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DTC P0622: Generator FR Terminal Circuit Malfunction
 
 
 
 
CIRCUIT OPERATION
  • The ECM terminal ALTF apply a battery positive voltage into the generator FR terminal via resistance inside the unit.
 
 
TECHNICAL DESCRIPTION
  • When the generator field coils are controlled, the generator FR terminal inputs signal to the ECM.
  • The ECM detects the generator output with the input signal, and controls the idle air control motor according to the generator output.
 
 
DTC SET CONDITIONS
Check Conditions
  • Ignition switch is "ON" position.
  • While engine is running.
Judgment Criteria
  • The FR-terminal duty ratio is 0 percent for 20 seconds.
 
 
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 area: )
  • Generator failed.
  • Connector damage.
  • Harness damage.
  • ECM failed.

 
 
DIAGNOSIS
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)
  • MB992110: Power Plant ECU Check Harness
STEP 1. Measure the voltage at ECM connector by using power plant ECU check harness special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2) Start the engine and run at idle.
(3) Measure the voltage between terminal ALTF and ground.
noteVehicle for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks.
  1. Engine: warming up
  2. Radiator fan: stopped
  3. Headlight switch: OFF to ON
  4. Rear defogger switch: OFF to ON
  5. Stoplight switch: OFF to ON
  • Voltage should be drop.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Did the measured voltage drop?
Go to Step 2.
Go to Step 3.
 
STEP 2. Using scan tool (M.U.T.-III), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(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 DTC P0622 stored?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 6.
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 3. Measure the voltage at generator harness side connector.
(1) Disconnect the generator connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal ALTF line and ground.
  • Voltage should measure battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 5.
Go to Step 4.
 
STEP 4. Check of open circuit in ALTF line between generator connector and ECM connector.
Is the harness wire in good condition?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 6.
Repair it. Then go to Step 6.
 
STEP 5. Check of harness damage in ALTF line between generator connector and ECM connector.
Is the harness wire in good condition?
Replace the generator. Then go to Step 6.
Repair it. Then go to Step 6.
 
STEP 6. Using scan tool (M.U.T.-III), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T.-III) 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.
Is DTC P0622 stored?
Retry the troubleshooting.
The inspection is complete.