3.
Monitor "Brake Switch" parameter on Current Data
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 |
Ignition "OFF"
Connect Scantool and Engine "ON"
Monitor "Brake Switch" parameter on Current Data
Are those "Brake Switch" parameters displayed correctly ?
▶ Fault is intermittent caused by poor contact in Sensor’s and/or PCM’s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "Terminal and Connector Inspection" procedure.
Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to " Power Circuit Inspection " procedure.
Check voltage
IG Key "OFF".
Disconnect the PCM connector.
IG Key "ON" and keep the brake taking off.
Measure the voltage between terminal 21 of PCM connector and chassis ground.
Measure the voltage between terminal 23 of PCM connector and chassis ground .
Keep the brake stepping on.
Measure the voltage between terminal 21 of PCM connector and chassis ground.
Measure the voltage between terminal 23 of PCM connector and chassis ground .
Item | During taking off the brake | During stepping on the brake | ||||||
Brake Lamp Switch | 0V | Battery voltage | ||||||
Brake Switch | Battery voltage | 0V |
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
IG Key "OFF".
Disconnect the brake switch and PCM connector.
Measure the resistance between terminal 21 of PCM harness connector and terminal 3 of Brake switch harness side.
Measure the resistance between terminal 23 of PCM harness connector and terminal 1 of Brake switch harness side.
Specification : Approx. below 1Ω
Is the measured resistance within specification ?
▶ Go to "Check voltagen" procedure.
▶ Repair open in circuit and go to "Verification of Vehicle Repair" procedure.
Check voltage
IG Key "OFF".
Disconnect the brake switch connector.
Measure the voltage between brake lamp switch terminal and chassis ground.
Measure the voltage between brake switch terminal and chassis ground.
IG Key "ON".
Measure the voltage between brake lamp switch terminal and chassis ground.
Measure the voltage between brake switch terminal and chassis ground.
Item | During taking off the brake | During stepping on the brake | ||||||
Brake Lamp Switch | 0V | Battery voltage | ||||||
Brake Switch | Battery voltage | 0V |
Is the measured voltage within specification ?
▶ Substitute with a known - good brake switch and check for proper operation. If the problem is corrected, replace brake switch and go to "Verification of Vehicle Repair" procedure.
▶ Check the fuse between battery and brake switch.
▶ Repair open or short in power circuit of brake switch and go to "Verification of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
Using a Scantool, Clear the DTCs
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
Monitor that all rediness test have been verified as " Complete "
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
