Ask The Mechanic: ABS brakes, air bag and tire pressure monitor

ABS brakes, air bags and tire pressure monitors are common safety-related items found on most cars and mandatory on all new vehicles that we see on the road today.

I was asked what these items are for and why I need to repair them if they fail.

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ABS, which stands for anti-lock braking system, was primarily designed to maintain a better level of steering control in low traction driving conditions. As long as a wheel is rotating, the driver maintains some control of the steering direction. If the wheels are locked up and sliding, it is like the old saying: “Now the tail is waging the dog.”

There is absolutely no control and the vehicle is victim to what the road surface has to offer, which is sometimes pure ice, which is great for skates, but not rubber tires.

When ever a vehicle starts up it does its own self check to confirm system integrity. If a fault occurs it will turn on the ABS warning light, disable the ABS functions and the vehicle resorts back to normal non ABS operation. As long as the brake pedal is firm you should have regular brakes.

(One other note: ABS brakes don’t operate below 12 km/hr and, if your tires are tread-bare, the ABS may not be able to work.)

Airbags were never mandatory in Canada because more than 90 per cent of Canadians wear their seatbelts. It is the seatbelt the saves lives. The airbag is classified as a supplemental restrain system, which only adds a little extra level of protection. Since most of our vehicles are made for the U.S. market and the use of seatbelts there was at less than 50 per cent, airbags were introduced to North American for compliance and safety reasons.

Airbags and seatbelts on some vehicles work in tandem with each other. When the system is activated, because of an impact, the seatbelt has a small charged device that will pull you back against the seat before the airbag is activated. That way, your body is not twisted, which could result in improper airbag deployment.

(Because of certification requirements, mixing of a Canadian market vehicle’s airbag is incorrect and vice versa with its U.S. counterpart.)

The tire-pressure monitoring system (TPMS) is an electronic system designed to monitor the air pressure inside the pneumatic tires on various types of vehicles. A TPMS reports real-time tire-pressure information to the driver of the vehicle, either via a gauge, a pictogram display or a simple low-pressure warning light.

Nor was this system mandatory in Canada, but since it is installed on vehicles, it does have to work as certified by Transport Canada. In the U.S., TPMS was legislated under the Tread Act to minimize the frequency of tire-related issues due to under-inflation. It had become quite a concern that required government involvement to resolve.

For any concerns or questions, email me at

Gary MIller is a retired service advisor.

© Kamloops This Week



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