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 idle air control motor according to the generator output.

DTC SET CONDITIONS

Check Condition

Engine speed is higher than 50 r/min.

Judgement Criterion

Input voltage from the generator FR terminal has continued to be battery positive voltage for 20 seconds.

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-108 at ECM connector for damage.

Q. 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 voltage at ECM connector B-108 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 under the following driving.

note

Vehicle for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks.

Engine: warming up
Radiator fan: stopped
Headlight switch: OFF to ON
Rear defogger switch: OFF to ON
Stoplight switch: OFF to ON

Voltage should be drop.

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

Q. 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).

caution

To 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)Read the DTC.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC P0622 set?

Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS>

or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM>

. 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-15 at generator connector for damage.

Q. 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 voltage at generator harness side connector B-15.

(1)Disconnect the connector B-15 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 measure battery positive voltage.

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

Q. Is battery positive voltage (approximately 12 volts) present?

Go to Step 7.

Go to Step 6.

STEP 6. Check for open circuit and short circuit to ground between generator connector B-15 (terminal No. 4) and ECM connector B-108 (terminal No. 61).

Q. Is the harness wire in good condition?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS> or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 8.

	Repair it. Then go to Step 8.

STEP 7. Check for harness damage between generator connector B-15 (terminal No. 4) and ECM connector B-108 (terminal No. 61).

Q. 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).

caution

To 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)Read the DTC.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC P0622 set?

Retry the troubleshooting.

The inspection is complete.