C0221 is an OBD-II code that shows up when you have a problem with the right front wheel speed sensor. The sensor is a small device that is attached to the wheel hub. It is also referred to as the ABS sensor.
It is responsible for monitoring the speed at which the wheel is moving and sending that information to the ECU. This allows the Anti-Lock Braking system to apply the right amount of brake fluid pressure when you step on your brakes. If you’re driving on a slippery surface, the car can slow down without locking up the wheels. This plays an important role in preventing it from skidding.
Diagnose and a Faulty ABS Speed Sensor
When the wheel speed sensor is disconnected, faulty, or struck by dirt and debris, one of the first systems to get affected is always the ABS system. You may also lose traction control on your vehicle since the sensor is also responsible for sending speed information to the traction control system. Below are some of the symptoms you may notice with a C0221 code.
Common C0221 Symptoms
- Anti-Lock Brake System (ABS) warning light
- Locking tires when you step on the brakes
- Traction Control Light is on
- Check Engine Light or Service Engine Soon Light
C0221 Possible Causes
- Faulty right front wheel speed sensor
- Open or shorted speed sensor harness
- Poor electrical connection in the sensor circuit
Diagnosing C0221 Code in Your Car
1. Check the Right Front Wheel Sensor
The first quick and easy thing to do when you get a C0221 code is to give the right front wheel speed sensor a visual inspection. You want to see if there are any cuts in the wires or any rot or rust in the connector.
When the vehicle is moving, the wire that connects to the sensor tends to bend. With time, it can develop an internal breakage that causes the speed sensor to stop working. The connector also tends to accumulate moisture, causing the terminals to corrode. You’ll need to check for any green or blue deposits both at the terminals and where the connector goes.
If both the connector and wiring look good, the next thing to do is to remove the right front wheel speed sensor and take a look at it. Be careful when removing the screws that secure it to the wheel hub. Sometimes, the sensor can get stuck and force you to drill it out. This can cause damage to the hub which will also need to be replaced.
If you found anything wrong with the sensor wiring and connector, the best thing to do is to replace both. Replacing the connector on its own won’t help to solve the problem in the long run. If you found that the sensor was damaged, you’ll need to replace it as well.
2. Test the Right Front Wheel Sensor
If you take a look at the speed sensor and notice that it looks fine, the next step is to test it using a multimeter. What the multimeter does it send power at a very low voltage on one side of the circuit, let it go through the sensor, and back through the other circuit.
Be sure to put the meter in the Ohms setting when testing the sensor. This setting is normally indicated by a horseshoe-like symbol. The multimeter will then give you a number that must be within a certain range. If you get a reading that says “OL”, that means there’s a break in the circuit.
If the reading you get is not within the recommended spec, then the sensor is bad. To find out what range your sensor should be in, you could test a good working sensor and see if the reading differs significantly with that of the bad sensor. Alternatively, you could do some research online depending on the type of vehicle you own.
The next step to take while still testing the right front wheel speed sensor is to repeat the process while rotating the right wheel. Here, you’ll put the multimeter in the Alternating Current – Voltage setting and spin the wheel. Check the spec on the meter as the wheel rotates. It should also be at a certain range.
You can look up the recommended reading for your vehicle online. Alternatively, you can test the other working sensors and see what they are putting out. If the difference is significant, you may have a bad wheel speed sensor. But, before you replace it, you’ll need to check the ABS sensor tone ring.
3. Check the ABS Sensor Tone Ring
The tone ring or reluctor ring is a toothed or notched ring that is located inside the wheel hub. It is what the sensor looks at then the wheel is spinning to determine the speed at which it’s moving.
If the hub has something wrong in it that causes too much play, the sensor will not be able to make a correct speed reading and this will cause a C0221 code. In some cases, something may have happened that caused the tone ring to break. You’ll need to raise the vehicle and check the wheel hub for excessive play.
All you need to do is place one arm at the top of the tire and the other at the bottom and push the wheel in and out. If you notice there’s too much play, that wheel hub will probably need to be replaced. The new hub should also come with a new wheel speed sensor that you can use to replace the old one.
4. Swap Your Wheel Sensors
Swapping your wheel sensors is a method that you can use if you do not have some of the test equipment mentioned in the steps above. Once done, drive your car and see if the code shifts. You want to look for a C0225 code which tells you that you have a problem with the left front wheel sensor. If this happens, you’ll be sure that the problem is with the sensor and that it will need to be replaced.
If you checked everything according to the explanation provided in this post and still couldn’t properly diagnose the problem, there could be a break in the wiring that goes to the ABS control module or you could have an issue with the module itself. You’ll need to check those out too to eliminate the C0221 code.
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