Code No. P1603: Battery Backup Circuit Malfunction

FUNCTION

The engine-A/T-ECU (terminal No. 58) checks open circuit in the battery backup line.

TROUBLE JUDGMENT

Check Conditions

After engine starts.
Battery voltage is more than 10 V.

Judgment Criterion

Battery backup line voltage is less than 6 V for 2 seconds.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

note

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 of P1603 set?

	Go to Step 2 .

	Check end.

STEP 2. Connector check: D-214 engine-A/T-ECU connector

Q. Is the check result normal?

	Go to Step 3 .

	Repair or replace the connector.

STEP 3. Perform voltage measurement at D-214 engine-A/T-ECU 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 4 .

	Check intermediate connector A-03¹ or D-137² and repair if necessary. If intermediate connector is normal, check and repair harness between the battery and D-214 (terminal No. 58) engine-A/T-ECU connector. Check power supply line for open/short circuit.

STEP 4. Check harness between the battery and D-214 (terminal No. 58) engine-A/T-ECU connector.

note

Before checking harness, check intermediate connector A-03*¹ or D-137*², and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 5 .

	Repair the damaged harness wire.

STEP 5. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?

	Replace the engine-A/T-ECU.

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