[Previous][Next]
Inspection Procedure 32: Brake Monitoring Switch System
 
 
 
 
CIRCUIT OPERATION
  • Battery voltage is applied to the stop light switch from the ECM connector terminal BRK.
 
 
COMMENT
  • The brake monitoring switch detects whether the brake pedal is depressed or not, and sends a signal to the ECM. The ECM compares the stop light signal sent from the ETACS-ECU via the CAN with the brake monitoring switch input signal, and determines whether the input information is reliable. In addition, it sends the brake monitoring switch signal information to other ECUs (such as ETACS-ECU or CVT-ECU) via the CAN.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case:)
  • Failed brake monitoring switch
  • Open/short circuit or harness damage in brake monitoring switch circuit or loose connector contact
  • Failed ECM
 
 
DIAGNOSIS
STEP 1. Check for height of brake pedal.
Check for height of brake pedal (Refer to GROUP 35A - On-vehicle Service - Brake Pedal Check And Adjustment ).
Is the brake pedal condition normal?
Go to Step 2.
Adjust the brake pedal height.
 
STEP 2. Check the brake monitoring switch.
Check the stop light switch (Refer to GROUP 35A - Brake Pedal - Inspection - Stop Light Switch Check ).
Is the switch condition normal?
Go to Step 3.
Replace the stop light switch.
 
STEP 3. Measure the voltage at brake monitoring switch connector
(1) Disconnect the connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal BRK line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 6.
Go to Step 4.
 
STEP 4. Check of short to ground, and open circuit in BRK line between stop light switch connector and ECM connector.
Is the harness wire in good condition?
Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 5. Check the trouble symptom.
Does the trouble symptom persist?
Replace the ECM.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
 
STEP 6. Check of open circuit, short circuit, and damage in ground line between stop light switch connector and body ground.
Is the harness wire in good condition?
Go to Step 7.
Repair the connector(s) or wiring harness.
 
STEP 7. Measure the sensor output voltage at ECM connector by backprobing.
(1) Do not disconnect the connector.
(2) Start the engine.
(3) Measure the voltage between terminal BRK line and ground by backprobing.
  • Voltage should be 1 volt or less when brake pedal released.
  • Voltage should be battery positive voltage when brake pedal depressed.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the measured voltage normal?
Go to Step 5.
Go to Step 8.
 
STEP 8. Check of damage in BRK line between brake monitoring switch connector and ECM connector.
Is the harness connector in good condition?
Replace the stop light switch.
Repair the connector(s) or wiring harness.