All modern cars today rely heavily on sensors. Sensors help the car run smoothly and efficiently. These sensors are crucial to the safety of cars. One sensor is called the knock sensor.
You might have recently bought a used car and noticed that at times it jerks, vibrates, pulsates, or make any other weird noises. That is because you may have a malfunctioning knock sensor.
You don’t have to worry anymore though because in this article we are going to answer the question “Can you drive with bad a bad knock sensor?”.
1. What exactly does a knock sensor do?
First, let’s take a closer look at the knock sensor. Knock sensors are located on the outside of the engine block, at a position where they can detect knock. The number of knock sensors depends on your car’s engine.
There is one knock sensor on inline 4/5/6 cylinder engines, whereas V6, V8, and V10 engines have two knock sensors.
A knocking sound is produced when there is an unplanned ignition in your engine. Basically, knock sensors detect knocks from the engine block and transmit them as electronic signals to the ECU.
According to the Clemson University Vehicular Electronics Laboratory (CVEL), There are two approaches used to sense engine knock – vibration detection and pressure measurement. Most knock sensors operate based on the first method.
The ECU then uses this information to adjust ignition timing and fuel mixture (to reduce knocking), as well as optimize performance by starting ignition as early as possible or increasing torque/power output.
2. Can you drive with bad knock sensor?
Yes, a car with a bad knock sensor is still drivable. However, it can negatively impact the engine’s performance and fuel economy since the ECU won’t be able to detect engine knocks.
Aside from poor engine performance, spark-plug points may overheat and the combustion chamber surface may become eroded.
As mentioned above, if you continue to drive with a bad knock sensor, you may be damaging your engine. We strongly recommend having them replaced immediately.
It will be cheaper as compared to compromised fuel economy and long-term engine damage. Knock sensor replacements generally cost from $65 to $190.
Related: Can You Drive with a Bad O2 Sensor? Read These 8 Facts
3. How long can you drive on a bad knock sensor?
Most cars’ engine today has two knock sensors and if one goes out, you can still drive for a few hundred miles without even noticing it. It won’t affect your vehicle’s performance at all, as long as the other one doesn’t go out too soon.
However, once both knock sensors fail, you will start noticing bad acceleration and a rough engine idle. When this happens, we strongly suggest addressing the problem immediately.
Related: How Long Can You Drive a Car With a Bad Speed Sensor?
4. Symptoms of a bad knock sensor
When your knock sensor is bad, you may notice a few different symptoms. These include:
- A lack of acceleration when the engine reaches 2,500 RPM
- The engine light is on because of the knock sensor going out
- Smooth or rough idle (depending on how damaged the knock sensor is)
- Pinging noise from the engine
- Strong exhaust and burning smell due to the detonation in the cylinders
- Poor fuel economy
5. Can a bad knock sensor damage the engine?
Yes, aside from affected engine performance and fuel economy, a bad knock sensor can damage the engine if ignored. If your car has a faulty knock sensor, it can damage the engine.
A knock sensor is there to detect detonation or spark knock. This means that if your car’s engine is running too hot, a bad knock sensor will not be able to accurately detect detonation and will allow it to run much hotter than normal. The heat from this can cause serious damage to your pistons and valves.
6. Can knock sensor affect transmission?
The short answer is no, but it feels like it does because the detonating / knocking/pinging equates to performance loss. The knock sensor will affect the ignition timing and power accordingly, but the transmission will still move.
The knock sensor is a device that detects engine knock or detonation in an internal combustion engine. If it detects excessive levels of these vibrations, it sends a signal to retard ignition timing.
This reduces the tendency for pre-ignition or detonation which otherwise causes engine damage due to overheating.
7. How do you check for a bad knock sensor?
You can check using a multimeter or an OBD II scanner. Before removing a knock sensor, ensure that the ignition is turned off.
- Check the resistance using a multimeter
- The resistance should be between 2,00 and 3,000 ohm. If it’s not, the knock sensor is probably faulty
- If there is a correct resistance, proceed by checking the electrical connectors. If there is no voltage, check all wirings and look for any signs of damage to the circuit
- Finally, check the torque at which the knock sensor has been fastened. Make sure that it is not fastened too much so it can operate properly.
The most accurate way to identify a bad knock sensor is through an OBDII scanner. A bad sensor will throw a code that will identify the problem. We highly recommend the INNOVA 6030P OBD2 Scanner. It is an affordable scanner that can assist you with most check engine light problems including bad O2 sensors.
With INNOVA 6030P you can diagnose your car’s O2 sensors directly, you can also see key information about your vehicle in real-time to aid in diagnosis.
Here are some of the common fault codes related to bad knock sensors:
- P0325 Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
- P0326 Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)
- P0327 Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)
- P0328 Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
- P0329 Knock Sensor 1 Circuit Intermittent (Bank 1 or Single Sensor)
- P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)
- P0331 Knock Sensor 2 Circuit Range/Performance (Bank 2)
- P0332 Knock Sensor 2 Circuit Low Input (Bank 2)
- P0333 Knock Sensor 2 Circuit High Input (Bank 2)
- P0334 Knock Sensor 2 Circuit Intermittent (Bank 2)
Related: How To Tell Which ABS Sensor Is Bad: 2 Simple DIY Methods
This article answered the question “Can you drive with bad knock sensor?”. Yes, you can drive with a bad knock sensor, but the engine’s performance will be greatly affected.
If your vehicle has been running for several days on a bad knock sensor, then it should be replaced immediately before it causes any further damage to your engine or transmission.
A faulty knock sensor can cause serious damage to any number of internal parts in an engine, which could lead to expensive repairs later down the road.