Code No. P1603: Battery Backup Line System

OPERATION

Power is directly supplied to the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 58) from the battery.

FUNCTION

The engine-ECU <M/T> or engine-A/T-ECU <A/T> is check the open circuit of battery backup line.

TROUBLE JUDGMENT

Check Conditions

After the engine has started up.
Battery positive voltage is 10 V or higher.

Judgment Criterion

The battery backup line voltage 6 V or lower for 2 seconds.

PROBABLE CAUSES

Open/short circuit in battery backup line circuit or loose connector contact
Failed engine-ECU <M/T> or engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Temporarily place the ignition switch in "LOCK" (OFF) position, and 10 seconds after that, place it in "ON" position again.

Q. Is the diagnosis code P1603 set?

	Go to Step 2 .

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 2. Perform voltage measurement at C-155 engine-ECU <M/T> connector or C-155 engine-A/T-ECU <A/T> connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 58 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 3 .

	Check intermediate connector A-115, and repair if necessary. If intermediate connector is normal, check and repair harness between battery and C-155 (terminal No. 58) engine-ECU <M/T> connector or C-155 (terminal No. 58) engine-A/T-ECU <A/T> connector. Check power supply line for open/short circuit.

STEP 3. Connector check: C-155 engine-ECU <M/T> connector or C-155 engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

	Go to Step 4 .

	Repair or replace the connector.

STEP 4. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?

	Replace the engine-ECU <M/T> or engine-A/T-ECU <A/T>.

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).