The last thing any driver wants to see is a DTC that keeps returning despite fixing the car. In such a scenario, it means there’s an underlying problem you’re yet to address. So, what does it mean when the knock sensor code keeps coming back?
Often, problematic wiring sending unreliable signals could be to blame. If you experience a knock while driving, the knock sensor, spark plugs, or the ECU could be defective. The best way to resolve this troublesome code is to identify and address the underlying problem.
I provide the causes of the knock sensor code coming back and what you should do. You’ll also understand what a knock sensor is and what it does in your vehicle.
Answer: Knock Sensor Meaning
The knock sensor is one of the many sensors in modern combustion engines. It detects irregular engine vibrations or knocking noise and relays a signal to the ECM. This sensor is mounted on the engine block to ensure real-time detection of high-frequency vibrations during combustion.
The goal is to alert the onboard computer when abnormal vibrations occur to prevent or mitigate the engine knock.
Usually, abnormal vibrations will occur when the air-fuel mixture ignites prematurely. When the ECM receives the sensor’s signal, it adjusts ignition timing or fuel delivery to resolve the problem. The ECM springs into action to optimize performance and prevent engine damage.
Your vehicle’s check engine light will illuminate if the vibrations or engine knocks persist. Then, the ECM will register a knock sensor fault code. You might also notice other symptoms like:
- Engine misfires
- Decreased fuel efficiency
- Knocking or pinging sound
- Loss of power
- Engine fails to start
Such symptoms will let you know your engine requires immediate attention.
Question: Why the Knock Sensor Code Keeps Coming Back
If you fix the underlying problem, the knock sensor code and check engine light should disappear. However, if the code keeps returning, it means there’s a critical issue you must address.
Remember, clearing the code with your diagnostic tool will not help. The best thing is to understand the code and diagnose the problem. You’ll likely deal with one of the following trouble codes related to the knock sensor:
- P0325: It indicates a malfunctioning knock sensor circuit.
- P0326: Knock sensor circuit’s range or performance is out of range or weak.
- P0327: It indicates a knock sensor circuit’s low input signal.
- P0328: Knock sensor circuit’s high input signal.
- P0330: It indicates a malfunctioning knock sensor 2 circuit.
If these codes keep reappearing, the root cause could be the following:
Malfunctioning Knock Sensor
Damaging the sensor during replacement or installing a bad sensor can result in the knock code returning. Again, incorrect installation can cause the sensor to malfunction. The sensor might not detect engine knocks or relay inaccurate readings.
To address these issues, inspect the knock sensor to see if it’s properly installed. If not, install it to the manufacturer-recommended specifications.
You’ll need to install a new knock sensor if you’re dealing with a damaged/faulty sensor. Handle the new knock sensor carefully to avoid damaging it.
Note: After replacing the knock sensor, reset the ECU (Engine Control Unit). Doing so ensures your ECU adapts to the sensor’s readings. After resetting the car computer, perform an idle relearn procedure and clear stored codes to ensure the new sensor sends accurate data.
Faulty Wiring or Connections
Broken or frayed wiring can cause the code to keep occurring. Still, loose, corroded, or damaged connections will trigger this problem.
The wiring and connections transmit signals to the ECU. So, if they’re faulty, they might fail to send the signal.
When fixing wiring or connection issues, use a multimeter to test continuity. You can also check for physical damages and replace broken or frayed wires. Secure loose connections and clean them with a specialty contact cleaner to remove accumulated rust.
Bad Spark Plug
A defective spark plug won’t provide the required spark to ignite the air-fuel mixture. As a result, there’ll be an incomplete combustion, leading to abnormal engine vibrations. Then, the knock sensor will detect this issue and communicate with the ECU.
If the ECU interprets the signal as an engine knock, it’ll keep triggering the knock sensor code. Replacing a defective spark plug or cleaning it can help fix this issue. You’ll also need to check if the plug is loose and secure it properly.
Bad Gas
If the knock sensor code keeps coming back, check if low-quality or bad gas is to blame. Poor-quality or old gas can cause incomplete combustion, leading to the engine knocking. The ECU will learn about this issue with the help of the knock sensor and trigger a fault code.
Check the fuel quality to see if it’s old or contaminated. If so, replace it with high-quality gas with a higher octane rating and recommended additives.
Inadequate Engine Oil
Engine oil allows proper lubrication to prevent friction and heat on the engine’s moving parts. If there’s insufficient oil or low oil pressure, parts in the engine will overheat due to lubrication problems. As a result, your engine will experience abnormal vibrations and knocking.
When the knock sensor detects these vibrations, it’ll trigger the fault code. Maintaining a proper oil level will help resolve this issue. So, refill the reservoir if the oil level is low. You can also change the oil if it looks old or contaminated.
Faulty ECU
Like other electronic components in your car, the ECU can malfunction over time. It might fail to interpret sensor readings and record false codes. In this case, the car computer will trigger several codes, including the knock sensor DTC.
If you fail to fix the ECU, these codes will keep reappearing. Typically, the ECU fails due to old age, electrical problems, or software issues. A professional mechanic can diagnose and resolve problems related to the ECU.
Question: Can You Drive With a Malfunctioning Knock Sensor?
A malfunctioning knock sensor doesn’t make your car inoperable. However, this sensor plays a significant role in safeguarding your engine from potential damage. If you drive with a defective knock sensor, you’ll experience engine knock, decreased fuel efficiency, and reduced engine performance.
With time, the engine knock will cause irreparable damage to the engine pistons, bearings, connecting rods, and other components.
If you’ve examined your vehicle and tried fixing all the above, but nothing works, consider seeking help from a professional. A mechanic or dealership will use specialized diagnostic tools to diagnose and fix the root cause.
Final Thoughts
You now know why the knock sensor code keeps coming back. Check if a faulty knock sensor, bad wiring/connections, defective spark plugs, a malfunctioning ECU, or low-quality gas is to blame. Address these issues to prevent the knock sensor code from reappearing.
If the code returns, seek assistance from an experienced mechanic or the dealership. Lastly, regular checks and maintenance can help increase the knock sensor’s longevity and boost your engine’s performance.