Chery A series. Manual — part 86
Normal
Replace the ABS ECU
No
Install it properly
Yes
Abnormal Abnormal
Replace
Normal Normal
Abnormal
Replace
Abnormal
Normal
Abnormal
Replace the ABS HCU
Repair or replace
Normal
Replace the connection
Normal
No
Normal
Abnormal
Repair the harness
or connector
ABS ECU
Sensor is installed properly or not
Check the sensor output voltage
Use the diagnostic tester to
conduct the HCU diagnosis
Check all sensors
Check all sensor gear rings
Check wheel bearing clearance
Check ABS ECU socket and
intermediate connector
Failure reoccurs or not
Refer to “Repair Details
of Random Failure”
Remove the ABS ECU connector, and check
whether the resistances between the
following terminals of ABS ECU conform to
the standard values?
Standard resistance: 1.0-1.3 k
Measure the resistances, and, at the same
time, swing the sensor harness and connector.
MK20I/E
FL wheel: 1-2 RR wheel: 19-20
RL wheel: 5-6 FR wheel: 22-23
Abnormal
Abnormal
P-38
Abnormal
Normal
Too long brake pedal travel
Possible Cause
[Description] Firstly take the visual inspection to
determine the outside leakage or
mechanical failure. Use the air bleeding
method to check the air in the system. And
use the diagnostic tester and hydraulic
testing to check the leakage of normally
closed valve (NC valve).
* Brake fluid leakage
* NC valve leakage
* Air kept in the system
* Serious brake disc
wear
* Hand brake
adjustment improper
Abnormal
Tighten the pipe joint according to the requirement
Normal
Abnormal
Replace the brake disc
Normal
Abnormal
Replace the hand brake adjusting equipment
Normal
Abnormal
Air bleeding again
Normal
Abnormal
Replace HCU (Hydraulic Control Unit)
Forcefully step on the brake pedal
Possible Cause
[Description] Use the traditional method to check and control
the booster and brake pedal travel. The failure of NO
(Normally Open) valve can be checked using the
diagnostic tester’s hydraulic control unit function.
* Booster failure
* NO valve failure
Replace HCU (Hydraulic Control Unit)
Visually inspect the leakage of hydraulic
Check the wear condition of brake
Check hand brake adjusting
Air bleeding check
Use the diagnostic tester HCU to
diagnose the sealing of NC valve
Use the diagnostic tester’s HCU to
diagnose and check the NO valve
Use the traditional method available
for ABS vehicle to check the booster
P-39
Abnormal
Yes
Normal
No
Abnormal
No
Replace
Yes
Yes
Without DTC output (fail to communicate with the diagnostic tester)
Possible Cause
[Description] If it is difficult to communicate with the
diagnostic tester, it is possible that the supply
circuit of ABS ECU or the diagnostic circuit is
open circuit.
* The fuse broken
* The diagnostic circuit
broken or the connection
uncoupled
* ABS ECU damaged
* Diagnostic tester failure
No
Repair the diagnostic socket or ABS harness
Replace the ABS ECU
The diagnostic tester communicates with the
MK20 ABS ECU on the other vehicles
Check ABS supply fuse
The diagnostic tester failure, and
conduct the check after repair
Display it on the screen of diagnostic tester or not
Remove ABS ECU’s connections, check the
connection of the ECU related terminals in
ABS harness (terminal 7 for MK20 I/E) with
the diagnostic socket (terminal 7 in the
diagnostic tester)
Check the supply,
earth, and
diagnostic wires
in the diagnostic
tester socket, and
their connection
Repair the diagnostic
tester socket or harness
P-40
ABS SYSTEM CHECK
Terminal
Check Item
Ignition
Position
MK20I/E
Standard Value
Unit
Battery voltage (motor)
OFF
25-8
10.1-14.5
V
Battery voltage (solenoid
valve)
9-24
V
Supply insulating property
8-4
0.00-0.5
V
Earth insulating property
8-24
V
Supply voltage
ON
8-4
10.0-14.5
V
OFF
Warning lamp
extinguishes
Visual
inspection
ON
ECU not
connected
Warning lamp
lights
Visual
inspection
OFF
Warning lamp
extinguishes
Visual
inspection
ABS warning lamp
ON
Connect the
ECU
The warning lamp
lights and then
extinguishes after
lasting for 1.7 s
Visual
inspection
Braking lamp switch
functional pedal not stepped
down
ON
8-18
0.0-0.5
V
Braking lamp switch
functional pedal stepped
down
ON
8-18
10.0-14.5
V
Resistance value of FL
wheel speed sensor
OFF
1-2
1.0-1.3
Resistance value of FR
wheel speed sensor
OFF
19-20
1.0-1.3
Resistance value of RL
wheel speed sensor
OFF
5-6
1.0-1.3
Resistance value of RR
wheel speed sensor
OFF
22-23
1.0-1.3
FL wheel sensor output
voltage
OFF
1-2
3.4-14.8
mV/HZ
FR wheel sensor output
voltage
OFF
19-20
3.4-14.8
mV/HZ
RR wheel sensor output
voltage
OFF
5-6
>12.2
mV/HZ
RR wheel sensor output
voltage
OFF
22-23
>12.2
mV/HZ
Sensor output voltage ratio
Maximum peak volt
2
Minimum peak volt
P-41
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