Code No.C1541 Power supply voltage abnormality (low voltage)

caution

If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

Power is supplied to the electric power steering-ECU from the battery or the ignition switch.

FUNCTION

To control the steering gear and linkage assembly, the battery voltage is supplied to the electric power steering-ECU for energisation.

TROUBLE JUDGEMENT

Check Conditions

The ETACS power supply circuit system diagnosis code is not set.

Judgement Criterion

The power supply voltage is less than 9.0 V.
The power supply monitor voltage does not meet a predetermined voltage stored in the microcomputer, and the microcomputer determines that there is a problem in the power supply system.

Fail Safe, Back Up Function

The electric power steering-ECU tapers the motor control and illuminates the electric power steering warning display, then sets the diagnosis code No. C1541.

PROBABLE CAUSES

Malfunction of CAN bus line
Defective battery
Charging system failed
Defective harness wire(s) or connector(s)

Short or open circuit between the electric power steering-ECU, the ETACS-ECU and the fusible link or loose connector contact
Open circuit between the body earth and the electric power steering-ECU or loose connector contact

Malfunction of the ETACS-ECU
Malfunction of the electric power steering-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics

Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 3.

	Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

(1)Erase the diagnosis code.

(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.

(3)Check if the diagnosis code is set.

Q. Is the diagnosis codes C1541 set?

	Go to Step 3.

	This diagnosis is complete.

STEP 3. Check the battery voltage.

Start the engine and measure the battery voltage (Refer to GROUP 54A - Battery Test

Q. Is the check result normal?

	Go to Step 4.

	Check the battery and repair if necessary (Refer to GROUP 54A - Charging System , GROUP 54A - Removal and Installation ). Then go to Step 11.

STEP 4. Check the charging system.

Start the engine and measure the charging system (Refer to GROUP 16 - Charging System

Q. Is the check result normal?

	Go to Step 5.

	Check the charging system and repair if necessary (Refer to GROUP 16 - Alternator Assembly ).Then go to Step 11.

STEP 5. Check the following connector.

Check the connectors below for improper engagement, terminal damage or terminal drawn in the connector case.

C-113 and C-114-1 electric power steering-ECU connector
C-309 and C-317 ETACS-ECU connector
C-128 intermediate connector
No.34 and No.35 fusible link
No.18 body earth point

Q. Is the connectors and terminals in good condition?

	Go to Step 6.

	Repair the defective connector(s) or terminal(s). Then go to Step 11.

STEP 6. Wiring harness check

(1)Check the wiring harness between the C-113 electric power steering-ECU connector terminal No.11 and the fusible link No.35 for damage or other problem .

(2)Check the wiring harness between the C-114 electric power steering-ECU connector terminal No.1, the C-128 intermediate connector terminal No.19 and the C-317 ETACS-ECU connector terminal No.5 for damage or other problem .

(3)Check the wiring harness between the C-309 ETACS-ECU connector terminal No.1 and the fusible link No.34 for damage or other problem .

(4)Check the wiring harness between the C-113 electric power steering-ECU connector terminal No.12 and the body earth point No.18 for damage or other problem .

Q. Is the wiring harness in good condition?

	Go to Step 7.

	Repair the defective wiring harness. Then go to Step 11.

STEP 7. Voltage measurement at the ETACS-ECU connector

(1) Measure the ETACS-ECU voltage without disconnecting the connector (by backprobing).
(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3)Measure the voltage between the C-309 ETACS-ECU connector terminal No.1 and the C-317 ETACS-ECU connector terminal No.5.
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 8.

Check the fusible link or the ETACS-ECU and repair if necessary(Refer to GROUP 54A-ETACS

).Then go to Step 11.

STEP 8. Voltage measurement at the electric power steering-ECU connector

(1) Measure the electric power steering-ECU voltage without disconnecting the connector (by backprobing).
(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3)Measure the voltage between the C-114 electric power steering-ECU connector terminal No.1 and the C-113 electric power steering-ECU connector terminal No.12.
OK: Approximately battery voltage
(4)Measure the voltage between the C-113 electric power steering-ECU connector terminals No.11 and No.12.
OK: Approximately battery voltage

Q. Is the check result normal?

Go to Step 9.

Check the fusible link or the ETACS-ECU and repair if necessary(Refer to GROUP 54A-ETACS

).Then go to Step 11.

STEP 9. M.U.T.-III data list

Check the following service data

Item No. 22: Power relay voltage

Item No. 23: Ignition voltage

Q. Is the check result normal?

	Go to Step 11.

	Go to Step 10.

STEP 10. Check whether the diagnosis code is reset.

(1)Erase the diagnosis code.

(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.

(3)Check if the diagnosis code is set.

Q. Is the diagnosis codes C1541 set?

	Replace the electric power steering-ECU (Refer to ).Then go to Step 11.

	Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 11. Check whether the diagnosis code is reset.

(1)Erase the diagnosis code.

(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.

(3)Check if the diagnosis code is set.

Q. Is the diagnosis codes C1541 set?

	Return to Step 1.

	This diagnosis is complete.