Chery A15. Manual — part 221

Chery A15 Maintenance Manual

(5). Large force required to operate brake pedal.

Possible Cause

[Description]
Check control booster and brake pedal travel with traditional
methods, and diagnose normally open valve with fault diagnoser
hydraulic control unit.

·

Booster problem

·

Normally open valve

problem

Abnormal

Replace HCU (hydraulic control unit)

Normal

(6). No fault code displayed (communication with fault diagnoser disabled).

Possible Cause

[Description]
This may be caused by open ABS ECU power circuit or
open diagnose circuit.

·

Fuse burned

·

Diagnose wire breakage or

connector looseness

·

ABS ECU damage

·

Fault diagnoser problem

No

Yes

Abnormal

Replace

Normal

Abnormal

No

Yes

No

Repair diagnose socket or ABS wire harness

Conduct

Replace ABS ECU

Check normally closed valve with hydraulic

control unit diagnosis of fault diagnoser

Check booster and pedal travel with

traditional ABS methods

Is the diagnoser able to communicate

with MK20 ABS ECU on other vehicles?

Check ABS power fuse

Diagnoser fault,
repair and retest

Dose diagnoser screen display?

Demount ABS ECU plug to check if the
related ECU terminal in ABS wire
harness (terminal 7 for MK20I/E) is
conducted to diagnose socket (terminal 7
in diagnoser)

Repair socket
or wire harness

Check power wire, earthing
wire and diagnose wire in
diagnose socket and their
connections

Chery A15 Maintenance Manual

VIII. ABS System Inspection

Terminal

Inspection Item

Ignition Switch

Position

MK20I/E

Standard Unit

Battery voltage
(motor)

OFF 25-8

10.1-14.5

V

Battery voltage
(electromagnetic valve)

↑ 9-24

↑ V

Power insulation

↑ 8-4

0.00-0.5

V

Earth insulation

↑ 8-24

↑ V

Power voltage

ON

8-4

10.0-14.5

V

OFF

Light off

Visual check

ON

ECU
disconnected

Light on

Visual check

OFF

Light off

Visual check

ABS warning light

ON

ECU
connected

Light on for 1.7s
and then off

Visual check

Brake light switch
function pedal
unpressed

ON 8-18

0.0-0.5 V

Brake light switch
function pedal pressed

ON 8-18

10.0-14.5

V

Front left wheel speed
sensor resistance

OFF 1-2 1.0-1.3 KΩ

Front right wheel speed
sensor resistance

OFF 19-20

1.0-1.3 KΩ

Rear left wheel speed
sensor resistance

OFF 5-6 1.0-1.3 KΩ

Rear right wheel speed
sensor resistance

OFF 22-23

1.0-1.3 KΩ

Front left wheel speed
sensor output voltage

OFF 1-2 3.4-14.8

mV/HZ

Front right wheel speed
sensor output voltage

OFF 19-20

3.4-14.8

mV/HZ

Rear left wheel speed
sensor output voltage

OFF 5-6 >12.2 mV/HZ

Rear

right

wheel speed

sensor output voltage

OFF 22-23

>12.2 mV/HZ

Sensor output voltage
ratio

Highest peak voltage

≦ 2

Lowest peak voltage

Chery A15 Maintenance Manual

IX. ABS Performance Inspection

(I). Checking Wheel Speed Sensor Output Voltage

1. Check the clearances between wheel speed sensors and gear rings, which shall

comply with standard values.

2. Jack up wheel and release hand brake.

3. Disconnect ABS wire harness and measure at harness adapter.

4. Rotate the wheel at the rate of 0.5 turn per second, and measure the output voltage

with a multimeter or an oscillograph.

MK20 I/E

Terminal 1 - 2

Terminal 19 – 20

Terminal 5 - 6

Terminal 22 – 23

5. Possible causes of output voltage exceeding above limits:

. Oversize air gap between sensor and gear ring

. Sensor fault

. Check sensor resistance, which shall be 1.0 - 1.3kΩ

. Check gear ring deformation and air gap between gear ring and wheel speed

sensor by taking four points on gear ring.

X. Disassembly and Assembly

(1). Spare Part Options

* HECU assembly, dry;

* Separate HCU and ECU, HCU wet.

(2). Precautions

* Identify fault cause with diagnoser before repair;

* Unpack spare parts only before installation;

* Use spare parts made by the same manufacturer;

* Wipe clean with only non-wool cloth;

Chery A15 Maintenance Manual

* Clean part surface with detergent free of mineral oil before manitenance;

* Do not use compressed air or move the vehicle when opening the system;

* Block all hydraulic outlets with proper plugs after ABS assembly is demounted;

* Remove other parts that may interfere with operation;

* Use DOT 4 brake fluid. Mineral oil is prohibited.

* Soak sealing part and O-ring in brake fluid. Mobile oil or brake grease are

prohibited.

* Check conventional brake system and ABS

performances after maintenance;

* Check all hydraulic pipe connections for leakage.

(3). Disassembling MK20-I HECU

. Turn off ignition switch and disconnect battery negative

terminal;

. Remove wire harness form ABS assembly;

. Depress the pedal >60mm and secure it with a pedal

4

3

2

1

B

A

bracket to shut off master pump center valve to prevent

brake fluid from flowing out from outlets when opening

system;

. First remove brake rigid tubes A and B connecting HCU

to master pump and mark the position, then plug up the

outlet immediately;

. Remove brake fluid tubes 1-4 connecting HCU to four

A Front piston B Rear piston
1 Front right 2 Rear left
3 Rear right 4 Front left

wheels and mark the position, then plug up the outlet

immediately;

. Remove the nut fixing HECU on bracket;

. Take the whole HECU off the bracket.