Inspection Procedure 14: Battery Rundown
OPERATION
- The exciting currents of the alternator field coil are input into the engine-ECU connector terminal ALTL from the alternator connector terminal.
- The electric generating capacity of the alternator connector terminal is restricted according to the signal from the engine-ECU connector terminal ALTG.
COMMENTS ON TROUBLE SYMPTOM
- The failure could possibly be caused by the failed alternator, defective alternator control system and so on.
PROBABLE CAUSES
- Failed battery
- Open/short circuit or harness damage in alternator L terminal circuit
- Short circuit in alternator G terminal
- Failed alternator
- Failed engine-ECU
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- Check battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery Test
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Q.
Is the check result normal?
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 Go to Step 2.
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 Replace the battery.
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STEP 2. M.U.T.-III diagnosis code
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Q.
Is diagnosis code set?
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Inspection chart for diagnosis code (Refer to ).
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Go to Step 3.
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STEP 3. Voltage measurement at alternator connector (ALTL line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Check the voltage between the alternator connector (ALTL line) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 6.
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Go to Step 4.
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STEP 4. Check of open circuit and short to earth in ALTL line between engine-ECU connector and alternator connector.
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the connector(s) or wiring harness.
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STEP 5. Check the trouble symptom.
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Q.
Does the trouble symptom persist?
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Replace the engine-ECU.
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
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STEP 6. Check of damage in ALTL line between engine-ECU connector and alternator connector.
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Q.
Is the check result normal?
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Go to Step 7.
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Repair the connector(s) or wiring harness.
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STEP 7. Voltage measurement at alternator connector (ALTG line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Connect special tool Test Harness (MB991658) to all terminals except the terminal output line.
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(4)Check the voltage between the alternator connector (ALTG line) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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Go to Step 8.
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Replace the alternator.
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STEP 8. Check of short to earth in ALTG line between engine-ECU connector and alternator connector.
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Q.
Is the check result normal?
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Go to Step 9.
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Repair the connector(s) or wiring harness.
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STEP 9. Voltage measurement at engine-ECU connector (ALTG terminal).
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(1)Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992291) to measure at connector for inspection.
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(2)Engine: Idle operation after warm-up
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(4)Cooling fan: Not operated
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(5)Check the voltage between the engine-ECU connector (ALTG terminal) and body earth.
OK: The voltage increases when the headlamp switch and the rear window defogger switch are turned ON from OFF
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
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Go to Step 5.
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