P0328 Code: Knock Sensor 1 Circuit High – Causes & Fixes

What Is Code P0328?

The P0328 diagnostic trouble code stands for “Knock Sensor 1 Circuit High Input Bank 1.” This code is triggered when your vehicle’s engine control module (ECM) detects that the knock sensor on Bank 1 is sending a voltage signal that exceeds the manufacturer’s specified range. The knock sensor is a critical component that detects engine detonation (pre-ignition or “knocking”) and helps the ECM adjust ignition timing to prevent engine damage.

What Does P0328 Mean?

The knock sensor works by detecting vibrations caused by abnormal combustion in the engine cylinders. When it detects knock, it sends a signal to the ECM, which responds by retarding (delaying) the ignition timing to prevent damage. A “high input” signal means the voltage being sent to the ECM is higher than the normal operating range (typically above 4.5-5 volts, depending on the vehicle).

Bank 1 refers to the side of the engine that contains cylinder number 1. Most vehicles have two knock sensors—one on each bank—to monitor both sides of the engine independently. When the ECM receives a signal that’s consistently too high, it sets the P0328 code and illuminates the check engine light.

This is different from a low signal (P0327), which indicates the opposite problem—a signal voltage that’s too low.

Common Symptoms

• Check Engine Light: The most obvious symptom; the light will remain on until the code is cleared
• Engine Knocking or Pinging: You may hear a metallic knocking sound, especially under acceleration or load
• Reduced Engine Performance: The engine may run in “limp mode,” with limited power and reduced fuel efficiency
• Rough Idle: The engine may feel unstable or rough when idling
• Difficulty Starting: In some cases, the vehicle may be hard to start or crank slowly
• Decreased Fuel Economy: The ECM may adjust fuel injection and timing, reducing efficiency
• No Noticeable Symptoms: Some drivers experience no symptoms other than the check engine light

Possible Causes (Ranked by Frequency)

1. Faulty Knock Sensor: The most common cause. The sensor itself may be failing, producing an abnormally high voltage signal even at idle.
2. Damaged Wiring or Connectors: Corroded, pinched, or damaged wires in the knock sensor circuit can cause signal voltage problems. A short to power can cause a high signal.
3. Poor Electrical Connection: A loose or corroded connector at the knock sensor or ECM can result in intermittent or incorrect signals.
4. Engine Control Module (ECM) Malfunction: Rarely, the ECM itself may be faulty and unable to properly interpret the knock sensor signal.
5. Shielding Issues: Damaged or missing shielding around the knock sensor wiring can allow electromagnetic interference, causing signal distortion.
6. Defective Knock Sensor Connector: A cracked or damaged connector housing can allow moisture and corrosion, affecting signal quality.
7. Engine Mechanical Problems: In rare cases, actual engine knock from carbon buildup or incorrect fuel octane can trigger the sensor repeatedly, though this usually produces a low signal code.

Diagnostic Steps

Follow these steps to diagnose the P0328 code:

Step 1: Scan for Additional Codes

Use an OBD-II scanner to read all stored and pending codes. Note if there are other knock sensor codes (P0327, P0332, P0333) or engine control codes that might provide additional clues.

Step 2: Visual Inspection

Locate the knock sensor on Bank 1 (consult your vehicle’s service manual for the exact location—typically on or near the engine block). Inspect:

• The sensor body for cracks or damage
• The connector for corrosion, moisture, or loose pins
• The wiring harness for cuts, pinches, or abrasions
• Any signs of water intrusion or corrosion

Step 3: Check Connector and Wiring

Disconnect the knock sensor connector and inspect the pins. Look for:

• Green or white corrosion (oxidation)
• Bent or pushed-back pins
• Moisture inside the connector

If corroded, clean the connector with electrical contact cleaner and a small brush. Reconnect and retest.

Step 4: Measure Sensor Voltage

Using a digital multimeter set to DC voltage, measure the voltage at the knock sensor connector with the engine off. Normal voltage should be between 0-5 volts. If you’re reading above 5 volts consistently, the sensor or wiring is likely faulty.

Step 5: Test Sensor Resistance

Set your multimeter to resistance (ohms) mode. Disconnect the sensor and measure its resistance. Typical knock sensor resistance ranges from 200,000 to 900,000 ohms, depending on the vehicle. Consult your service manual for the exact specification. A reading outside this range indicates a faulty sensor.

Step 6: Check for Shorts to Power

With the key off and the sensor disconnected, use your multimeter to check for continuity between the sensor signal wire and the positive battery terminal. There should be no continuity. If there is, you have a short to power in the wiring harness.

Step 7: Test with Engine Running

If initial tests are inconclusive, connect your scanner to monitor the knock sensor signal voltage while the engine is running. The voltage should fluctuate as the engine operates. A steady, unchanging high voltage suggests a sensor or wiring problem.

Step 8: Replace and Retest

If all tests point to a faulty sensor, replace it with a manufacturer-approved part. Clear the code and test drive the vehicle to confirm the fix. If the code returns, the problem may be in the wiring or ECM.

Repair Cost Estimates

The cost to repair a P0328 code varies depending on the underlying cause and your vehicle:

• Knock Sensor Replacement: $150–$400 (parts + labor). The sensor itself typically costs $50–$150, with labor ranging from $100–$250 depending on accessibility.
• Wiring Repair or Connector Replacement: $100–$300. If the issue is a damaged wire or connector, repairs are usually less expensive than a sensor replacement.
• Electrical Diagnosis: $75–$150. If you need a professional to diagnose the problem, expect a diagnostic fee.
• ECM Replacement (rare): $800–$1,500+. If the ECM is faulty, replacement is expensive and may require reprogramming.

Note: Costs vary significantly by vehicle make and model. Luxury and European vehicles typically cost more. Always get a quote from your mechanic before authorizing repairs.

Can I Still Drive?

Yes, you can typically drive with a P0328 code, but with caution:

• Severity: This code is generally considered moderate. It’s not an emergency, but it should be addressed soon.
• Engine Damage Risk: If the knock sensor is not functioning correctly, the ECM cannot detect actual engine knock. This means your engine could experience detonation without the ECM adjusting ignition timing, potentially causing internal damage over time.
• Performance Impact: Your vehicle may run in limp mode with reduced power and fuel efficiency.
• Recommendation: Drive carefully and avoid aggressive acceleration or towing until the code is diagnosed and repaired. Have the issue inspected by a qualified mechanic within a few days.

Frequently Asked Questions

Can I clear the P0328 code myself?

You can clear the code using an OBD-II scanner, but this is only a temporary fix. The code will return if the underlying problem isn’t addressed. Clearing the code without fixing the issue means the ECM won’t detect engine knock, risking engine damage. Always diagnose and repair the root cause first.

What’s the difference between P0327 and P0328?

P0327 is “Knock Sensor 1 Circuit Low Input,” meaning the signal voltage is too low. P0328 is “Knock Sensor 1 Circuit High Input,” meaning the voltage is too high. Both indicate a problem with the knock sensor circuit, but the causes and fixes may differ. A low signal often indicates a faulty sensor, while a high signal may suggest a short to power or wiring issue.

Will a bad knock sensor cause my engine to knock?

Not directly. A faulty knock sensor won’t cause knocking itself, but it prevents the ECM from detecting and responding to actual engine knock. If your engine is knocking due to low-octane fuel, carbon buildup, or timing issues, a bad knock sensor means the ECM can’t adjust ignition timing to prevent damage. This is why it’s important to fix the sensor promptly.

Can I drive with the check engine light on?

Technically yes, but it’s not recommended. The check engine light indicates a problem that should be diagnosed. Driving with the light on means you’re operating without the knock sensor’s protection, risking engine damage. Have the code read and the issue diagnosed as soon as possible. Most auto parts stores offer free code reading.

Is the knock sensor the same on both banks?

Usually, yes. Most vehicles use identical knock sensors on Bank 1 and Bank 2. However, always consult your service manual to confirm the correct part number for your specific vehicle. Using the wrong sensor could cause additional problems.