Code No. P1603: Battery Backup Circuit Malfunction

OPERATION

Power is directly supplied to the engine-ECU (terminal No. 82) from the battery.

FUNCTION

The engine-ECU checks the open circuit of 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 and damage in battery backup line circuit or loose connector contact
Failed engine-ECU

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 A-35 engine-ECU connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 82 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 3 .

Check power supply line for open/short circuit.

STEP 3. Check harness between battery and A-35 (terminal No. 82) engine-ECU connector.

note

Before checking harness, check intermediate connector B-208 and B-212, and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

Go to Step 4 .

STEP 4. Connector check: A-35 engine-ECU connector

Q. Is the check result normal?

Go to Step 5 .

Repair or replace the connector.

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

Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?

	Replace the engine-ECU then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).

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