OBD-II Fault Code Guide

P0328 Code: Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
Causes, Symptoms & How to Fix

Published: February 14, 2026 Last Updated: May 14, 2026 Verified by iCarsoft Tech Team 10 min read
Quick Summary

P0328 means the PCM is reading a knock sensor signal voltage that is too high — typically above 4–5V instead of the normal low varying AC signal. Without valid knock data the PCM retards ignition timing as a safety measure, causing reduced power and worse fuel economy. The most common fix is replacing the knock sensor ($30–$150 DIY) or repairing damaged wiring beneath the intake manifold. On many GM V8s, accessing the sensor requires intake removal, which raises labor costs significantly.

P0328 — Quick Reference
Definition Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
Severity Moderate — Reduced power, fuel economy loss, risk of detonation damage long-term
Trigger Knock sensor signal voltage stays above the PCM upper threshold (often >4–5V)
Location Engine block, intake valley, or cylinder head — Bank 1 (or single sensor on inline engines)
Common Vehicles GM (Silverado, Tahoe, Suburban), Toyota, Honda, Ford, BMW, Nissan, Hyundai, Volvo
Related Codes P0325, P0326, P0327, P0329, P0330, P0332, P1320
DIY Fix Cost $30–$150 (sensor)
Pro Fix Cost $150–$600 (sensor + labor; higher on GM V8 with intake removal)
Recommended Tool iCarsoft CR MAX BT

What Does P0328 Mean?

When your Check Engine Light is on and a scan returns P0328, the PCM is reporting that the primary knock sensor circuit is reading too high — voltage well above the expected range for a healthy knock signal. Most knock sensors are piezoelectric: they generate a tiny AC voltage in response to engine vibration, and the PCM uses that signal to detect detonation (knock) and retard ignition timing accordingly. A "high input" reading typically means the signal is pinned at the supply voltage instead of varying naturally.

  • "Sensor 1" identifies the primary knock sensor — on V engines, this is Bank 1 (the side containing cylinder #1). Inline engines often use a single sensor.
  • How the sensor works: a piezoelectric crystal mounted to the block converts vibration into a small voltage. The PCM filters this signal for knock-frequency content and adjusts timing in real time.
  • Why "high input" matters: a permanently high reading means the PCM cannot detect knock at all. As a safety fallback it retards timing globally — costing power and MPG until the fault is fixed.
Important first check: Verify which side of the engine is Bank 1 for your specific vehicle. Some manufacturers (notably GM and Nissan) number banks differently than others, and replacing the wrong-side sensor wastes time and money.

Symptoms of P0328

Symptoms of P0328 are usually mild but can become more pronounced under load:

  • Check Engine Light (MIL) on — the primary indicator. P0328 is stored as a continuous monitor fault.
  • Reduced engine power — the PCM retards timing in the absence of valid knock data, which softens throttle response and acceleration.
  • Worse fuel economy — retarded timing reduces combustion efficiency, often 1–3 MPG lower than usual.
  • Audible knock/ping under load — without active knock control, low-octane fuel or heavy throttle may produce a metallic pinging sound from the engine.
  • Limp/reduced power mode (some vehicles) — certain GM and Ford trucks will limit engine output if knock control is lost.
  • Failed emissions inspection — the illuminated MIL alone causes inspection failure in most regions.
Safety note: Driving for extended periods with P0328 under heavy load (towing, high RPM) can allow undetected detonation, which damages pistons and rod bearings over time. Repair within a few weeks at most.

Need to read knock sensor live data?

The iCarsoft CR MAX BT streams knock sensor voltage, ignition timing, and PCM knock retard values in real time — confirming the fault and verifying the repair once complete.

Send Inquiry →

What Causes P0328?

Five primary causes, ranked by frequency:

1

Failed Knock Sensor — Most Common

By far the most frequent cause. Knock sensors fail from heat soak, vibration fatigue, and on some GM engines from coolant or oil leaking onto the sensor (intake gasket seepage into the valley).

2

Open Circuit in Signal Wiring

The signal wire between the sensor and PCM can break or chafe — particularly where it passes the cylinder head or under the intake manifold. A broken signal wire often pulls the PCM input voltage to its reference high.

3

Short to Power on Signal Wire

If the signal wire shorts to a 5V reference or battery voltage anywhere in the harness, the PCM reads a pegged-high signal and stores P0328.

4

Damaged Connector / Corrosion

Oil-saturated or corroded connector pins disrupt the very small voltages produced by the sensor. Loose pins, green corrosion, and pushed-back terminals are common culprits.

5

PCM Failure — Rare

Internal PCM failures affecting the knock sensor input are uncommon but possible, especially after a jump-start mishap or water intrusion. Confirm only after wiring and sensor have been verified good.

Quick Diagnosis Decision Path — What did your scan return?

You have P0328 — check live data and pinpoint the signal type
↓
Branch A: Signal Pegged High
→ Open Wire or Failed SensorVoltage stays near supply. Unplug sensor — if voltage drops to spec, sensor is bad.
Branch B: Intermittent Spike
→ Wiring Chafe / ConnectorSpikes only under vibration or load. Inspect harness routing and connector pins.
Branch C: Oil/Coolant in Valley
→ Intake Gasket Leak (GM)Common on GM V8 — leaking gaskets soak the sensor and its harness. Repair the leak too.

How to Diagnose P0328 — Step by Step

Follow these steps in order to avoid replacing parts that won't fix the issue:

1
Read All Codes & Freeze Frame

Scan all modules and record every stored code, plus the freeze-frame data for P0328 (RPM, load, coolant temp). This shows the conditions under which the fault is set — a fault only at high RPM points toward intermittent wiring.

2
Visual Inspection

Locate the knock sensor (consult OEM info — many GM V8s have it under the intake manifold). Inspect for oil/coolant contamination, broken wires, bent connector pins, or damaged sensor housing. Address any leaks before testing further.

Pro tip: On GM LS-series engines, lift the intake manifold and check the valley pan — coolant pooled there is the #1 reason knock sensors fail prematurely.
3
Live-Data Knock Voltage

With the engine idling, watch the Knock Sensor Voltage PID. Healthy sensors typically read a low base voltage that rises slightly with engine activity. A reading stuck near 5V (or supply voltage) confirms an active P0328 condition.

4
Sensor Resistance Check

Unplug the connector. With a digital multimeter on Ohms, check across the sensor terminals — most piezo sensors read several thousand ohms (often 90 kΩ–5 MΩ depending on type; consult OEM spec). OL = open, 0 = shorted.

5
Wiring Continuity & Short Test

With the sensor unplugged and key off, check signal-wire continuity from the connector back to the PCM pin (consult wiring diagram). Then check that the signal wire is NOT shorted to power or ground. Wiggle the harness while testing to catch intermittents.

6
Tap Test for Sensor Response

With the sensor plugged in and engine idling, lightly tap the block near the sensor with a wrench (not on the sensor itself). A healthy sensor produces a brief spike in knock voltage on the scan tool. No response = sensor or wiring problem.

7
Clear Codes & Road Test

After repair, clear all codes and complete a drive cycle that covers light and heavy load. Verify the code does not return and that engine power and fuel economy normalize. P0328 should not reappear after one drive cycle.

Understanding Knock Sensor Live Data

Reading the knock sensor signal in real time is the fastest way to confirm the fault:

Knock Sensor Signal Behavior — What the Reading Tells You

Healthy: Low Base Voltage with Activity SpikesWithin Spec
Normal
P0328 Trigger: Voltage Pegged HighAlways above threshold
High Input
Intermittent: Random Spikes to 5VWiring chafe / loose connector
Wiring Issue
Knock Retard: Timing Pulled Way BackPCM compensation mode
Power Loss

* On a scope, the healthy knock signal looks like small AC ripples; a "high input" trace appears flat near 5V.

Quick test: Unplug the knock sensor with the key on. The PID should drop to near 0V; if it stays high, the fault is in the wiring or PCM, not the sensor.

How to Fix P0328

Option 1: Replace the Knock Sensor

Most common fix when resistance and tap testing confirm sensor failure. On most vehicles, replacement is straightforward — unbolt the old sensor, install the new one to OEM torque spec (over-tightening damages piezo sensors), and clear the code. On GM LS V8s, plan for intake manifold removal and budget for new intake gaskets while you're in there.

Option 2: Repair Wiring & Connectors

Splice broken signal wires using heat-shrink solder connectors. Clean oily connector pins with electrical contact cleaner, then apply dielectric grease. Re-route the harness away from heat sources or sharp edges, and add wire loom where it has been chafed.

Option 3: Address Underlying Leaks (GM-Specific)

If oil or coolant has saturated the sensor and harness, replacing the sensor alone won't last. Repair leaking intake or valve cover gaskets first, then install the new sensor on a dry, clean engine.

Option 4: PCM Diagnosis

Only after the sensor and wiring are confirmed good. Test the 5V reference and ground at the PCM connector, check for software updates (TSB-driven reflashes exist for some platforms), and only consider PCM replacement as a last resort.

Option 5: Use OEM-Quality Sensors

Cheap aftermarket knock sensors often produce out-of-range signals or fail again within months. Use OEM or OEM-equivalent (Bosch, Denso, NTK depending on platform) for lasting repair.

Repair Cost Breakdown

Repair DIY Cost Professional Cost Time
Knock Sensor Replacement — Most Common $30–$150 $150–$400 30–60 min (most)
Knock Sensor Replacement (GM LS V8 — intake off) $80–$250 $350–$600 2–4 hrs
Wiring / Connector Repair $10–$30 $100–$250 30–90 min
Intake Gasket Replacement (root-cause fix) $60–$150 $350–$800 3–5 hrs
PCM Reflash / Software Update — $80–$200 30 min
PCM Replacement (rare) $200–$700 $600–$1,500 1–2 hrs
Don't over-tighten: Knock sensors are piezoelectric and very torque-sensitive. Over-torquing damages the crystal and can cause an immediate repeat P0328 even with a brand-new sensor. Use a torque wrench.

Diagnose P0328 Accurately with iCarsoft CR MAX BT

Knock-related faults need real-time data to confirm the cause:

  • Live knock sensor voltage and PCM knock retard
  • Ignition timing and load PIDs side-by-side
  • Freeze-frame capture for intermittent faults
  • Full-system scan across engine, trans, and ABS
  • Code clearing once the repair is verified
  • Bluetooth wireless for under-hood diagnostics
Inquire Now →Contact us for business inquiries

P0328 on Common Vehicle Makes

P0328 patterns vary by manufacturer — knowing yours saves diagnosis time:

Chevrolet / GMC Very Common

  • Silverado, Sierra, Tahoe, Suburban, Avalanche — LS V8 sensors under intake
  • Coolant in the valley pan is the #1 root cause
  • Replace gaskets and harness extension at the same time

Ford Common

  • F-150, Mustang, Explorer — sensor on block, easier access
  • Often paired with rough idle codes if injectors are old
  • OEM Motorcraft sensors last longest

Toyota / Lexus Common

  • Tacoma, Tundra, 4Runner, RX, GX — V6 sensors deep in valley
  • Wiring sub-harness failures common after 100k miles
  • Use Denso OE replacements

Honda Moderate

  • Accord, Pilot, Odyssey, Ridgeline — V6 sensor under intake
  • Wiring chafe at intake manifold edge is common
  • Repair the harness when replacing the sensor

BMW Specific Pattern

  • E46, E60, E70, E90 — two knock sensors per bank on many
  • P0328 often pairs with P0332 on V8/V10 engines
  • Reflash may be required after sensor change

Other Makes Global

  • Reported on Nissan, Hyundai, Kia, Volvo, VW, Audi, and most modern gas engines.

How to Prevent P0328

  • Use the recommended fuel octane — chronic low-octane use forces constant knock retard and stresses the entire knock detection system.
  • Address oil and coolant leaks promptly — fluid contamination of sensors and harnesses is the leading cause of premature knock sensor failure.
  • Inspect wiring during major service — anytime the intake or valve covers come off, check the knock sensor harness for chafing and reroute if needed.
  • Replace harness extensions on GM V8s — the cheap pigtail extension is a known weak point; replace it whenever you change a knock sensor.
  • Use OEM-quality parts — cheap knock sensors often trip P0328 again within months.

P0328 often appears alongside these codes — the combination tells you exactly where to look:

P0325
Knock Sensor 1 Circuit Malfunction — general fault
P0326
Knock Sensor 1 Range/Performance — signal out of expected range
P0327
Knock Sensor 1 Circuit Low Input — opposite fault
P0332
Knock Sensor 2 Circuit Low Input (Bank 2)
P0333
Knock Sensor 2 Circuit High Input (Bank 2)

Frequently Asked Questions About P0328

Can I drive with P0328? ▾
Yes, short-term. Expect reduced power and 1–3 MPG worse fuel economy. Avoid heavy towing or sustained high RPM, because the PCM can't detect knock and detonation can damage the engine over time.
Will replacing the knock sensor fix P0328? ▾
Most of the time yes, but only after wiring and connector checks. On GM V8s in particular, the harness extension and connector fail more often than the sensor itself.
Why is P0328 so common on GM trucks? ▾
LS-series engines mount the knock sensors in the valley under the intake manifold. Any intake gasket or coolant crossover leak drips directly onto the sensors and harness, killing them prematurely.
Can bad gas cause P0328? ▾
Not directly. Low octane causes audible knock, which the PCM responds to by retarding timing — but it triggers range/performance codes (P0326), not high-input codes. P0328 is almost always electrical.
How much does P0328 cost to fix? ▾
Most vehicles: $150–$400 at a shop, or $30–$150 DIY for the sensor. GM V8s with intake removal: $350–$600 at a shop. Wiring repair alone is typically $100–$250.
Will P0328 cause my car to fail emissions? ▾
Yes. An illuminated MIL is an automatic inspection failure in most regions, regardless of the actual emissions output.
Can a weak battery cause P0328? ▾
Indirectly — very low system voltage can cause PCM input glitches that mimic sensor faults. Always confirm battery and charging system are healthy before deeper diagnosis.
Why is my engine sluggish with P0328? ▾
Without a valid knock signal, the PCM retards ignition timing as a safety measure. Less timing advance means less power and lower fuel economy — both return to normal once the code is fixed.
Does disconnecting the battery clear P0328? ▾
It temporarily clears the stored code, but the fault returns the next time the PCM tests the sensor circuit — usually within minutes of restarting. Fix the underlying issue.
Do I need a special tool to replace a knock sensor? ▾
Most use a standard deep socket. Some Toyota and Honda V6 sensors need a thin-wall socket because of clearance. Always torque to OEM spec — over-tightening destroys piezo sensors.

Verified by iCarsoft Automotive Technicians

This guide is based on OEM service procedures, dealer TSBs, and real-world repair data from GM, Ford, Honda, Toyota, and BMW platforms. Our technicians stress confirming wiring and sensor mounting torque before condemning the sensor.

Wrap-Up

P0328 is one of the most over-diagnosed codes in the field. The sensor often gets blamed when the real fault is in the wiring, connector, or — on GM V8s — a slow intake gasket leak. Confirm with live data and a tap test before reaching for parts.

  • Confirm which bank is "Bank 1" for your vehicle
  • Inspect for oil/coolant contamination before replacing
  • Torque the new sensor exactly to OEM spec
  • Verify the repair with a road test and live data

Was this P0328 guide helpful?

Share this guide:
Disclaimer: This guide is for reference only. Always verify diagnostic procedures and sensor specifications against the OEM service manual for your specific vehicle. iCarsoft Technology Inc. is not responsible for any vehicle damage resulting from repairs performed without proper training or equipment.