C0129

The C0129 diagnostic trouble code means the chassis control module has identified a power steering position sensor circuit malfunction problem. This code indicates that a chassis sensor or its circuit is not providing expected readings to the ABS/stability control system. Accurate sensor data is essential for the proper operation of anti-lock brakes, traction control, and electronic stability control, and a fault in this circuit can cause these safety systems to be disabled. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Vehicle pulls to one side during braking. Speedometer reading erratically or showing zero. Unusual clicking or grinding noise from wheel area. Stability control (ESC/VSC) warning light on. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Damaged wheel bearing causing sensor misalignment. Faulty wheel speed sensor. Failed yaw rate or lateral accelerometer sensor. Corroded or broken sensor wiring/connector. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Connect an OBD-II scanner and read all stored chassis trouble codes and freeze frame data. Monitor wheel speed sensor signals using scan tool live data while driving. Inspect the affected sensor and its wiring connector for damage or corrosion. Check the sensor air gap and tone ring for damage, debris, or excessive wear. Test the sensor resistance and voltage output with a multimeter; compare to specifications. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Chassis (C) collection on OBD Codes. We provide comprehensive, up-to-date information to help you find solutions quickly.