3.
Monitor "Brake Switch" parameter on the service data with stepping on and off the brake.
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 input signals from brake lamp switch under detecting condition, if the operation state of brake lamp switch does not change for more than 3 sec., PCM sets P0571. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till cosecutive 2 driving cycle.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● PCM detects brake lamp input signal when vehicle stops. | ● Poor connection ● Open or short to ground in signal circuit ● Faulty PCM | |
Enable onditions | ● Engine works ● Vehicle speed signal is normal. ● Vehicle speed 〉20kph (during 1sec or more) | ||
Threshold value | ● Vehicle speed 〈 3kph ● Vehicle acceleration〈 -6kph/s ● Brake lamp "OFF" and not changing of brake lamp signal for more 3 sec. | ||
Diagnosis Time | ● Continuous | ||
MIL On Condition | ● 2 driving cycles | ||
IG "OFF" ＆ connect scantool.
ENG "ON" and warm -up the engine to normal operating temperature.
Monitor "Brake Switch" parameter on the service data with stepping on and off the brake.
Are those related current data 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 "OFF".
Disconnect the PCM connector.
IG "ON" and ENG "OFF"
During taking off the brake : Measure the voltage between terminal 23 of PCM harness connector and chassis ground.
During stepping on the brake : Measure the voltage between terminal 23 of PCM harness 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 "OFF".
Disconnect the brake switch and PCM connector.
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 voltage" as follows.
▶ Repair open in circuit and go to "Verification of Vehicle Repair" procedure.
Check voltage
IG "OFF".
Disconnect the brake switch connector.
Measure the voltage between brake lamp switch terminal and chassis ground.
IG "ON" and ENG "OFF"
Measure the voltage between brake lamp switch terminal and chassis ground.
Item | During taking off the brake | During stepping on the brake | ||||||
Brake Lamp Switch | Battery voltage | Battery voltage | ||||||
Brake Switch | 0V | Battery voltage |
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.
