Brake switch connected to brake pedal transfers brake operating state to PCM. For diagnosis of abnormal operation of Brake switch, two types of signals(one from Brake warning lamp switch, the other from Brake checking switch) are used and those two types output different signals at both condition, depressing or releasing brake pedal. When brake pedal is depressed, brake checking switch outputs B+ voltage while brake warning lamp switch emits 0V. Conversly, when brake pedal is released, the output signals of each switch are opposite.
Checking output signals from both brake switch when all of them are On or OFF simultaneously, if abnormal signal is detected for more than 0.5 sec., an error is recognized. And if this condition lasts for certain period PCM sets P0504. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till cosecutive 2 driving cycle.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Comparing 2 brake signals during driving | ● Poor connection ● Open or Short ● Faulty PCM |
Enable Conditions | Case 1 | ● Engine works ● Vehicle Speed Sensor is abnormal. |
Case 2 | ● Engine works ● Vehicle Speed Sensor is normal and Vehicle Speed is over 20kph during 1sec or more. | |
Threshold value | ● The one brake signal’s change duration when another signal has been changed ＞ 0.5 sec | |
Diagnosis Time | ● Continuous | |
MIL On Condition | ● 2 driving cycles |
Item | During taking off the brake | During stepping on the brake |
Brake Lamp Switch | 0V | Battery voltage |
Brake Switch | Battery voltage | 0V |
