[Previous][Next]
DTC P0622: Generator FR Terminal Circuit Malfunction

 
 
 
 
CIRCUIT OPERATION
  • The ECM (terminal No. 61) apply a battery voltage into the generator FR terminal No. 4 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 throttle actuator control motor according to the generator output.
 
 
DTC SET CONDITIONS
Check Condition
  • Engine speed is more than 50 r/min.
Judgment Criterion
  • Input voltage from the generator FR terminal is battery positive voltage 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 set area:)
  • Generator failed.
  • Open circuit in generator FR terminal circuit, harness damage or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
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. Check harness connector B-26 at ECM for damage.
Is the harness connector in good condition?
Go to Step 2.
Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 8.
 
STEP 2. Measure the output voltage at ECM connector B-26 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 No. 61 and ground.
noteVehicles 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 3.
Go to Step 4.
 
STEP 3. Using scan tool MB991958, read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(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.
Is DTC P0622 set?
Replace the ECM (Refer to, Removal and Installation ). Then 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 4. Check harness connector B-117 at generator for damage.
Is the harness connector in good condition?
Go to Step 5.
Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 8.
 
STEP 5. Measure the power supply voltage at generator harness side connector B-117.
(1) Disconnect the connector B-117 and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 4 and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 7.
Go to Step 6.
 
STEP 6. Check for open circuit between generator connector B-117 (terminal No. 4) and ECM connector B-26 (terminal No. 61).
Is the harness wire in good condition?
Replace the ECM (Refer to, Removal and Installation ). Then go to Step 8.
Repair it. Then go to Step 8.
 
STEP 7. Check for harness damage between generator connector B-117 (terminal No. 4) and ECM connector B-26 (terminal No. 61).
Is the harness wire in good condition?
Replace the generator. Then go to Step 8.
Repair it. Then go to Step 8.
 
STEP 8. Using scan tool MB991958, read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(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.
Is DTC P0622 set?
Retry the troubleshooting.
The inspection is complete.