The Stop lamp switch is used to judge whether the acceleration system is abnormal or not. The stop lamp switch has a duplex system(signals brake test or brake light) to memorize the abnormality when the signals of depressing and releasing the brake pedal are detected simultaneously.
Checking output signals from both Stop lamp 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, ECM sets P0504. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item
Detecting Condition
Possible cause
DTC Strategy
Comparing 2 brake signals during driving
Poor connection
Open or short in Stop lamp switch
Faulty Stop lamp switch
Enable
Conditions
Case 1
Engine works
Vehicle Speed Sensor is abnormal.
Case 2
Vehicle Speed Sensor is normal and Vehicle Speed is over 20kph dring 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
NO MIL ON(DTC only)
During taking off the brake
During stepping on the brake
Stop Lamp
0V
Battery voltage
Stop Lamp Switch
Fig.1) Normal data of Brake Switch during brake pedal released after depressed.