Hyundai Elantra: Inspection - Brake Booster Vacuum Pressure Sensor. Repair procedures - ISG (Idle Stop & Go) System - Fuel System - Hyundai Elantra MD 2010-2015 Service manualHyundai Elantra: Inspection

Check installation status of BBVPS and Vacuum hose or damage of vacuum hose.
Connect GDS to DLC (Data Link Cable).
Warm up the engine to normal operating temperature.
Monitor "BBVPS" parameter on GDS.

Fig.1) Idle Status
Fig.2) Brake pressure signal
With a brake partial vacuum that is too low, the ISG function also starts without activity on the part of the driver.
Insufficient brake partial vacuum can lead to safety risks during braking manoeuvres, when rolling on an incline. To prevent this, the engine is started.
(Refer to “DTC P0557, P0558” in DTC manual)