Inspection Procedure 1: The Low-beam Headlamps do not Illuminate Normally. <Using SWS Monitor>


caution Whenever the ECU is replaced, ensure that the input and output signal circuits are normal.




COMMENTS ON TROUBLE SYMPTOM
If the low-beam headlamps do not illuminate, the headlamp switch input circuit or the front-ECU may be defective.

PROBABLE CAUSES

  • Malfunction of the column switch
  • Malfunction of the front-ECU
  • Damaged harness wires and connectors

DIAGNOSIS PROCEDURE

STEP 1. ECU check by using the SWS monitor.
Check that the power supply and earth lines to the column switch (column-ECU) and the front-ECU and the SWS communication lines are normal.

  • Ignition switch: OFF
ECUS TO BE CHECKED
  • COLUMN ECU
  • FRONT ECU
OK: "OK" are displayed for all the items

Q. Is the check result normal?
YES ("OK" are displayed for all the items) : Go to Step 2.
NO ("NG" is displayed on the "COLUMN ECU" menu) : Refer to GROUP 54C - Trouble Symptom Chart .
NO ("NG" is displayed on the "FRONT ECU" menu) : Refer to GROUP 54C - Trouble Symptom Chart .

STEP 2. Function diagnosis by using the SWS monitor.
Check the SWS communication signal, which are related to the low-beam headlamps.
<Selected item> LIGHTING - HEADLAMP LO
  • Ignition switch: ON
  • Lighting switch: HEAD
Item No.
 Item name
 Normal condition
Item 00
 HEADLAMP SW
 ON
Item 03
 PASSING SW
 OFF
Item 30
 IG SW(IG1)
 ON
Item 35
 HD AUTO-CUT
 OFF
Item 70
 FRONT ECU ACK
 NORMAL ACK
OK: Normal conditions are displayed for all the items

Q. Is the check result normal?
YES (Normal conditions are displayed for all the items) : Go to Step 3.
NO (Normal condition is not displayed for item No.00 or 03) : Refer to ETACS - Input Signal Chart .
NO (Normal condition is not displayed for item No.30) : Refer to ETACS - Input Signal Chart .
NO (Normal condition is not displayed for item No.35) : Refer to Inspection Procedure 5 "The headlamp automatic-shutdown function does not work normally .
NO (Normal condition is not displayed for item No.70) : Replace the front-ECU.

STEP 3. Connector check: A-08X front-ECU connector

Q. Is the check result normal?
Go to Step 4.
Repair the defective connector.

STEP 4. Voltage measurement at A-08X front-ECU connector.
(1)Remove the front-ECU, and measure at the relay box side.
(2)Voltage between A-08X front-ECU connector terminal Nos.3, 4, 5 and body earth
OK: System voltage

Q. Is the check result normal?
Go to Step 6.
Go to Step 5.

STEP 5. Check the wiring harness between A-08X front-ECU connector terminal Nos.3, 4, 5 and the battery.

  • Check the power supply line for open circuit.

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Repair the wiring harness.

STEP 6. Retest the system.
Check that the low-beam headlamps illuminate normally.

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the front-ECU.