Rick's Free Auto Repair Advice

Traction light on and cruise doesn’t work

Diagnose and fix traction light on and cruise doesn’t work

When you get a condition like this: Traction light on and cruise doesn’t traction control iconwork, you’ve usually got a problem with a sensor. Before you start throwing any parts at the problem, start by pulling the trouble codes, and not with some cheap code reader. Many of the codes that can disable traction control and prevent cruise operation are P1000-series and P2000 series codes that can’t be read by a cheap scan tool. The problem can also be a communications “U” or body “B” code. So, like any other check engine light, start with the codes.

What are the parts of a traction control and stability control system?

Early traction control systems just worked in tandem with the anti-lock braking system. When the system detected one wheel locking up of one wheel spinning faster than the others, the system would brake the vehicle. But late model systems are much more complicated and include not only traction control, but also stability control. Here’s what’s involved.

Steering angle sensor—This tells the system what your steering intentions are.

Based on the steering wheel angle, the system compares that reading to the actual direction of the vehicle as shown by the yaw rate and lateral acceleration sensors.

Yaw rate sensor—detects variation around the vertical axis of the vehicle. Stick a pin into the roof of the car and yaw is the amount or rotation around the pin.

Lateral acceleration— sensor detects sideways movement of the vehicle.

Wheel speed— sensors report the RPMs of each wheel.

How traction and stability control work

The traction/stability computers monitor inputs from

all the sensor listed above. If the system detects the vehicle going in a different direction (yaw or lateral acceleration) than indicated by the steering wheel angle sensor, it will cut engine power, apply individual brakes to try and bring the vehicle back to the intended direction. It will also immediately disable the cruise control system.

How to diagnose

Once you have the trouble codes, you can conduct tests on the individual sensors.
The steering angle sensor and the wheel speed sensors are the most common failure points because they have mechanical components, while the yaw and lateral acceleration sensors use electronic gyro and acceleration technology.

Posted on by Rick Muscoplat

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