P0620

DTC P0620: Generator Control Circuit

CIRCUIT OPERATION

- When the ignition switch is turned ON, the current should be supplied from the ECM (terminal No. 62) to the generator (terminal No. 3). When the engine starts under those conditions, the generator should generate currents. The generated voltage is applied to the ECM (terminal No. 62) from the generator (terminal No. 3). This allows the ECM to detect that the electrical generation begins.
- The ECM (terminal No. 60) controls the generator output voltage by turning the power transistor in the unit ON/OFF according to the electrical load.

TECHNICAL DESCRIPTION

The ECM Compares the battery voltage with the voltage generated from the generator to check whether the electrical generation is normal.

DESCRIPTION OF MONITOR METHOD

The difference exceeds the specified value between the target generation voltage and the battery backup voltage.

DTC SET CONDITION

Check Conditions

- Ignition switch is "ON" position.
- The engine speed is 600 r/min or more.
- The battery backup voltage is 13.5 volts or more.
- The G-terminal duty ratio is 80 percent or less and the malfunction of DTC P0622 is not detected.
Judgement Criterion

- For 30 seconds, the final target generation voltage subtracted from the battery backup voltage equals 0.8 volt or more.
or

- For 30 seconds, the battery backup voltage subtracted from the final target generation voltage equals 1.3 volts or more.

PROBABLE CAUSES

- Battery failed.
- Drive belt failed.
- Open/shorted generator G-terminal circuit, or connector damage.
- Open/shorted generator L-terminal circuit, or connector damage.
- Battery backup circuit harness damage or connector damage.
- Generator failed.
- ECM failed.

DIAGNOSIS PROCEDURE

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB992110: Power Plant ECU Check Harness

STEP 1. Checking engine start conditions

- Check whether the user uses the booster cable to start the engine.

NOTE:
This diagnostic trouble code (DTC) can be output due to the battery voltage drop.

Q. Have you ever used the booster cable to start the engine?

YES Delete the DTC and check end.
NO Go to Step 2.
STEP 2. Check battery itself

- Check battery itself Battery Check ).

Q. Is the check result normal?

YES Go to Step 3.
NO Repair. Then go to Step 13.
STEP 3. Check drive belt tension

- Check the drive belt tension [ Testing and Inspection].

Q. Is the check result normal?

YES Go to Step 4.
NO Replace the drive belt. Then go to Step 13.
STEP 4. Check harness connector B-108 at ECM for damage.

Q. Is the harness connector in good condition?

YES Go to Step 5.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 13.
STEP 5. Check harness connector B-15 at generator for damage.

Q. Is the harness connector in good condition?

YES Go to Step 6.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 13.
STEP 6. Check for open circuit, short circuit to ground and damage between generator connector B-15 (terminal No. 1) and ECM connector B-108 (terminal No. 60).

Q. Is the harness wire in good condition?

YES Go to Step 7.
NO Repair it. Then go to Step 13.
STEP 7. Check for open circuit, short circuit to ground and damage between generator connector B-15 (terminal No. 3) and ECM connector B-108 (terminal No. 62).

Q. Is the harness wire in good condition?

YES Go to Step 8.
NO Repair it. Then go to Step 13.
STEP 8. Check harness connector B-109 at ECM for damage.

Q. Is the harness connector in good condition?

YES Go to Step 9.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 13.
STEP 9. Check for damage between battery and ECM connector B-109 (terminal No. 104).

Q. Is the harness wire in good condition?

YES Go to Step 10.
NO Repair it. Then go to Step 13.
STEP 10. Using scan tool MB991958, read the diagnostic trouble code
(DTC).

(1)Connect scan tool MB991958 to the data link connector.
(2)Start the engine and run at idle.
(3)After the DTC has been deleted, read the DTC again.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC P0620 set?

YES Go to Step 11.

NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

STEP 11. Replace the drive belt.

(1)Replace the drive belt.

(2)Connect scan tool MB991958 to the data link connector.

(3)Start the engine and run at idle.

(4)After the DTC has been deleted, read the DTC again.

(5)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC P0620 set?

YES Go to Step 12.
NO The inspection is complete.
STEP 12. Replace the generator.

(1)Replace the generator.

(2)Connect scan tool MB991958 to the data link connector.

(3)Start the engine and run at idle.

(4)After the DTC has been deleted, read the DTC again.

(5)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC P0620 set?

YES Replace the ECM (Refer to, Removal and Installation Removal and Replacement).
Then go to Step 13.
NO The inspection is complete.
STEP 13. Using scan tool MB991958, read the diagnostic trouble code
(DTC).