Inspection Procedure 17: Engine-ECU Battery Back-up System

OPERATION

Backup power source is directly supplied to an engine-ECU from a battery.

PROBABLE CAUSES

Damaged harness (Open circuit between engine-ECU and relay box)
Damaged connector (Engine-ECU connector)
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check battery voltage.

Measure battery voltage during cranking.

OK: 8 V or more

Q. Is the check result normal?

	Go to Step 2 .

	Check battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery test ).

STEP 2. Perform voltage measurement at C-103 engine-ECU connector.

Disconnect connector, and measure at harness side.
Voltage between terminal No. 101 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 5 .

Go to Step 3 .

STEP 3. Connector check: C-103 engine-ECU connector and A-115 intermediate connector.

Q. Are the check results normal?

Go to Step 4 .

Repair or replace.

STEP 4. Check for open circuit between C-103 (terminal No. 101) engine-ECU connector and A-115 (terminal No. 3) intermediate connector.

Disconnect connector.

Q. Is the check result normal?

Go to Step 5 .

Repair the harness wire.

STEP 5. Check the trouble symptoms.

Q. Does trouble symptom persist?

	Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

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