The ABS ECU(Electronic Control Unit) checks the battery voltage to determine, as a safety issue, whether the ABS system can operate normally or not. The normal battery voltage range is essential for controlling the ABS system as instended.
The ABS ECU monitors the battery voltage by reading the value of voltage. When the voltage is lower than the expected normal value, this code is set. The ABS/ESP functions are prohibited and the EBD function is allowed on LOW VOLTAGE CONDITION, the ABS/EBD/ESP functions are prohibited on UNDER VOLTAGE CONDITION. If the voltage recovers, to within normal operating ranges, then the controller returns to normal operations as well.
Item
Detecting Condition
Possible cause
DTC Strategy
Battery Voltage Monitoring
Poor connection in power supply circuit (IGN+)
Faulty Alternator
Faulty HECU
Monitoring Period
Continuous (Under voltage faults are only entered in the EEPROM if the vehicle speed is > 6km/h.)
Case1
(Low voltage)
Enable
Conditions
When Vign is lower than 9.3V outside ABS/ESP control.
When Vign is lower than 9.2V inside ABS/ESP control.
- If IGN voltage is recovered to 9.6V, the system recovers to normal state.
- The monitored supply voltage is filtered and limited to a rise time of 4 volts per second.
Fail
Safe
The ABS/ESP functions are inhibited.
The ABS/ESP warning lamps are activated.
Case2
(Under voltage)
When Vign is lower than 7.7V.
- If IGN voltage is recovered to 7.8V, the system recovers to normal state.
The ABS/EBD/ESP functions are inhibited.
The ABS/EBD/ESP warning lamps are activated.