VERACRUZ(EN) >2009 > G 3.8 DOHC > Fuel System > Engine Control System>P0504 Brake Switch \'A\' / \'B\' Correlation  
General Description
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.
DTC Description
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, PCM sets P0504. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC Detecting Condition
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 running
•
Vehicle Speed Sensor is abnormal.
Case 2
•
Engine running
•
Vehicle Speed Sensor is normal and Vehicle Speed is over 20kph druing 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

Specification
Item
 Brake OFF
 Brake ON
Stop Lamp
 0V
 Battery voltage
Stop Lamp Switch
 Battery voltage
 0V

Schematic Diagram

Monitor DTC Status
1.
Check DTC Status
(1)
Connect scantool to Data Link Connector(DLC).
(2)
IG "ON".
(3)
Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.
(4)
Read "DTC Status" parameter.

(5)
Is parameter displayed "Present fault"?

 ▶ Go to "Terminal and connector inspection" procedure.

 ▶ Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Terminal And Connector Inspection
1.
Many malfunctions in the electrical system are caused by poor harness and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3.
Has a problem been found?

 ▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure

 ▶ Go to " Power Circuit Inspection " procedure.

Power Circuit Inspection
■ Check voltage
1.
IG Key "OFF".
2.
Disconnect the PCM connector.
3.
IG Key "ON" and keep the brake taking off. (Measurement "A")
4.
Measure the voltage between brake switch signal terminal of PCM harness connector and chassis ground.
5.
Measure the voltage between brake lamp signal terminal of PCM harness connector and chassis ground .
6.
Keep the brake stepping on.(Measurement "B")
7.
Measure the voltage between brake switch signal terminal of PCM harness connector and chassis ground.
8.
Measure the voltage between brake lamp signal terminal of PCM harness connector and chassis ground.
Specification :
Item
 Brake OFF
 Brake ON
Stop Lamp
 0V
 Battery voltage
Stop Lamp Switch
 Battery voltage
 0V

9.
Is the measured voltage within specification ?

 ▶ Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair as necessary and go to "Verification of Vehicle Repair" procedure.

 ▶ Go to "Check open in harness" as follows.

■ Check open in harness
1.
IG Key "OFF".
2.
Disconnect the stop lamp switch and PCM connector.
3.
Measure the resistance between brake switch signal terminal of PCM harness connector and brake switch signal terminal of Stop lamp switch harness connector.
4.
Measure the resistance between brake lamp signal terminal of PCM harness connector and brake lamp signal terminal of Stop lamp switch harness connector.
Specification : Approx. below 1Ω
5.
Is the measured resistance within specification ?

 ▶ Go to "Check Battery voltagen" procedure.

 ▶ Repair open in circuit and go to "Verification of Vehicle Repair" procedure.

■ Check battery voltage
1.
IG Key "OFF".
2.
Disconnect the stop lamp switch connector.
3.
Measure the voltage between power supply terminals of stop lamp switch harness connector and chassis ground.
4.
IG Key "ON".
5.
Measure the voltage between power supply terminals of stop lamp switch harness connector and chassis ground.
Specification :
Item
 Brake OFF
 Brake ON
Stop Lamp
 Battery voltage
 Battery voltage
Stop Lamp Switch
 0V
 Battery voltage

6.
Is the measured voltage within specification ?

 ▶ Substitute with a known - good stop lamp switch and check for proper operation. If the problem is corrected, replace stop lamp switch and go to "Verification of Vehicle Repair" procedure.

 ▶ Check the fuse between battery and stop lamp switch.
▶ Repair open or short in power circuit of stop lamp switch and go to "Verification of Vehicle Repair" procedure.

Verification Of Vehicle Repair
After a repair, it is essential to verify that the fault has been corrected.
1.
Connect scantool and select "DTC" button.
2.
Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3.
Read "DTC Status" parameter
4.
Is parameter displayed "History(Not Present) fault"?

 ▶ System performing to specification at this time. Clear the DTC

 ▶ Go to the applicable troubleshooting procedure.