P0328
Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)P0328 is a generic OBD-II powertrain diagnostic trouble code: Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0328 means
P0328 is set when the PCM detects that the voltage from knock sensor 1 on bank 1 (or the single-bank sensor) is consistently above the manufacturer's maximum acceptable threshold — commonly above approximately 4.5 V on a 5 V reference circuit. This is the electrical mirror of P0327: where P0327 indicates a signal stuck low, P0328 indicates a signal stuck high, pointing to an open circuit, a short to the reference voltage, or a failed sensor producing an abnormally elevated output.
The knock sensor's signal wire normally rides at a low voltage (close to the reference mid-point on some resonant sensor designs, or near 0 V on flat-response types) and produces brief AC voltage spikes when engine knock vibrations are sensed. If the PCM reads a consistently elevated DC voltage with no detonation-consistent variation, it concludes the circuit has failed high. Possible mechanisms include: an open ground path allowing the signal line to float to the reference rail, a sensor with an internal failure bridging the signal to the supply, or a wiring fault that connects the signal wire to a voltage source.
A persistent high-side fault means the knock monitoring feedback loop is broken. The PCM typically responds by applying conservative (retarded) ignition timing as a protective default, reducing power and economy. Real knock events will not be detected or corrected. Additionally, because the circuit fault can mimic constant high-amplitude knock, some PCM calibrations may interpret P0328 as an overheating or fuel-quality warning and further restrict engine output.
Engine overheating and low-octane fuel use can exacerbate the condition by generating genuine high-frequency vibration that the sensor reports — even a partially functional sensor may produce an above-threshold voltage if the engine is operating under severe detonation conditions. Diagnosis must therefore include ruling out real engine knock, cooling system faults, and fuel quality before condemning the sensor or wiring.
Common causes
Most-frequently reported root causes when P0328 is logged.
-
1
Defective knock sensor (internal failure producing elevated output)
-
2
Open ground path in the knock sensor circuit (signal floats high)
-
3
Signal wire shorted to the 5 V reference or battery voltage
-
4
Corroded or damaged sensor connector allowing voltage cross-contamination
-
5
Engine overheating generating sustained high-amplitude vibration
-
6
Incorrect fuel octane causing persistent detonation
-
7
Fuel system fault (low fuel pressure, lean mixture) causing abnormal combustion
-
8
PCM internal fault on the knock sensor input circuit (rare)
Symptoms drivers notice
How to diagnose P0328
A typical diagnostic flow when this code is present.
-
1
Scan all stored and pending codes; pay particular attention to concurrent cooling system, fuel trim, or misfire codes that could indicate genuine knock conditions
-
2
Check freeze-frame data — note coolant temperature and fuel trims at fault time to rule out overheating or lean-condition contributions
-
3
Visually inspect the knock sensor, connector, and wiring for damage, corrosion, or contact with hot surfaces or moving parts
-
4
Unplug the sensor and measure resistance across its terminals; compare to OEM specification (an open reading or reading far above spec indicates a failed sensor)
-
5
With the sensor unplugged, check the signal wire at the PCM connector for a short to the reference voltage or battery positive
-
6
Verify engine cooling system function — confirm coolant level, thermostat operation, and that the engine is not overheating during the test drive
-
7
Verify correct fuel octane is being used; if suspect, drain and refill with premium and retest
-
8
If sensor and wiring test normal, monitor knock sensor voltage live on a scope during a test drive — isolate whether high reading occurs at specific RPM/load points suggesting real detonation vs. constant rail-high
Related powertrain codes
Frequently asked questions
What is the difference between P0326, P0327, and P0328?
P0326 = knock sensor signal out of expected range or erratic (performance fault). P0327 = signal consistently too low (stuck low, short to ground or failed sensor with no output). P0328 = signal consistently too high (stuck high, open ground or short to voltage). All three disable active knock correction and trigger conservative timing.
Could P0328 mean there is real engine knock happening?
Yes. While the code is often a sensor or wiring fault, real sustained detonation caused by overheating or low-octane fuel can drive the sensor output above the PCM's acceptance threshold and trigger P0328. Always rule out genuine knock, cooling faults, and fuel quality before condemning the sensor.
Is P0328 more urgent than P0327?
Both carry the same practical risk — loss of knock correction. P0328 is sometimes harder to diagnose because it requires ruling out genuine knock as a cause. In terms of urgency, treat both as requiring prompt attention to avoid potential engine damage from undetected detonation.
Can a faulty coolant temperature sensor trigger P0328?
Not directly — P0328 is specific to the knock sensor circuit voltage. However, a faulty coolant temperature sensor can mask an overheating condition, which can then cause genuine knock that drives the knock sensor signal high. Checking all related codes in context is important.
Does P0328 affect automatic transmission behavior?
On some vehicles, the PCM shares knock sensor data with the transmission control module (TCM). Persistent knock sensor faults can result in the TCM applying conservative shift strategies or holding lower gears to reduce engine load, which may be perceived as sluggish or unexpected shifting behavior.
Disabling P0328 in software
RaceTune can permanently disable P0328 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0328 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file