ABS + TCS

Question 1

What is the purpose of the anti lock braking system?

Answer 1

Designed to ensure driver can maintain control in an emergency when brakes lock

Question 2

What is the effect of pedal pressure too high?

Answer 2

One or more wheels will skid increasing stoping distance and jeopardise directional control

Question 3

What is the result of pedal pressure too low?

Answer 3

Stopping distance will increase

Question 4

What are the 3 stages of cadence breaking?

Answer 4

Pressure maintenance

Pressure decrease

Pressure increase

Question 5

What happens to the ABS under normal conditions?

Answer 5

Brake pressure will not be influenced until wheel lock situation

Question 6

Two sub-systems of ABS

Answer 6

Hydraulic

Electronic

Question 7

What is the ECU purpose?

Answer 7

Revives signals from sensors

Determines when wheel is about to skid

Question 8

What is the modulator?

Answer 8

Contains hydraulic fluid and modulating valves

Responds to signals from ECU to vary braking pressure

Question 9

What is the electromagnetic sensors?

Answer 9

Fitted to each whee station

Detects rotational speed by counting the teeth

Question 10

The ECU monitors how many sensor signals per second?

Answer 10

8000

Question 11

If a problem arises with the ABS what happens?

Answer 11

Light will illuminate on board computer

Question 12

What is the operation of the ABS under normal conditions?

Answer 12

Pedal is pressed

Shuttle valve is moved to allow hydraulic pressure

It also triggers the valve switch and this informs the ECU that the pedal is pressed

Pressure is then fed to the brakes

Inlet valve Is in the open and outlet valve are closed

Question 13

What occurs when wheel locks?

Answer 13

The ECU detects the speed

Inlet valve will close and outlet will remain close

Called pressure maintenance

Question 14

What happens when the wheel is still locking?

Answer 14

The outlet valve will be opened and pump activated

Draws pressure away

Pressure decrease

Question 15

What happens when the ABS recognises that they’re rotating at the same speed?

Answer 15

Full brake pressure is applied through the inlet valve to brakes

This is called pressure increase

Question 16

What happens in the solenoid valve under normal braking conditions?

Answer 16

Solenoid valve closed

Hold valve and exhaust valve open

Air flows straight to brakes

Question 17

What happens when pressure is held?

Answer 17

ECU energises solenoid valve

Air acts on diaphragm above hold valve

This closes the valve

Question 18

What happens when pressure is reduced?

Answer 18

Solenoid valve is energised and open

Air bleeds through solenoid and opens exhaust valve

This allows air to flow past the valve and to the atmosphere

Question 19

What is the need for traction control?

Answer 19

When the whee spins over a slippery patch , it will slow the wheel down to stay at the same speed as the others

Question 20

What Are the benefits of TCS?

Answer 20

Improved safety- driver maintains control

Reduced tyre wear- less likely to spin

Question 21

What are the 3 main components of the TCS?

Answer 21

Traction control solenoid valve

Traction boost unit

Pump