Code No.B1728, B1729: Abnormal voltage at ETACS-ECU power supply




COMMENTS ON TROUBLE SYMPTOM


If the voltage at the ETACS-ECU is excessively lower than system voltage, the ETACS-ECU sets diagnosis code No.B1728. If the voltage is excessively higher than system voltage, the ETACS-ECU sets diagnosis code No.B1729.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. Power supply fuse check

Q. Is the fuse in good condition?
Go to Step 2.
Replace the power supply fuse, and then go to Step 9.

STEP 2. Battery check
Refer to GROUP 54A - Battery Test .

Q. Is the battery in good condition?
Go to Step 3.
Charge or replace the battery.

STEP 3. Charging system check
Refer to GROUP 16 - Charging System .

Q. Is the charging system in good condition?
Go to Step 4.
Repair or replace the charging system component(s).

STEP 4. M.U.T.-III data list
Check the power supply voltage of the ETACS-ECU.
(1)Turn the ignition switch to the "LOCK" (OFF) position
Item No.
 Item name
 Normal condition
32
 Battery voltage (battery)
 System voltage
OK: Normal condition is displayed.
(2)Turn the ignition switch to the "ON" position
Item No.
 Item name
 Normal condition
31
 Battery voltage (IG1)
 System voltage
OK: Normal condition is displayed.

Q. Is the check result normal?
YES <All the signals are received normally.> : Go to Step 9.
NO <Battery voltage (battery) is abnormal> : Go to Step 5.
NO <Battery voltage (IG1) is abnormal> : Go to Step 7.

STEP 5. Connector check: B-234 ETACS-ECU connector


Q. Is the check result normal?

Go to Step 6.

Repair the connector, and then go to Step 9.

STEP 6. Check the wiring harness between B-234 ETACS-ECU connector terminal No.20 and the fusible link (1).





note Prior to the wiring harness inspection, check the junction block connector B-208 and repair if necessary.

  • Check the power supply line from the fusible link (1) for open circuit.

Q. 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 ). Go to Step 9.

Repair the wiring harness, and then go to Step 9.

STEP 7. Connector check: B-233 ETACS-ECU connector


Q. Is the check result normal?

Go to Step 8.

Repair the connector, and then go to Step 9.

STEP 8. Check the wiring harness between B-233 ETACS-ECU connector terminal No.52 and the ignition switch (IG1).




note Prior to the wiring harness inspection, check the joint connector B-26, junction block connectors B-229, B-231, and repair if necessary.

  • Check the power supply line to the ignition switch (IG1) for open circuit.

Q. Is the check result normal?

Perform troubleshooting for ignition switch. Refer to GROUP 54A - Ignition switch . Go to Step 9.

Repair the wiring harness, and then go to Step 9.

STEP 9. Check whether the diagnosis code is reset.
Check if diagnosis code No.B1728 or B1729 is set.

Q. Is the diagnosis code set?
Replace the ETACS-ECU. Then perform the variant coding and write the VIN data (Refer to GROUP 00, Precautions Before Service - How to Perform Variant Coding ).
The procedure is complete.