Anti-lock brake system (ABS control unit)
P-23
Noise
1. Self-tested sound system
After the engine started, short noise “Buzz” will come out from the engine compartment when a running
vehicle reached at 15km/h. It is a normal phenomenon as noise produced by the self-test of ABS control
unit.
2. Sound when the ABS control unit plays role
a. Motor sound from the hydraulic pressure unit of ABS control unit
b. Noise produced by the vibration together with the brake pedal
c. During the operation of ABS control unit, impact noise of suspension produced by the braking
3. If the noise is too loud when the system makes the self-test or the ABS control unit plays role, it
may be caused by the following reasons:
a. The fixation of ABS control unit and holder is loosened;
b. The fixation of ABS control unit holder with the bodywork is loosened
c. The connection fixing the brake lines is loosened
d. There are bulbs in the brake line.
Steps prior to determine the replacement of the ABS control unit
Dynamically self-check:
1. After the troubleshooting, the speed shall not be lower than 15km/h to enable the ABS control unit for a
dynamically self-check.
2. As the ABS control unit fault light will keep will not go off, the re-ignition is necessary after the
troubleshooting (e.g. the wheel speed sensor signal unstable or motor fault). Only when the vehicle
reached to about 15km/h and after the ABS control unit passed through the dynamically self-check, the
ABS control unit fault light can go off.
Cross validation:
Remove the ABS control unit and install on another trouble-free vehicle using an ABS control unit of same
model. It is only necessary to plug in the connector of ABS control unit sensor harness instead of oil pipe.
Reignite the vehicle and suspend it on a lifter and have it turn on air. Let the ABS control unit carry out the
dynamically self-check with the speed not lower than 15km/h.
1. If the alarm light of ABS control unit is still lit, it indicates that faults really exist in the ABS control unit.
The ABS control unit can be replaced.
2. If the alarm light of ABS control unit is off, it indicates that there are no faults in the ABS control unit.
Please rearrange the investigation as per the service manual
When operating according to the above steps, be sure that the ABS control units on two vehicles are of
same model and the ABS control unit plug tightly plugged in, otherwise it will result in unstable circuit.
Poor contact will cause the signal of wheel speed sensor distorted.
Requirements relevant to the Haima vehicle analysis for the product reject
The product warranty period provided by the Haima vehicle to the customer is 2 years, i.e. 60,000kms.
For the products, which are returned for the Haima vehicle analysis, an visual check shall be made at
First with the items as below:
1. No visual damages on the product
2. The ABS control unit not yet disassembled
3. No scratches on the ECU pins of ABS control unit
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