All trouble codes are serious business. Some mean expensive repairs and months on the lift, but not all check engine light codes are equal. The C0221 is a less serious code, but a trouble code nonetheless. It’s a fairly common one too, so don’t be surprised if you run into it.
Fortunately, you don’t have to be a certified tech to diagnose and repair this code, which usually indicates a wheel speed sensor issue.
In this guide, we’ll show how to do both those things and go through the symptoms and causes as well as anything else you could need to sort out this issue.
What is the C0221 Code, and What Does It Mean?
The C0221 is an ABS sensor code. The ABS or Anti-Lock Braking system prevents your wheels from locking up in the event of heavy braking. This is especially important in emergencies as it allows you as the driver to steer and avoid obstacles while braking hard.
However, for the ABS system to work as intended, it needs to know how fast the wheels are spinning. The way the ECU gets this data is through a wheel speed sensor. When this sensor decides to kick the bucket, you’ll run into
Where is the Wheel Speed Sensor Located?
A 4-wheel ABS uses ABS wheel speed sensors on each wheel to detect when traction is being lost. The C0221 code means that the right front wheel sensor is malfunctioning, so in this case, you should be looking at your front right wheel hub.
Some vehicles use a 2-wheel sensor system, placing sensors on both the front wheels. Consult your owner’s manual to see which type of sensor you have.
The sensor is usually located on the top of the hub on many vehicles. If you look closely, chances are that you’ll find a wire that runs from the top of the hub along the suspension. That’s your wheel speed sensor line.
The location of the wheel speed sensor exposes it to many issues. Not only is it exposed to the elements and prone to physical damage, the wire harness for the sensor itself is constantly bending as you turn the wheels.
Given enough time, all of these things can create an issue with the sensor itself, or the wiring. That being said, there are instances where you’ll get the CEL and ABS light with this code, but your sensor will be perfectly fine. Because of that, it’s a good idea to approach this issue with an open mind and take a few more things into consideration before you pull out the parts cannon. Here are a few causes of the C0221 that you should be aware of:
- Right front wheel speed sensor failure
- Faulty speed sensor harness
- Battery-Related issues
Right Front Wheel Speed Sensor Failure
The C0221 code is most commonly caused by the wheel sensor failing, either due to mechanical damage or corrosion. The sensor’s exposure to the elements causes the rubber and other materials to harden, become brittle, thus increasing its chances of failure. Unfortunately, due to its design, it’s not a matter of if the sensor will fail, but when.
Faulty Speed Sensor Harness
The sensor wiring harness is exposed to the same elements and experiences the same issues that the sensor does. Moisture corrodes the connector between the sensor and the wiring harness. Although it’s less common, the rubber insulation of the harness can crack and eventually cause the wires themselves to break.
Battery-Related Issues
Every sensor uses electricity to send information to the PCM. Battery cells usually fail progressively causing the voltage output to drop. Once the battery is no longer capable of delivering the necessary power to main and auxiliary systems in your car, you’ll start experiencing a wide range of issues, including the C0221 code. A blown fuse or relay can also cause your ABS light to pop up with the C0221 code.
Bad Sensor Calibration
Bad sensor calibration doesn’t cause a C0221 code. However, it will cause your ABS light to illuminate when the car is driving straight, and you can misconstrue that as a speed sensor issue.
This is especially true if you’re working without an OBD II reader. Fortunately, there’s an easy way to reset your ABS system and eliminate sensor calibration as a potential cause of the ABS light. This procedure works on many makes and models, but keep in mind that it may not work in yours. There’s no real substitute for an OBD II scanner when it comes to clearing fault codes. Anyway, the procedure is as follows:
- Turn the key to the on position but don’t start your engine
- Press your accelerator pedal 3 times in rapid succession
- Start the car
The ABS light should clear right away, or after a very short drive. Either way, this procedure dumps all the data stored in the ABS/DSC module, returning everything to default settings.
What Are the Common Symptoms of C0221 Fault Code?
Being a fairly simple error, there are only a few symptoms that you can expect to encounter, and most of them have to do with your ABS.
- Warning lights
- Wheel locking under heavy braking
- Premature Brake pad wear
Warning Lights
In most cases, when your vehicle has an issue, the check engine light illuminates. Your ABS has a specific light that turns on when the vehicle loses traction. When you have C0221, the ABS or TC (traction control) light may stay on permanently.
This is mainly because of how the powertrain control module reads signals from the sensor. When the car loses traction and the brake pressure needs to be modulated, the sensor will signal as open and the ABS light will turn on.
Wheel Locking Under Heavy Braking
As the ABS is responsible for preventing the wheels from locking under heavy braking, it makes sense that a sensor failure will prevent the system from functioning properly. The ABS may deactivate or not modulate the right front wheel’s brake pressure correctly.
Premature Brake Pad Wear
The ABS modulates brake pressure to prevent traction loss under heavy braking. If it is doing this at low speeds or when you don’t need it, it can lead to premature brake pad wear on the affected wheel.
Now, there are a few other issues such as warped rotors or caliper pins, that can cause premature wear. So much so that most people completely overlook their ABS system when dealing with premature brake pad wear. Good brake system maintenance habits can prevent much of this confusion as you’ll always know what’s going on with your brakes.
How to Diagnose the Cause of C0221 Code
Diagnosing a speed sensor issue is easy. You don’t need any special tools to access or replace it, nor do you need a significant amount of technical skill. You just need to jack up your vehicle, remove the right front wheel, and you can begin testing.
Visual Check
The first step is to check the sensor for mechanical damage. This is fairly common and the main reason these sensors fail. If it’s loose, the contacts are corroded or there is any major damage to the sensor, look at sourcing a replacement.
When removing the sensor, avoid using a large amount of force. The screws that fasten the sensor to the wheel hub are usually corroded. Going ham on them will usually snap them or round the bolt. If the bolt is giving you a hard time, soak it in penetrating oil and leave it to sit for a while. That will greatly improve your chances of getting the bolt out in one piece.
The wiring harness is similarly a weak point. Check for any breaks, cracks, or exposed wires in the harness or connector. The absence of any external damage does not mean there is not an internal short. However, it’s much less likely that you will have such an issue with no damage to the rubber coating.
Iron brake dust oxidizes when exposed to air, which causes the outside of the brake rotor to be caked in rust. Sometimes, when conducting a service or driving, specks of rust can break off and become lodged in the sensor.
ODB II Reader
Of course, once you’ve ascertained there is an issue with your ABS, you can dive right in and check every wheel sensor. However, the ODB II reader allows you to detect exactly which sensor has a problem. Each sensor has a different failure code. Run a full scan and look at all the codes to assess what’s going on.
Multimeter
A multimeter is a golden tool for testing anything electrical. Here, you can use it to test all the parts related to the C0221 trouble code.
Your owner’s manual has a great deal of information on the resistance (ohms) range that the sensor should operate in. This differs between vehicle manufacturers, but the technical data for your specific sensor is correspondingly widely available on the internet.
You can test the wiring harness by back probing the connector with your multimeter. Turn the vehicle on and identify the wires. There are three wires; ground, signal and live. In most cases, the red wire is positive, the brown wire is the ground wire and the signal wire is black.
Now that you’ve identified the wires, you need to touch the positive (red) multimeter probe to where the signal wire enters the connector. You may need to peel back some of the insulation to access it. Use your black probe to find a ground on your vehicle, which in this case is any metal part of the vehicle’s chassis.
Most sensors output 5V on the signal wire, so you should get around that figure. The positive wire should give you around 12V.
How Do You Test a Faulty Wheel Speed Sensor Without a Multimeter?
One of the least technical ways of testing whether your wheel speed sensor has failed is by swapping the sensors around. You can then use your ODB II reader to check whether the code moves. Each sensor has a different trouble code.
You can similarly look at the individual reading of the sensor on the ODB II reader. The sensor reads as open when the vehicle loses traction, so if there is an issue, it will read as open when the vehicle is not moving.
Fixing a C0221 Code
Fixing this trouble code is as simple as replacing the sensor or wiring harness, as those are the two key problems related to the trouble code. Fortunately, the wiring harness and the sensor itself come together in the box. One thing to remember is the sensor has to be calibrated before driving your vehicle. Additionally, the brake rotor should be cleaned, and any rust removed when doing this job.
Swapping out your battery for a fresh one, or replacing the fuse, can correspondingly solve the issue, so if all else fails, just go for that option.
Does C0221 Clear Itself?
The easiest way to clear a C0221 is by using an ODB II reader. If you don’t have access to one, the code will clear itself as soon as the PCM registers contact with the sensor. Taking a long, pleasant drive will usually allow the code to clear as well.
Can You Drive with C0221 Code?
Yes, you can drive with a C0221 code. The ABS is a safety feature meant to aid you in emergencies. In saying that, It is not something you would want to ignore for long. Most vehicles allow you to drive with this trouble code, but some may put your vehicle into limp mode, in which case you won’t be able to drive.
Get Quality Parts for Your Car
Getting a quality right front wheel sensor is essential if you want to prevent the C0221 error from coming back. Your ABS is an essential safety system, and is definitely not something you want to repair with cheapo parts. Your life may very well depend on you using quality spares.
This is why we stock all ABS sensors and anything else you might need for your vehicle. Our easy-to-use website, eEuroparts.com, gives you access to parts tailored to your vehicle. All you have to do choose your vehicle from the dropdown list and search for the parts you need. The results will only include products that are a guaranteed fit for your car.
