Diagnostic trouble codes offer plenty of information when you’re trying to diagnose your car’s problems. Unfortunately, they can be quite challenging to interpret, especially since there are so many different codes.
We’re continuing our ongoing series on some of the most common OBD II trouble codes in this guide, particularly those in the Chassis (C) category.
Recap: Chassis (C) OBD2 Diagnostic Trouble Codes
As mentioned earlier, this guide is the second instalment of an ongoing series covering the most common OBD II trouble codes, particularly those in the Chassis (C) code subsystem. If you can’t find what you’re looking for here, be sure to check Part I of the series, where we cover codes C0000, C0238, C0300, and C1778.
To recap, Chassis (C) codes are those related to issues outside of the passenger cabin. These codes point out problems regarding the following:
- Steering system
- Suspension system
- Braking system
- And more
Besides Chassis (C) codes, the other categories of OBD II trouble codes are:
- Body (B)
- Powertrain (P)
- User Network (U)
Don’t worry if you can’t remember or don’t understand how these codes work because you’ll get everything you need from our introductory article on OBD2 codes here.
For now, let’s look at another batch of common OBD2 diagnostic trouble codes, particularly from the Chassis (C) code subsystem.
Common Chassis (C) OBD2 Diagnostic Trouble Codes
C001E - Right Rear Hydraulic Release Is Too Long
Affected part: This code is focused mainly on the hydraulic release valve located on the right rear side. If you see codes that are very close to this one, you’re likely experiencing a problem with the same part on other sides of the vehicle.
What is likely happening: Three possibilities can trigger this code. First, it could be a malfunctioning hydraulic release valve on the right rear side.
If that part has no problem, the issue could be with the valve’s wire harness and suffers from a poor overall connection.
Symptoms: This part of your car falls under the Anti-Lock Brake System (ABS). So, when there’s a problem, you’ll likely see the ABS warning light turn on, along with the Check Engine or Service Engine light (depending on which one your car has).
How to fix the problem: The repair for this code involves an inspection of the rear right hydraulic release. If that component is in good shape, then the wire harness and other electrical connections require troubleshooting.
C0020 - Anti-Lock Brake System (ABS) Pump Motor Control Issue
Affected part: As the name suggests, this code relates to your vehicle’s Anti-Lock Brake System (ABS) and its control module. However, a problem with the Hydraulic Control Unit (HCU) can also trigger this code.
What is likely happening: The most likely problems here are faults with the components themselves (i.e., the ABS or HCU mentioned above). If those parts are working as they should, the problem is with their wiring, which could be damaged or shorted out.
Symptoms: This error happens alongside an illuminated ABS warning light. On some vehicles, you’ll also see the Check Engine light or its equivalent (e.g., Service Engine Soon light) turned on.
How to fix the problem: You should first inspect the electrical connections on these components. If they’re okay, then you’ll have to replace the affected part, whether it’s the ABS control module or the Hydraulic Control Unit (HCU).
C0021 - Brake Booster Performance Problems
Affected part: This error code is primarily associated with the brake booster, which magnifies the force you apply on the brake pedal against the master cylinder.
Although less likely, the same code can also represent a problem with the Vacuum Pressure Sensor.
What is likely happening: This code signals that the brake booster or vacuum pressure sensor are not working correctly.
Besides that, it’s also possible that the electrical wiring for these components is damaged.
Symptoms: This error code appears in conjunction with the ABS warning light and Check Engine Light turning on.
How to fix the problem: Troubleshooting this problem should always begin with the cheapest parts to replace. In this case, that means inspecting the wiring to ensure that they’re free from damage. Plus, the electrical connectors should be pushed firmly into place if they are loose.
Once the connections have been ruled out as the cause, the brake booster and vacuum pressure sensor must be checked for faults. Whichever of those two parts has failed must be replaced.
C0023 - Erratic Signal from Front-Right Wheel Speed Sensor
Affected part: This code is triggered when your car doesn’t receive a clear signal from the wheel speed sensor on the front right side. If you see a code close to this one, you’re likely experiencing the same issue on another one of the wheel speed sensors.
What is likely happening: When the wheel speed sensor fails to send a clear signal to the car, it means the sensor or its wiring is damaged. A short circuit or other electrical faults can also trigger the same code at this part of the car.
Symptoms: Like the other components mentioned in this guide, the Anti-Lock Brake System (ABS) module monitors the wheel speed sensor. Because of that, you’ll likely see the ABS warning light turn on when this problem happens.
How to fix the problem: As usual, the troubleshooting process begins by inspecting the wiring and connectors. If the wiring is free from damage and the pins on the connectors are in good shape, the problem is likely with the wheel speed sensor itself.
If necessary, the sensor must be replaced with a new one.
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