Code No. P1603: Battery Backup Circuit Malfunction

OPERATION

Power is directly supplied to the engine-ECU (terminal No. 58) from the battery.

FUNCTION

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

TROUBLE JUDGMENT

Check Conditions

After engine starting sequence is completed.
Battery positive voltage is 10 V or higher.

Judgment Criterion

Battery backup line voltage is 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 of P1603 output?

	Go to Step 2 .

	Check end.

STEP 2. Perform voltage measurement at D-244 engine-ECU <M/T> connector or D-214 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-03 <L.H. drive vehicles> or D-137 <R.H. drive vehicles> and repair if necessary. If intermediate connector is normal, check and repair harness between the battery and D-244 (terminal No. 58) engine-ECU <M/T> connector or D-214 (terminal No. 58) engine-A/T-ECU <A/T> connector. Check power supply line for open/short circuit.

STEP 3. Connector check: D-244 engine-ECU <M/T> connector or D-214 engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

	Go to Step 4 .

	Repair or replace the connector.

STEP 4. Check harness between the battery and D-244 (terminal No. 58) engine-ECU <M/T> connector or D-214 (terminal No. 58) engine-A/T-ECU <A/T> connector.

note

Before checking harness, check intermediate connector A-03 <L.H. drive vehicles> or D-137 <R.H. drive vehicles>, 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 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 ).