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
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.
On certain platforms (some Nissan VQ-series, some older Honda V6, some Mazda L-series), the knock sensor share a 5V reference circuit with other sensors. When P0328 sets alongside codes for the MAP sensor, throttle position sensor, or other 5V-referenced inputs, the cause is usually a shorted reference circuit somewhere in the harness rather than the knock sensor itself.
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 high-resistance path between signal and reference pins
- Shared 5V reference circuit fault affecting multiple sensors at once
- 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 shared reference circuit fault — not the knock sensor itself.
- 2.Disconnect the knock sensor connector and observe whether the code clears or behavior changes. If the same code persists with the sensor disconnected, the fault is in the harness.
- 3.With the sensor disconnected, check the signal wire voltage at the sensor connector. A signal wire that already reads near 5V with no sensor connected has a short to reference somewhere upstream.
- 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 the sensor terminals. Compare to OEM spec. Out-of-spec resistance suggests the sensor has failed internally.
- 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.
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.