Page 158 - Foton Workshop Manual - Auman EST-M

DI - 104 Diagnosis - Diagnosis-fault diagnosis of electronic and electrical parts

Introduction of system function
1. Diagram of ABS control structure

Power Circuit
Gas circuit
Left front wheel
speed sensor
Left front wheel (intake Left front brake
and exhaust) solenoid
Right front wheel valve air chamber
speed sensor
Right front wheel (intake Right front brake
and exhaust) solenoid
Left rear wheel valve air chamber
speed sensor
Left rear wheel (intake Left rear brake
and exhaust) solenoid
Right rear wheel valve air chamber
speed sensor
Right rear wheel (intake Right rear brake
and exhaust) solenoid
Combination instrument valve air chamber
(air pressure signal of
brake system)
ABS failure
K line alarming lamp
Diagnostic unit (ABS state Combination
signal) instrument

2. Introduction of system function

a. ABS control
Based on the normal brake system, ABS system of this vehicle adds one ABSECU, four wheel speed sensors,
four solenoid valves and one indicate lamp for combination instrument, thus it can make the vehicle realize its
anti-lock braking function in case of high-speed driving or emergency stopping while driving on the ice-snow
road. ABS can make the vehicle maintain its steering stability and also reduce its braking distance greatly in
case of braking.

When the vehicle drives (at over 7km/h speed), the wheel speed sensor can monitor the wheel speed at any
time and send it to ABSECU. When the wheel speed sensor monitors that the wheel speed tends to 0 (wheel
lockup) in case of emergency stopping, ABSECU will control ABS solenoid valve to emit the air properly, and
reduce the frictional force between the brake hub and brake shoe to make the wheel speed properly increased.
When the wheel speed is too quickly increased, ABSECU will control the solenoid valve to stop air emission,
and increase the braking force to make the wheel speed reduced. The slip rate of wheel (the frictional force
of wheel is reduced, its slip rate is 100%, the vehicle is easy to runout or drift and even turn on side in case
of wheel lockup) shall be always within the ideal range to achieve the best braking effect through the braking
pressure control cycle of above “lock-unlock-lock-unlock”.
b. System self-diagnosis function

ECU integrates the self-diagnosis unit. It monitors the communications of input and output signals with
control unit. If the detected data of self-diagnosis unit fails to match those pre-stored in the system while the
vehicle is running, this unit will record this data as a fault data and store it into the control unit memory
module. ECU will determine the type of fault and enable relevant ABS control functions as per this fault data,
and it will control ABS fault indicator lamp of combination instrument to make it on and remind ABS of this
fault.

DI-104