HILL LAUNCH ASSIST (HLA) OPERATES EVEN ON A DOWNHILL/HILL LAUNCH ASSIST (HLA) DOES NOT OPERATE ON A SLOPE [ELECTRONICALLY CONTROLLED BRAKE SYSTEM]

id040309892800

Troubleshooting item

Hill launch assist (HLA) operates even on a downhill

Hill launch assist (HLA) does not operate on a slope
Possible cause
Note
•  HLA operates on an up slope of about 6% or more when selector lever position is in a forward gear.
•  HLA operates on a down slope of about 6% or more when selector lever is in a R position.
•  HLA operates for a maximum of 2 s after releasing brake pedal.
•  Electronically controlled brake unit detects a malfunction (Input/output device malfunction).
•  PCM and/or instrument cluster detect a malfunction.
•  Sophisticated airbag sensor (SAS) control module installation malfunction (If there is a malfunction resulting from sophisticated airbag sensor (SAS) control module removal, HLA may not operate at desired inclination angle.)
•  Tire malfunction (Differing air pressure on four wheels, use of tires with differing conditions of wear)
•  Electronically controlled brake unit initial setting and low-G sensor initialization have not been performed after replacing electronically controlled brake unit and sophisticated airbag sensor (SAS) control module. (If initial setting and initialization are not performed, HLA may not operate at desired inclination angle.)
•  Center point of low-G sensor has deviated.
•  Input signal malfunction from ABS wheel-speed sensor
•  Input signal malfunction from PCM (Engine torque signal, engine speed signal, parking brake signal, accelerator pedal position signal, reverse gear signal, and clutch pedal signal)
•  Input signal malfunction from TCM (Selector lever position signal)
•  Communication error between electronically controlled brake unit and PCM
•  Communication error between electronically controlled brake unit and body control module (BCM)
•  Communication error between body control module (BCM) and instrument cluster
•  Brake (foot brake/parking brake) drag
System wiring diagram
Not applicable
Connector diagram
Not applicable

Diagnostic procedure

Step

Inspection

Results

Action
1
VERIFY DTC FOR RELATED MODULES
•  Retrieve the electronically controlled brake unit, PCM, TCM and instrument cluster DTC using the M-MDS.
•  Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [ELECTRONICALLY CONTROLLED BRAKE UNIT].)
(See DTC TABLE [PCM (SKYACTIV-G)].)
(See ON-BOARD DIAGNOSTIC SYSTEM DTC TABLE [TCM (ET6A-EL, ET6AX-EL)].)
(See DTC TABLE [BODY CONTROL MODULE (BCM)].)
No
Go to the next step.
2
VERIFY IF FALSE DETECTION OF INCLINATION ANGLE CAUSED BY MALFUNCTIONING SOPHISTICATED AIRBAG SENSOR (SAS) CONTROL MODULE INSTALLATION
•  Inspect the sophisticated airbag sensor (SAS) control module installation condition for the following:
―  Is the module installed with any twisting?
―  Is the module installed correctly?
Yes
Go to the next step.
No
Repair the sophisticated airbag sensor (SAS) control module installation condition, and perform the repair completion verification.
(See SAS CONTROL MODULE REMOVAL/INSTALLATION [TWO-STEP DEPLOYMENT CONTROL SYSTEM].)
3
VERIFY IF MALFUNCTION CAUSED BY INITIALIZATION PROCEDURE FOR LOW-G SENSOR NOT PERFORMED
•  Verify if malfunction caused by initialization procedure for low-G sensor not performed.
•  Has the initialization for the low-G sensor been performed after replacing the electronically controlled brake unit and the sophisticated airbag sensor (SAS) control module?
Yes
Go to the next step.
No
Perform the initialization procedure, and perform the repair completion verification.
(See ELECTRONICALLY CONTROLLED BRAKE UNIT RELATED PARTS SENSOR INITIALIZATION PROCEDURE.)
4
VERIFY IF MALFUNCTION CAUSED BY TIRE MALFUNCTION PERFORMED
•  Inspect the tire pressure and condition.
•  Are tire pressure and condition normal?
Yes
Go to the next step.
No
If the pressure is incorrect, adjust the tire pressure to the specification.
(See TIRE PRESSURE ADJUSTMENT.)
If the tires are worn, replace the tires.
Perform the repair completion verification.
5
INSPECT RELATED MODULES FOR MALFUNCTION CAUSED BY FALSE SIGNAL
•  Access the following electronically controlled brake unit, PCM and TCM PIDs using the M-MDS:
Electronically controlled brake unit
―  BRK_PEDAL_SW (Brake signal)
―  ACC_LON_C (Low-G sensor (longitudinal G) calculated value signal)
―  ACC_LON (Low-G sensor (longitudinal G) raw value signal)
―  BRK_FLD_PRES (Brake fluid pressure raw value signal)
―  WSPD_SEN_L/F (ABS wheel-speed sensor (LF) signal)
―  WSPD_SEN_R/F (ABS wheel-speed sensor (RF) signal)
―  WSPD_SEN_L/R (ABS wheel-speed sensor (LR) signal)
―  WSPD_SEN_R/R (ABS wheel-speed sensor (RR) signal)
PCM
―  ENG_RPM (Engine speed signal)
―  APP1 (APP sensor signal)
TCM
―  SHIFT_R (Transaxle range sensor signal)
―  SHIFT_N (Transaxle range sensor signal)
―  SHIFT_D (Transaxle range sensor signal)
―  SHIFT_A_M (Transaxle range sensor signal)
―  SHIFT_P (Transaxle range sensor signal)
•  Are all PID values normal?
Yes
Inspect the followings:
•  Brake (foot brake/parking brake) drag
•  Engine output malfunction
Repair or replace any malfunctioning parts according to the inspection result.
Perform the repair completion verification.
No
Inspect the related parts and wiring harness.
Repair or replace any malfunctioning parts according to the inspection result.
Perform the repair completion verification.
Repair completion verification
VERIFY THAT MALFUNCTION SYMPTOMS DO NOT RECUR AFTER REPAIR
•  Install/connect the part removed/disconnected during the troubleshooting procedure.
•  Has the malfunction symptom been eliminated?
Yes
Complete the symptom troubleshooting.
Explain to the customer what has been repaired.
No
Refer to the controller area network (CAN) malfunction diagnosis flow to inspect for a CAN communication error.
(See CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW.)
If the CAN communication is normal, perform the diagnosis from Step 1.