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Annex I Malfunction Cases and Incorrect Repair Cases
1. HECU Incorrect Repair Cases
① HECU replacement relating to ABS functioning noise
The HECU replacement case that deemed the noise of electromagnetic valve and motor as the
malfunction during the functioning of the ABS.
† During the functioning of ABS, the noise generated during the relieving or enhancing
of the braking pressure on various wheels is of normal functioning status. The noise
level will vary depending on the braking pressure applied on various wheels, other than
the product malfunction. Therefore, we should persuade the customers to understand
that.
† When the vehicle reaches 10km/h speed at the first time after vehicle start, the sensitive
customers may hear the noise at the time when the ECU diagnoses the motor drive,
which is also the normal functioning of the ABS.
② HECU replacement relating to EBD functioning noise
The HECU replacement case that deemed the clattering noise of rear wheels that other than
the ABS functioning noise during the braking as the malfunction.
† The ABS is also equipped with EBD function, which will effect the relieving of
braking pressure on the rear wheels when the rear wheels are locked ahead of the front
wheels. The noise generated during the above mentioned process is of normal
functioning status.
③ HECU replacement relating to braking off-tracking
HECU replacement case due to the vehicle braking off-tracking towards one side during the
braking.
† ABS is the braking assisted device that functioning in such manner that the ECU will
calculate the speed of various wheels in order to maintain the best braking force and
control stability during the braking. In the event of malfunction of the HECU, the ECU
will illuminate the warning lamp by means of the diagnosis. Therefore, in the event of
braking off-tracking without the illumination of ABS warning lamp, it’s necessary to
check other braking hydraulic devices.
† In the event of incorrect assembling of the braking hose, the braking off-tracking may
occur during the functioning of the ABS.
④ Replacement case that the ABS is functioning during barking at low speed (below 40km/h)
HECU and sensor replacement case that the ABS is always functioning during the braking at
low speed.
† During the braking at low speed, the ABS may also function depending on the road
conditions and braking pressure. If the ABS is always functioning at each time, it’s
necessary to check if the sensor air gap of various wheels is too large, if it has
interference with the gear ring, and if the tooth shape of the gear ring is damaged.
† Air gap adjustment method. For the improper air gap, after the determination of the
parts related to the problem, replace or grind the installation surface (junction portion)
of the sensor to the specified air gap; in the event of interference, place the thin gasket
onto the sensor installation surface so as to adjust to the specified air gap.
2. Incorrect Repair Cases for Wheel Speed Sensor
① Open-circuit and short-circuit related to sensor
The sensor replacement case without product checking when the ABS warning lamp is
illuminated and the trouble code of the vehicle is determined.
† The ABS trouble code is prepared based on the ABS products. Therefore, during the
open-circuit or short-circuit of the sensor, it’s necessary to conduct the problem
checking, such as confirm the connection status from the ECU to the wiring and
connectors of the sensor, measure the sensor resistance, and etc. During the
malfunction checking of sensor, it’s preferable to use the tetrastyle jack, which will
facilitate the confirmation of short-circuit problems such as the pinned wiring.
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