it down and the high code can set with the sensor out of circuit whether or not the harness is faulty. Note what happens, but settle it with the continuity measurement below rather than with the code status.
- 3.With the sensor disconnected, check the signal wire voltage at the sensor connector — but treat a high reading as a lead rather than a verdict. A knock input is high-impedance, and an unloaded one can sit well above where it rests with the sensor attached, so a raised voltage here is suggestive and not conclusive. Confirm it by disconnecting both ends and checking for continuity between the signal wire and the nearest 5V reference: that is a short you can prove instead of infer.
- 4.Inspect the harness routing from the knock sensor toward the PCM — check chafe points, sharp bends, and locations where the harness contacts metal brackets.
- 5.Test the knock sensor by measuring resistance across its terminals and compare to OEM spec. A reading well outside the figure suggests the element has failed internally — but an in-spec reading clears nothing, because a piezo element fails by losing output rather than by changing resistance. To show the sensor is still alive, leave it unplugged, set the meter to AC millivolts across its terminals and tap the block nearby: a healthy sensor answers with a brief pulse. Many handheld meters sample too slowly to catch it, so a flat reading on a cheap meter is inconclusive rather than a condemnation.
- 6.Check connector pins for green corrosion or pushed-back terminals.
- 7.If the wiring tests clean and the sensor measures in-spec, the fault is intermittent — clean the connector, ensure tight contact, and clear the code to retest.
- 8.Replace the sensor only after confirming the wiring isn't the actual fault. Wrong-fault repairs are expensive on platforms where the sensor is buried.
Repair cost
$100 – $800
Wiring repair is $100-400 depending on access and how deep the harness damage runs. Connector pigtail replacement is $80-250. Knock sensor itself runs $30-150 in parts. On accessible platforms (Subaru, Nissan VQ, some Honda V6) total sensor replacement is $150-300. On GM LS trucks where the sensor sits under the intake manifold, expect $500-800 because intake removal dominates labor. As with P0327, replace both sensors at once on V-engines if the labor demands intake removal.
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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.