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Kia Sorento: Troubleshooting - Electronic Stability Control (ESC) - Brake SystemKia Sorento: Troubleshooting

Kia Sorento (MQ4, 2021-2026) Service Manual / Brake System / Electronic Stability Control (ESC) / Troubleshooting

Troubleshooting
Failure Diagnosis
1.
In principle, ESC and TCS controls are prohibited in case of ABS failure.
2.
When ESC or TCS fails, only the failed system control is prohibited.
3.
The solenoid valve relay should be turned off in case of ESC failure, refer to the ABS fail-safe.
4.
Information on ABS fail-safe is identical to the fail-safe in systems where ESC is not installed.
Failure Code Memory
1.
It keeps the code as far as the backup lamp power is connected.
2.
It stores the code as long as HECU is powered ON.
Failure Test
1.
Initial test is performed immediately after the HECU is powered on.
2.
Valve relay test is performed immediately after switching "ON" the IG2.
3.
Test are performed at all times the ignition (IG2) is ON.
4.
Initial test is performed in the following cases.
(1)
When the failure is not detected momentarily
(2)
When ABS and ESC are not in control.
(3)
If initial test is not made after supplying power to ECU.
(4)
If the vehicle speed is over 5 mph (8 km/h) with the brake lamp switched off.
(5)
When the vehicle speed is over 24.8 mph (40 km/h).
5.
Test continues even if the brake lamp is switched on.
6.
When performing ABS or ESC control before the initial test, stop the initial test and wait for the HECU power input again.
7.
Determining failure in the following cases.
(1)
When the power is normal.
(2)
From the point in which the vehicle speed reaches 4.9 mph(8 km/h) after HECU power on.
Failure Countermeasures
1.
Turn the system down and perform the following actions and wait for HECU to power OFF.
2.
Turn the valve relay off.
3.
Stop the control during the operation and do not execute anything until it recovers to normal condition.
Warning Lamp ON
1.
ESC warning lamps turns on for 3 seconds after IGN ON.
2.
ESC function lamp blinks when ESC Activated.
3.
In case of ESC failure, ESC warning lamp turns ON.
4.
ESC OFF lamp turns on:
– When ESC is switched OFF
–3 seconds after IGN ON
Standard Flow of Diagnostic Troubleshooting

Brake System — Electronic Stability Control (ESC) / Troubleshooting illustration

Notes With Regard To Diagnosis
The conditions listed in the following table are not abnormal.
Condition
 Explanation
System check sound
 When starting the engine, a thudding sound can sometimes be heard coming
from inside the engine compartment. This is because the system operation
check is being performed.
ESC operation sound
1)
Sound of the motor inside the ESC hydraulic unit operation (whine).
2)
Sound is generated along with vibration of the brake pedal (scraping).
3)
When ESC operates, sound is generated from the vehicle chassis due to
repeated brake application and release
(Thump : suspension; squeak: tires)
ESC operation
(Long braking distance)
 On snow-covered or gravel roads, the braking distance for vehicles with ABS can sometime be longer than that of vehicles without ESC. Accordingly, advise customers to drive safely on such roads by reducing the vehicle speed.
Diagnostic detection conditions can vary depending on the diagnostic code.
When checking the trouble symptom after the diagnostic code has been erased, ensure that the requirements listed in "Comment" are met.

Checklist for diagnosis of ESC system
Before and after the ESC system test, Do these steps to check the integrity of the warning lamp and ESC system.
1.
Inspection method
Turn on the IGN and check ABS system: If ABS/BRAKE warning lamp illuminate for 3 seconds, warning lamp and ABS system are in normal condition.
(1)
When the warning lamp does not illuminate when the IGN is turned on.
1)
Remove the ABS ECU connector in the engine room.
2)
Turn on the IGN.
3)
When the ABS / BRAKE warning light does not light up:
This is a warning light related problem, so check the instrument panel and wiring.
4)
When the ABS / BRAKE warning light remains lit:
The warning light is normal and judged to be an ESC system error. Check the ESC system using KDS.
(2)
If the warning lamp illuminates and does not off.
1)
Do the self test using KDS.
2)
Record the fault code after self test.
3)
Work with the recorded fault code and self test using KDS.
4)
If there are no faults after self test: test the IGN to verify normal condition.
5)
If there are faults after self test: do the inspection using the fault code check list.
2.
If there are faults after self-test using KDS even if ESC system and warning lamp are in normal condition, record the fault code and work with it.
Note
1)
Make sure the IGN is switched off when removing or installing connectors.
2)
If a warning lamp illuminates or abnormal occurs during a driving test, make an inspection sheet.
ESC Check Sheet

Brake System — Electronic Stability Control (ESC) / Troubleshooting illustration

Problem Symptoms Table
Symptom
 Suspect Area
ESC does not operate.
 Only when 1 - 4 are all normal and the problem is still occurring, replace the HECU.
1)
Check the DTC reconfirming that the normal code is output.
2)
Power source circuit.
3)
Speed sensor circuit.
4)
Check the hydraulic circuit for leakage.
ESC does not operate intermittently.
 Only when 1 - 4 are all normal and the problem is still occurring, replace the ESC actuator assembly.
1)
Check the DTC reconfirming that the normal code is output.
2)
Wheel speed sensor circuit.
3)
Stop lamp switch circuit.
4)
Check the hydraulic circuit for leakage.
Communication with KDS
is not possible.
(Communication with any system is
not possible)
1)
Power source circuit
2)
CAN line
Communication with KDS
is not possible.
(Communication with ESC only is
not possible)
1)
Power source circuit
2)
CAN line
3)
HECU
When ignition key is turned ON
(engine OFF),
the ESC warning lamp does not light up.
1)
ESC warning lamp circuit
2)
HECU
Even after the engine is started, the ESC
warning lamp remains ON.
1)
ESC warning lamp circuit
2)
HECU

Caution
During ESC operation, the brake pedal may vibrate or may not be able to be depressed. Such conditions are due to intermittent changes in hydraulic pressure inside the brake line to prevent the wheels from locking and is not an abnormality.
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