The Stop lamp switch signal is used for the Cruise Control, ABS-ESC, Shifter release as well as brake lights. The stop lamp switch consist of two seperate switches. One switch is open while the other switch is closed. When the brake pedal is not depressed, one circuit is system voltage while the other circuit is zero volts. When the brake pedal is depressed, the values of the two circuits are reversed. The ECM monitors the two signals and if it see both switches with the same value it will set the code.
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.
Item | Detecting Condition | Possible cause | |
DTC Strategy | Case1 |
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Comparing 2 brake signals during driving |
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Poor connection
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Open or short in Stop lamp switch
•
Faulty Stop lamp switch |
Case2 |
•
ECM detects stop lamp input signal when vehicle stops. | ||
Enable Conditions | Case1 |
•
Engine works
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Vehicle Speed Sensor is abnormal. Or
•
Engine works
•
Vehicle Speed Sensor is normal and Vehicle Speed is over 20kph dring 1sec or more. | |
Case2 |
•
Engine works
•
Vehicle Speed Sensor is normal and Vehicle Speed is over 20kph dring 1sec or more. | ||
Threshold value | Case1 |
•
The one brake signal's change duration when another signal has been changed > 0.5 sec | |
Case2 |
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Vehicle speed < 3kph
•
Vehicle acceleration < -6kph/s
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Stop lamp "OFF" and not changing of stop lamp signal for more 3 | ||
Diagnosis Time |
•
Continuous | ||
MIL On Condition |
•
NO MIL ON(DTC only) | ||
Item | During taking off the brake | During stepping on the brake |
Stop Lamp | 0V | Battery voltage |
Stop Lamp Switch | Battery voltage | 0V |
Fig.1) Normal data of Brake Switch during brake pedal released after depressed.
