OPERATION
- Power is directly supplied to the engine-A/T-ECU (terminal No. 58) from the battery.
FUNCTION
- The engine-A/T-ECU is check 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.
- Ignition switch is "ON" position
Judgment Criterion
- Battery backup line voltage is 6 V or lower for 2 seconds.
PROBABLE CAUSE
- Open/short circuit in battery backup line circuit or loose connector contact
- Failed engine-A/T-ECU
DIAGNOSIS PROCEDURE
STEP 1. MUT-II/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?
YES:
Go to Step 2 
.NO: Intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/Inspection Service Points
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- 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?
YES:
Go to Step 3 .NO:
- Check intermediate connector A-14, and repair if necessary. If intermediate connector is normal, check and repair harness between battery and C-135 (terminal No. 58) engine-A/T-ECU connector.
- Check power supply line for open/short circuit.
- Check earthing line for damage.
Q: Is the check result normal?
YES:
Go to Step 4 .NO:
- Repair.
Q: Is the check result normal?
YES:
Go to Step 5 .NO: Repair.