Code No. P0622: Alternator FR Terminal System

OPERATION

The energized 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 JUDGMENT

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

The AS&G control is prohibited.

PROBABLE CAUSES

Failed alternator
Open circuit or harness damage in alternator circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Perform voltage measurement at alternator connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal engine-ECU ALTF line and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 4.

	Go to Step 2.

STEP 2. Check harness between alternator connector terminal and engine-ECU connector terminal ALTF.

Check output line for open circuit.

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 3. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code set?

	Replace the engine-ECU.

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

STEP 4. Check harness between alternator connector terminal and engine-ECU connector terminal ALTF.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 5. Perform voltage measurement at engine-ECU connector.

Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992291) to measure at connector for inspection.
Engine: Idle operation after warm-up
Transmission: Neutral
Radiator fan: Not operated
Voltage between terminal ALTF and body earth.

OK: Voltage decreases when the headlamps are extinguished → illuminated.

Q. Is the check result normal?

	Go to Step 3.

	Replace the alternator.