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DTC P0620: Generator Control Circuit
 
 
 
 
CIRCUIT OPERATION
  • When the ignition switch is turned ON, the current should be supplied from the ECM terminal ALTL to the generator. When the engine starts under those conditions, the generator should generate currents. The generated voltage is applied to the ECM terminal ALTL from the generator. This allows the ECM to detect that the electrical generation begins.
  • The ECM terminal ALTG 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 10.2 percent or more and 89.8 percent or less.
Judgment Criteria
  • For 30 seconds, the final target generation voltage subtracted from the battery backup voltage equals 0.8 volt or more.
Check Conditions
  • Ignition switch is "ON" position.
  • The engine speed is 600 r/min or more.
  • The FR-terminal duty ratio is 80 percent or less and the malfunction of DTC P0622 is not detected.
  • The G-terminal duty ratio is 10.2 percent or more and 89.8 percent or less.
Judgment Criteria
  • For 30 seconds, the battery backup voltage subtracted from the final target generation voltage equals 1.3 volts or more.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Prohibits generator output suppression control against current consumers (operates as a normal generator).
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be stored are:)
  • 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.
 
 
 
DIAGNOSTIC PROCEDURE
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Checking engine start conditions
  • Check whether the user uses the booster cable to start the engine.
noteThis diagnostic trouble code (DTC) can be output due to the battery voltage drop.
Have you ever used the booster cable to start the engine?
Delete the DTC and check end.
Go to Step 2.
 
STEP 2. Check battery itself
  • Check battery itself (Refer to GROUP 54A, Battery - On-vehicle Service - Battery Test ).
Is the check result normal?
Go to Step 3.
Repair. Then go to Step 10.
 
STEP 3. Check drive belt tension
  • Check the drive belt tension [Refer to GROUP 00 - Maintenance Service - Drive Belt (For Water Pump and Generator) (Check Condition) ].
Is the check result normal?
Go to Step 4.
Replace the drive belt. Then go to Step 10.
 
STEP 4. Check of short to ground, open circuit and harness damage in ALTG line between generator connector and ECM connector.
Is the harness wire in good condition?
Go to Step 5.
Repair it. Then go to Step 10.
 
STEP 5. Check of short to ground, open circuit and harness damage in ALTL line between generator connector and ECM connector.
Is the harness wire in good condition?
Go to Step 6.
Repair it. Then go to Step 10.
 
STEP 6. Check of harness damage in BACK line between battery and ECM connector.
Is the harness wire in good condition?
Go to Step 7.
Repair it. Then go to Step 10.
 
STEP 7. Using scan tool (M.U.T.-III), read the diagnostic trouble code (DTC).
(1) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(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.
Is the DTC P0620 stored?
Go to Step 8.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/ Inspection Service Points - How to Cope with Intermittent Malfunctions .
 
STEP 8. Replace the drive belt.
(1) Replace the drive belt.
(2) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(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.
Is the DTC P0620 stored?
Go to Step 9.
The inspection is complete.
 
STEP 9. Replace the generator.
(1) Replace the generator.
(2) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(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.
Is the DTC P0620 stored?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 10.
The inspection is complete.
 
STEP 10. Using scan tool (M.U.T.-III), read the diagnostic trouble code (DTC).
(1) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(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.
Is the DTC P0620 stored?
Retry the troubleshooting.
The inspection is complete.