DTC P0703: Malfunction of Stoplight Switch: Diagnosis

STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to perform the CAN bus diagnosis.

Q: Is the check result normal?
1. YES: Go to Step 2.
2. NO: Repair the CAN bus lines (Refer to DIAGNOSTIC TROUBLE CODE TABLE ).
STEP 2. M.U.T.-III data list
Item 50: Brake switch

OK: The service data changes in response to the brake operation.

Q: Is the check result normal?
1. YES: Intermittent malfunction
2. NO: Go to Step 3.
STEP 3. Check the following connector:
- C-304 ETACS-ECU connector
- C-312 ETACS-ECU connector
- C-32 Stoplight switch connector
Check the contact status of the terminals.

Q: Is the check result normal?
1. YES: Go to Step 4.
2. NO: Repair the defective connector.
STEP 4. Stoplight Switch Check
Refer to STOPLIGHT SWITCH CHECK .

Q: Is the check result normal?
1. YES: Go to Step 5.
2. NO: Replace the stoplight switch.
STEP 5. Check for open circuit in the wiring harness between the stoplight switch connector and the ETACS-ECU connector.
Between C-32 Stoplight switch connector (terminal No. 2) and C-304 ETACS-ECU harness-side connector (terminal No. 1)

Q: Is the check result normal?
1. YES: Go to Step 6.
2. NO: Repair the wiring harness.
STEP 6. Symptom recheck after erasing diagnostic trouble code
Q: Is the check result normal?
1. YES: Intermittent malfunction
2. NO: Replace the ETACS-ECU, and then go to Step 7.
STEP 7. Symptom recheck after erasing diagnostic trouble code
Q: Is the check result normal?
1. YES: Intermittent malfunction
2. NO: Replace TCM.