VEHICLE MOVES WHEN ACCELERATING FROM STANDSTILL ON SLOPE [SKYACTIV-G]

id1103sb002700

Troubleshooting item

Vehicle moves when accelerating from standstill on slope
Description
•  Vehicle slips backwards on inclined road surface when accelerating after i-stop operates.
Possible cause
Note
•  MTX vehicles do not have the Hill Launch Assist function from i-stop because the driver controls the brake pressure.
•  i-stop (engine-stop control) continues operating when shifting the selector lever from D position to N or P position while i-stop (engine-stop control) is operating, however, if the slope of the road surface is within ±4%, the Hill Launch Assist (HLA) function is canceled.
Hill launch assist function system (DSC) malfunction
•  False detection of inclination angle (cannot calculate correct road slope)
―  Low-G sensor (built-into SAS control module) malfunction
―  Low-G sensor (built-into SAS control module) initialization malfunction
•  False detection of brake fluid pressure
―  Brake fluid pressure sensor (built-into DSC HU/CM) malfunction (without Mazda M Hybrid)
―  Brake fluid pressure sensor (built-into electronically controlled brake unit) malfunction (with Mazda M Hybrid)
•  Cannot maintain brake fluid pressure
―  DSC HU/CM malfunction (without Mazda M Hybrid)
―  Electronically controlled brake unit malfunction (with Mazda M Hybrid)
•  DC-DC converter system error (exceeds capacity of DC-DC converter output due to open or short circuit in wiring harness and after-market electrical part)
ATX system malfunction
•  Electric AT oil pump malfunction (operation malfunction, insufficient pressure)
•  ATX malfunction
System wiring diagram
•  Not applicable
Connector diagram
•  Not applicable

Diagnostic procedure

Step

Inspection

Results

Action
1
INSPECT EFFECT OF NON-GENUINE ELECTRICAL ACCESSORY FOR CAUSE OF MALFUNCTION
•  Remove any non-genuine electrical accessory.
•  Verify the malfunction symptom.
•  Does vehicle slip backwards on inclined road surface when accelerating after i-stop operates?
Yes
Go to the next step.
No
The system is normal.
•  Explain to the customer that the vehicle slips backwards on an inclined road surface when accelerating after i-stop operates due to the effect of the non-genuine electrical accessory installed.
2
VERIFY DTC
•  Perform the DTC inspection for the following modules.
―  PCM
―  TCM
―  DSC HU/CM (without Mazda M Hybrid)
―  Electronically controlled brake unit (with Mazda M Hybrid)
―  SAS control module
―  DC-DC converter (Mazda M Hybrid)
•  Are any DTCs displayed?
Yes
Repair the malfunctioning location according to the applicable DTC troubleshooting.
(See DTC TABLE [PCM (SKYACTIV-G (E))].)
(See ON-BOARD DIAGNOSTIC SYSTEM DTC TABLE [TCM (CW6A-EL)].)
(See ON-BOARD DIAGNOSTIC SYSTEM DTC TABLE [TCM (ET6A-EL, ET6AX-EL) (E)].)
(See ON-BOARD DIAGNOSTIC SYSTEM DTC TABLE [TCM (EV6A-EL) (E)].)
(See DTC TABLE [DSC HU/CM (E)].)
(See DTC TABLE [ELECTRONICALLY CONTROLLED BRAKE UNIT].)
(See DTC TABLE [SAS CONTROL MODULE].)
(See DTC TABLE [DC-DC CONVERTER (Mazda M Hybrid)].)
No
Go to the next step.
3
DETERMINE IF MALFUNCTION CAUSE IS HILL LAUNCH ASSIST FUNCTION OR ATX SYSTEM
•  Verify the malfunction symptom on a flat road surface.
•  Does the acceleration lag when accelerating?
Yes
Perform the symptom troubleshooting “ACCELERATION MALFUNCTION”.
(See ACCELERATION MALFUNCTION [SKYACTIV-G].)
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 [(E)].)
•  If the CAN communication is normal, repeat the inspection from Step 1.
―  If the malfunction recurs, perform the following procedure.
Without Mazda M Hybrid:
•  Replace the DSC HU/CM. (Brake fluid pressure sensor (built-into DSC HU/CM) or DSC HU/CM brake pressure hold function malfunction.)
With Mazda M Hybrid:
•  Replace the electronically controlled brake unit. (Brake fluid pressure sensor (built-into electronically controlled brake unit) or electronically controlled brake unit brake pressure hold function malfunction.)
―  Perform the repair completion verification 1.
Repair completion verification 1
VERIFY THAT VEHICLE IS REPAIRED
•  Install/connect the part removed/disconnected during the troubleshooting procedure.
•  Has the malfunction symptom been eliminated?
Yes
Complete the symptom troubleshooting. (Explain contents of repair to customer)
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 [(E)].)
•  If the CAN communication is normal, perform the diagnosis from Step 1.
―  If the malfunction recurs, go to the next step.
Repair completion verification 2
VERIFY IF MALFUNCTION IS CAUSED BY NOT PERFORMING PCM REPROGRAMMING
•  Verify repair information and verify that there is a new calibration in the PCM.
•  Is there a new calibration in the PCM?
Yes
Perform the PCM reprogramming and verify if the malfunction symptom was corrected.
•  If the malfunction recurs, replace the PCM.
No
Replace the PCM.
(See PCM REMOVAL/INSTALLATION [SKYACTIV-G (WITHOUT CYLINDER DEACTIVATION (E))].)
(See PCM REMOVAL/INSTALLATION [SKYACTIV-G (WITH CYLINDER DEACTIVATION (E))].)