Common Chassis OBD II Trouble Codes & How to Fix Them - Part 1

Technical

Sep 14th, 2021

Common Chassis OBD II Trouble Codes & How to Fix Them - Part 1

OBD II codes fall into several different categories, depending on which subsystem of your vehicle is affected. 

Codes starting with a ‘C’ point to a problem with the chassis, covering issues beyond the passenger compartment. Typically, that includes problems with the brakes, power steering, and more.

In this guide, we’ll take a quick look at some of the most common Chassis (C) OBD II codes and what they mean.

About Chassis (C) OBD2 Diagnostic Trouble Codes

As you might already know, the diagnostic trouble codes displayed by your vehicle’s onboard diagnostics will start with one of several codes. Each code represents the car subsystem that’s affected by the issue.

For a quick refresher, check out our previous article introducing the basics of OBD2 and diagnostic trouble codes

Among those subsystem codes is C, which stands for ‘Chassis’. When a code starting with this alphabet appears, that means the problem is related to functions beyond the car’s passenger compartment. For example, there might be an issue with the steering, suspension, or even the brakes.

In the following section, we’ll explore a few common diagnostic trouble codes related to the chassis and give you tips on how to resolve them.

Common Chassis (C) OBD2 Diagnostic Trouble Codes

C0000 - Vehicle Speed Information Circuit

Affected part: When this code appears, it's a sign that your car's power steering function is facing issues. To be precise, the problem is related to the power steering control module or PSCM.

What is likely happening: There are several possibilities behind what’s triggering this code. First, the PSCM as a whole is likely faulty. Besides that, the PSCM could have an open or shorted harness, or it might be suffering from a poor electrical connection.

Symptoms: Your vehicle’s power steering function works differently depending on the car’s speed. When the car moves slowly, like in a parking lot, the power steering focuses on providing easy turning to help you park.

When driving fast, the power steering’s aim is to provide you with added stability.

How to fix the problem: This is not a typical DIY problem that you can solve at home. Instead, a qualified technician must diagnose your car’s power steering function, particularly the power steering control module and its various electrical connectors.

C0238 - Wheel Speed Mismatch

Affected part: The C0238 error code points to a wheel speed mismatch, which affects the front or rear speed sensors and possibly the electronic brake control module (EBCM). 

What is likely happening: When this code appears, the problem could be faulty speed sensors on the front or rear of your vehicle, or the harness connected to them is open or shorted. Another trigger for the same code is when the sensors suffer from a poor electrical connection.

Although somewhat less likely, it’s also possible that the electronic brake control module (EBCM) could also be faulty.

Symptoms: Typical symptoms that accompany this error code is the Check Engine or Anti-Lock Brake System (ABS) lights will turn on.

How to fix the problem: Fixing this problem will require a close diagnosis of the front and rear speed sensors, as well as the electronic brake control module (EBCM). Again, this task is best left to a qualified technician, primarily since it affects your brake system. 

C0300 - Rear Speed Sensor Malfunction and C0305 - Front Speed Sensor Malfunction

Affected part: These codes are a perfect demonstration of how OBD II codes are structured. Although the problem is similar, the diagnostic codes will be different depending on which part is affected. In this case, the problem is with the speed sensors at the front (C0305) or rear (C0300).

To be more precise, these codes refer to the front or rear prop shaft speed sensor, which is faulty.

What is likely happening: The front or rear prop shaft speed sensor is likely faulty. Besides that, their harness could be open or shorted, or a poor electrical connection might lead to these components.

Symptoms: Symptoms that might accompany these error codes include the Check Engine light turning on or the Anti-Lock Brake System (ABS) light doing the same. 

How to fix the problem: The affected sensor must be tested for any malfunctions to fix this problem. If necessary, the sensor will need to be replaced to gauge the speed of its prop shaft accurately. That way, the car will receive accurate data, and its systems can function correctly.

C1778 - Power Steering Failure

Affected part: The C1778 code appears when there’s a problem with the car’s power steering feature. Power steering has become an essential feature that drivers often overlook. So, as you might imagine, having this fault code appear is not a good sign, as it could affect your ability to drive comfortably.

What is likely happening: Typically, the trigger is a faulty power steering sensor. The sensor itself might have become faulty, or its harness is open, shorted, or receiving a weak electrical connection.

Symptoms: Some tell-tale signs of this problem include the Check Engine or Anti-Lock Brake System lights turning on. The ABS light is related to this because the ABS module monitors the power steering sensors. 

So, when the module senses that something is not right with the power steering sensors, the ABS light on the instrument panel will turn on.

How to fix the problem: Fixing this problem requires an up-close inspection of your car’s power steering system. To be more precise, the focus needs to be on the power steering sensors, as that’s the most likely trigger for this error code.

Assuming the sensors are working correctly, then the harness and electrical connectors must also be inspected.

To learn more about onboard diagnostics and error codes, stay tuned to the blog at Carpart.com.au. We'll continually explore the most common diagnostic trouble codes from each subsystem, from the chassis to everything else.


By Ray Hasbollah