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Inspection Procedure 11: The stoplight switch signal is not received.
 
 
cautionBefore replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
TECHNICAL DESCRIPTION (COMMENT)
The stoplight switch input signal is used for the operation judgment of the functions below. If the signal is abnormal, these functions will not work.
  • ASC
  • OSS
  • Cruise control system
 
 
TROUBLESHOOTING HINTS
  • The stoplight switch may be defective
  • The stoplight relay* may be defective
  • The ETACS-ECU may be defective
  • The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
note*: The stoplight relay cannot be inspected because it is a semiconductor relay.
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Check the stoplight switch.
Check the stoplight switch. Refer to GROUP 35A - Brake Pedal .
Is the check result normal?
Go to Step 2.
Replace the stoplight switch.
 
STEP 2. Voltage measurement at ETACS-ECU connector (BKLP terminal).
(1) Measure by backprobing without disconnecting the ETACS-ECU connector and stoplight switch connector.
(2) Check the voltage between the ETACS-ECU connector (BKLP terminal) and ground.
OK:
  • When the brake pedal is released: Approximately 0 V - 5 V (pulse)
  • When the brake pedal is depressed: Approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 5.
Go to Step 3.
 
STEP 3. Check of short to power supply, short to ground, and open circuit in BKLP line between ETACS-ECU connector and stoplight switch connector.
Is the check result normal?
Go to Step 4.
Repair the connector(s) or wiring harness
 
STEP 4. Check of short to ground, and open circuit in STP line between ETACS-ECU connector and stoplight switch connector.
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness
 
STEP 5. Using scan tool (M.U.T.-IIISE), check data list.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect Scan Tool (M.U.T.-IIISE) ."
(2) Temporarily replace the stoplight relay, and then depress the brake pedal.
 
Item No.Item nameNormal condition
290Stoplight switchON
OK: Normal condition is displayed.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the ETACS-ECU.