Code No. P0622: Alternator FR Terminal System
OPERATION
- The energised state of the alternator field coil is inputted from the alternator connector terminal to the engine-ECU connector terminal ALTF.
FUNCTION
- A signal of the power supply duty ratio for the alternator field coil is inputted to the engine-ECU.
- In response to the signal, the engine-ECU detects the alternator output current and controls the idling speed according to the output current (electric load).
TROUBLE JUDGEMENT
Check Condition
- While the engine is running
Judgement Criterion
- Input voltage from the alternator FR terminal is approximately battery positive voltage for 20 seconds.
FAIL-SAFE AND BACKUP FUNCTION
PROBABLE CAUSES
- Failed alternator
- Open circuit or harness damage in alternator circuit or loose connector contact
- Failed engine-ECU
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STEP 1. Voltage measurement at alternator connector (ALTF 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 (ALTF line) and body earth.
OK: System voltage
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Q.
Is the check result normal?
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 Go to Step 4.
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 Go to Step 2.
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STEP 2. Check of open circuit in ALTF line between alternator connector and engine-ECU connector.
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the connector(s) or wiring harness.
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STEP 3. M.U.T.-III diagnosis code
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- Reconfirmation of diagnosis code.
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Q.
Is diagnosis code set?
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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 4. Check of damage in ALTF line between alternator connector and engine-ECU 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. Voltage measurement at engine-ECU connector (ALTF 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)Radiator fan: Not operated
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(5)Check the voltage between the engine-ECU connector (ALTF terminal) and body earth.
OK: Voltage decreases when the headlamps are extinguished → illuminated.
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Q.
Is the check result normal?
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Go to Step 3.
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Replace the alternator.
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