QUESTION

Hi John,

I hope you can help. The VSA indicater light on my (wide bodied) Honda Accord instrument panel is on constantly. A Honda dealer did the normal "diagnostic " check and quoted $1300 for a new yaw sensor. I rang a wrecking yard and was told they had the right model and the sensor would cost me $200 - except they couldn't find where it was.

I was told it is under the drivers seat or under the transmission hump or in the ashtray - no joy.

Can you help please?

Ray

ANSWER

Hi Ray,

FYI - yaw is the rotational movement of the car about a vertical axis, kinda like the way an old record player spins the vinyl. When a car goes around a bend it does two things:

It changes direction
It yaws

If you think about a car turning from one street into another - for example from going due north to due east - the car needs to change direction from north to east, but it also needs to rotate 90 degrees to the right (clockwise, when viewed from above). The 90 degrees clockwise rotation is an example of yaw.

VSA is Honda's trade name for stability control - the computerised system designed to prevent skids and slides. It keeps cars pointed in the right direction in situations where commonly they would have lost control before that technology was available.

Stability control compares a range of inputs - mainly speed, steering angle and yaw. The computer knows how much steering input is required for a particular amount of yaw response from the body at every particular speed. So, if the driver is turning the wheel too much at a particular speed, and the body is yawing too little, the computer deduces the car is running wide (understeering). If the yaw is too great for the steering input, the computer deduces that the tail is overtaking the nose (oversteering). In either case it knocks back engine power and has the capacity to brake individual wheels to get the right amount of yaw response and get the car back on track.

The dealership's diagnosis makes sense. If the yaw sensor is defective the VSA system will go nuts. Like, Houston, we've got a problem.

The yaw sensor on the eighth-generation Honda Accord is under the centre console, between the seats - basically somewhere under your left elbow when you're driving the vehicle. It's inside the cabin, not under the floor. This makes sense because this is near the vertical axis of the car, which it's likely to rotate about when it yaws during directional change. (It's where an engineer would put the thing if the world were ideal.) I know yours is probably the last of the seventh-generation models, but the principle and the location are likely to be very similar. I couldn't locate the seventh-gen manual or information. But since it's pretty easy to remove the console, you should just take a look after pulling it out. It appears that Honda labels the sensor with its function, so it should be easy to identify.

Below are some service manual instructions for replacing the sensor - take note of the warnings about dropping the sensor or using power tools to fit it - be gentle. And get a guarantee from the wrecker that the sensor is functional - because if it has been dropped or mistreated in the removal/storage process it might be cactus, and nobody will know.

The instructions are for the North American version of the car. (Here's their blurb: "The North American version of the Accord has a different body from its Japanese counterpart. This shape is sold as the Honda Inspire in Japan, and is not sold in Europe. It was discontinued in Japan in September 2012. Larger than the previous model, the sedan is now classified as a full-size car by EPA standards. A coupe version is available, as well as a Crosstour fastback model, which was introduced in the US for the 2010 model year.")

You can review these yaw sensor replacement instructions online.

You can access the Honda Accord eight-generation service manual (North America). There will probably be minor differences between that LHD car and our RHD one. There might also be minor differences between the sensor in this one and your one.

You will need to get the Honda dealer's computer plugged in again to initialise the new sensor.

Please let me know how the fix goes in the contents section below.

Best of luck with the replacement.

Thanks for listening on 2UE.

Sincerely,

JC

How Do I Replace My Yaw Sensor?

QUESTION

ANSWER