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Inspection Procedure 3: Stoplight does not illuminate or go out normally. <Vehicles with stop light relay>
 
 
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
If the stoplights do not illuminate or go out normally, the stoplight relay power supply, ground circuit system, stoplight switch, or the stoplight relay * may be defective.
note*: The stoplight relay cannot be inspected because it is a semiconductor relay.
 
 
PROBABLE CAUSES
  • Malfunction of stoplight switch
  • Malfunction of stoplight relay
  • Damaged harness wires and connectors
 
 
DIAGNOSIS
Required Special Tools:
  • MB992006: Extra fine probe
  • MB991223: Harness set
STEP 1. Check stoplight relay connector C-29 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Is stoplight relay connector C-29 in good condition?
Go to Step 2.
Repair the damaged parts
 
STEP 2. Resistance measurement at stoplight relay connector C-29.
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between stoplight relay connector C-29 (terminal No. 6) and the body ground.
OK: The measured value should be continuity exists (2 ohms or less).
Does the measured resistance value correspond with this range?
Go to Step 4.
Go to Step 3.
 
STEP 3. Check the wiring harness between stoplight relay connector C-29 (terminal No. 6) and ground.
Check the ground line for open circuit.
Is the wiring harness between stoplight relay connector C-29 (terminal No. 6) and ground in good condition?
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to use Troubleshooting/inspection Service Points, How to Cope with Intermittent Malfunction ).
Repair the wiring harness.
 
STEP 4. Check the stoplight switch.
Check the stoplight switch. Refer to GROUP 35A - Brake Pedal .
Is the stoplight switch in good condition?
Go to Step 5.
Replace the stoplight switch.
 
STEP 5. Check the battery power supply circuit to the stoplight relay. Measure the voltage at stoplight relay connector C-29.
(1) Disconnect stoplight relay connector C-29 measure the voltage available at the wiring harness side of the connector.
(2) Measure the voltage between stoplight relay connector C-29 terminal 4 and ground.
  • The voltage should measure approximately 12 volts (battery positive voltage).
(3) Stoplight switch: ON
(4) Measure the voltage between stoplight relay connector terminal No. 3 and the body ground.
  • The voltage should measure approximately 12 volts (battery positive voltage).
Is the measured voltage approximately 12 volts (battery positive voltage)?
Go to Step 11.
Go to Step 6.
 
STEP 6. Check ETACS-ECU connector C-403 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Is ETACS-ECU connector C-403 in good condition?
Go to Step 7.
Repair the damaged parts
 
STEP 7. Check the wiring harness between stoplight relay connector C-29 (terminal No. 3/4) and ETACS-ECU connector C-403 (terminal No. 1).
  • Check the power supply line (battery supply) for open circuit and short circuit.
Is the wiring harness between stoplight relay connector C-29 (terminal No. 3/4) and ETACS-ECU connector C-403 (terminal No. 1) in good condition?
Go to Step 8.
Repair the wiring harness.
 
STEP 8. Check ETACS-ECU connectors C-410 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Is ETACS-ECU connectors C-410 in good condition?
Go to Step 9.
Repair the damaged parts.
 
STEP 9. Check the battery power supply circuit to the ETACS-ECU. Measure the voltage at ETACS-ECU connector C-410.
(1) Disconnect connector measure the voltage available at the wiring harness side of the connector.
(2) Disconnecting the ETACS-ECU connector C-410.
(3) Stoplight switch: ON
(4) Measure the voltage between ETACS-ECU connector C-410 terminal No. 16 and the body ground.
  • The voltage should measure approximately 12 volts (battery positive voltage).
Is the measured voltage approximately 12 volts (battery positive voltage)?
Go to Step 11.
Go to Step 10.
 
STEP 10. Check the wiring harness between ETACS-ECU connector C-410 (terminal No. 16) and stoplight relay connector C-29 (terminal No. 3).
  • Check the signal line for short circuit.
Is the wiring harness between ETACS-ECU connector C-410 (terminal No. 16) and stoplight relay connector C-29 (terminal No. 3) in good condition?
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to use Troubleshooting/inspection Service Points, How to Cope with Intermittent Malfunction ).
Repair the wiring harness.
 
STEP 11. Check the wiring harness between stoplight relay connector C-29 (terminal No. 1) and intermediate connector C-28 (terminal No. 24).
Check the communication line for open or short circuit.
Is the wiring harness between stoplight relay connector C-29 (terminal No. 1) and intermediate connector C-28 (terminal No. 24) in good condition?
Go to Step 12.
Repair the wiring harness.
 
STEP 12. Retest the system
Check that the stoplight illuminates normally.
Does the stoplight relay work normally?
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 stoplight relay.