Kia Forte: Failure Diagnosis

Second generation YD (2014-2018) / Kia Forte TD 2014-2018 Service Manual / Brake System / ESC(Electronic Stability Control) System / 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.	However, when 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.

Memory of Fail Code

1.	It keeps the code as far as the backup lamp power is connected. (O)

2.	It keeps the code regardless of the HECU power status but until the code is deleted. (X)

Failure Checkup

1.	Initial checkup is performed immediately after the HECU power on.

2.	Valve relay checkup is performed immediately after the IG2 ON.

3.	It executes the checkup all the time while the IG2 power is on.

Initial checkup is made in the following cases.

(1)	When no failure is detected

(2)	When ABS and ESC are not in control.

(3)	Initial checkup is not made after ECU power on.

(4)	If the vehicle speed is over 5 mph(8 km/h) when the brake lamp switch is off.

(5)	When the vehicle speed is over 24.8 mph(40 km/h).

5.	Though, it keeps on checkup even if the brake lamp switch is on.

6.	When performing ABS or ESC control before the initial checkup, stop the initial checkup and wait for the HECU power input again.

Judge 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.

Countermeasures In Fail

1.	Shut the system down and perform the following actions and wait for HECU power OFF.

2.	Turn the valve relay off depending on the failure situation.

3.	Do not perform any ABS/TCS/ESC functions until normal operating condition is restored.

Warning Lamp On

1.	ABS warning lamp turns on when ABS is malfunctioning.

2.	ESC function/ warning lamp turns on when ESC is malfunctioning.

When power voltage and valve relay voltage are abnormal, input/output related failure judgment is not made.

Standard Flow of Diagnostic Troubleshooting

Notes With Regard To Diagnosis

The phenomena listed in the following table are not abnormal.

Phenomenon

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.

ABS operation sound

1.	Sound of the motor inside the ABS hydraulic unit operation (whine).

2.	Sound is generated along with vibration of the brake pedal (scraping).

3.	When ABS operates, sound is generated from the vehicle chassis due to repeated brake application and release (Thump : suspension; squeak: tires)

ABS operation (Long braking distance)

For road surfaces such as snow-covered and gravel roads, the braking distance for vehicles with ABS can sometimes be longer than that for other vehicles. Accordingly, advise the customer to drive safely on such roads by lowering the vehicle speed.

Diagnosis detection conditions can vary depending on the diagnosis code. When checking the trouble symptom after
the diagnosis code has been erased, ensure that the requirements listed in "Comment" are met.

ABS Check Sheet

Problem Symptoms Table

Symptom

Suspect Area

ABS 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.

ABS does not operate intermittently.

Only when 1. ~ 4. are all normal and the problem is still occurring, replace the ABS 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 GDS
is not possible.
(Communication with any system is
not possible)

1.	Power source circuit

CAN line

Communication with GDS
is not possible.
(Communication with ABS only is
not possible)

1.	Power source circuit

CAN line

HECU

When ignition key is turned ON
(engine OFF),
the ABS warning lamp does not light up.

1.	ABS warning lamp circuit

HECU

Even after the engine is started, the ABS
warning lamp remains ON.

1.	ABS warning lamp circuit

HECU

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

Detecting condition

Trouble Symptoms

Possible Cause

Brake operation varies depending on driving conditions and road surface conditions, so diagnosis can be difficult. However if a normal DTC is displayed, check the following probable cause. When the problem is still occurring, replace the ESC control module.

-	Faulty power source circuit

-	Faulty wheel speed sensor circuit

-	Faulty hydraulic circuit for leakage

-	Faulty HECU

Inspection procedures

DTC Inspection

1.	Connect the GDS with the data link connector and turn the ignition switch ON.

2.	Verify that the DTC code is output. Is the DTC code output?

	▶ Check the power source circuit.
	▶ Erase the DTC and recheck using GDS.

Check the power source circuit

1.	Disconnect the connector from the ESC control module.

Turn the ignition switch ON, measure the voltage between terminal 32 of the ESC control module harness side connector and body ground.

Specification: approximately B+

Is the voltage within specification?

	▶ Check the ground circuit.
	▶ Check the harness or connector between the fuse (10A) in the engine compartment junction block and the ESC control module. Repair if necessary.

Check the ground circuit

1.	Disconnect the connector from the ESC control module.

2.	Check for continuity between terminals 13, 38 of the ESC control module harness side connector and ground point. Is there continuity?

	▶ Check the wheel speed sensor circuit.
	▶ Repair an open in the wire and ground point.

Check the wheel speed sensor circuit

1.	Inspect the wheel speed sensor circuit. (Refer to the DTC troubleshooting procedures) Is it normal?

	▶ Check the hydraulic circuit for leakage.
	▶ Repair or replace the wheel speed sensor.

Check the hydraulic circuit for leakage

1.	Inspect leakage of the hydraulic lines. Is it normal?

	▶ The problem is still occurring, replace the ABS control module.
	▶ Repair the hydraulic lines for leakage.

Detecting condition

Trouble Symptoms

Possible Cause

-	Faulty power source circuit

-	Faulty wheel speed sensor circuit

-	Faulty hydraulic circuit for leakage

-	Faulty HECU

Inspection procedures

DTC Inspection

1.	Connect the GDS with the data link connector and turn the ignition switch ON.

2.	Verify that the DTC code is output. Is the DTC code output?

	▶ Check the wheel speed sensor circuit.
	▶ Erase the DTC and recheck using GDS.

Check the wheel speed sensor circuit

1.	Refer to the DTC troubleshooting procedures. Is it normal?

	▶ Check the stop lamp switch circuit.
	▶ Repair or replace the wheel speed sensor.

Check the hydraulic circuit for leakage

1.	Inspection leakage of the hydraulic lines. Is it normal?

	▶ The problem is still occurring, replace the ABS control module.
	▶ Repair the hydraulic lines for leakage.

Detecting condition

Trouble Symptoms

Possible Cause

Possible defect in the power supply system (including ground) for the diagnosis line.

-	An open in the wire

-	Poor ground

-	Faulty power source circuit

Inspection procedures

Check The Power Supply Circuit For The Diagnosis

Measure the voltage between terminal 16 of the data link connector and body ground.

Specification : approximately B+

Is voltage within specification?

	▶ Check the ground circuit for the diagnosis.
	▶ Repair an open in the wire. Check and replace fuse (15A) from the engine compartment junction block.

Check the ground circuit for the diagnosis

1.	Check for continuity between terminal 4 of the data link connector and body ground. Is there continuity?

▶ Repair an open in the wire between terminal 4 of the data link connector and ground point.

Detecting condition

Trouble Symptoms

Possible Cause

When communication with GDS is not possible, the cause may be probably an open in the HECU power circuit or an open in the diagnosis output circuit.

-	An open in the wire

-	Faulty HECU

-	Faulty power source circuit

Inspection procedures

Check for Continuity in the CAN Line

1.	Disconnect the connector from the ESC control module.

2.	Check for continuity between terminals 26, 14 of the ESC control module connector and 6, 14 of the data link connector. Is there continuity?

	▶ Check the power source of ESC control module.
	▶ Repair an open in the wire.

Check the power source of ABS control module

1.	Disconnect the connector from the ABS control module.

Turn the ignition switch ON, measure the voltage between terminal 32 of the ESC control module harness side connector and body ground.

Specification : approximately B+

Is voltage within specification?

	▶ Check for poor ground.
	▶ Check the harness or connector between the fuse (10A) in the engine compartment junction block and the ABS control module.Repair if necessary.

Check for poor ground

Check for continuity between terminal 4 of the data link connector and ground point.

	▶ Replace the ESC control module and recheck.
	▶ Repair an open in the wire or poor ground

Detecting condition

Trouble Symptoms

Possible Cause

When current flows in the HECU the ABS warning lamp turns from ON
to OFF as the initial check. Therefore if the lamp does not light up, the
cause may be an open in the lamp power supply circuit, a blown bulb,
an open in the both circuits between the ABS warning lamp and the
HECU, and the faulty HECU.

-	Faulty ABS warning lamp bulb

-	Blown fuse is related to ABS in the engine compartment junction block

-	Faulty ABS warning lamp module

-	Faulty HECU

Inspection procedures

Problem verification

1.	Disconnect the connector from the ESC control module and turn the ignition switch ON.

Does the ABS warning lamp light up?

	▶ Inspect again after replacing the ESC HECU.
	▶ Check the power source for the ABS warning lamp.

Check the power source for the ABS warning lamp

1.	Disconnect the instrument cluster connector (M08) and turn the ignition switch ON.

Measure the voltage between terminal (M08) 22 of the cluster harness side connector and body ground.

Specification : approximately B+

Is voltage within specification?

	▶ Check the CAN circuit resistance for ABS warning lamp.
	▶ Check for blown fuse.

Check the CAN circuit resistance for ABS warning lamp

1.	Disconnect the instrument cluster connector (M08) and turn the ignition switch OFF.

2.	Measure the resistance

Circuit Diagram - ESC (4)

ESC Connector Input/ Out put Wire No. Designation Current max.permissible wire resistance R_L (mΩ) max min 1 ...

EBD(Electronic Brake-force Distribution)

The EBD system (Electronic Brake force Distribution) as a sub-system of the ABS system is to control the effective adhesion utilization by the rear wheels. It further utilizes the efficie ...

Kia Forte: Failure Diagnosis

Circuit Diagram - ESC (4)

EBD(Electronic Brake-force Distribution)

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