P0622

DTC P0622: Generator FR Terminal Circuit Malfunction














CIRCUIT OPERATION

- The ECM (terminal No. 61) apply a battery positive 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.

- Connector damage.

- Harness 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-10 at ECM connector for damage.

Q. Is the harness connector in good condition?

YES Go to Step 2.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 8.
STEP 2. Measure the voltage at ECM connector B-10 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.
NOTE:
Vehicles 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.

Q. Did the measured voltage drop?

YES Go to Step 3.

NO 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?

YES Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 8.

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

STEP 4. Check harness connector B-118 at generator connector 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 8.
STEP 5. Measure the voltage at generator harness side connector B-118.

(1)Disconnect the connector B-118 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?

YES Go to Step 7.

NO Go to Step 6.

STEP 6. Check for open circuit and short circuit to ground between generator connector B-118 and ECM connector B-10.





(1)Disconnect the connector B-118 and B-10 measure at the harness side.
(2)Measure the resistance between connector B-118 (terminal No. 4) and connector B-10
(terminal No. 61).

- Should be less than 2 ohms.





(3)Check for the continuity between connector B-118 (terminal No. 4) and ground.

- Not continuity.

Q. Is the harness wire in good condition?

YES Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 8.

NO Repair it. Then go to Step 8.

STEP 7. Check for harness damage between generator connector B-118 and ECM connector B-10.





(1)Disconnect the connector B-118 and B-10 measure at the harness side.
(2)Measure the resistance between connector B-118 (terminal No. 4) and connector B-10
(terminal No. 61).

- Should be less than 2 ohms.

Q. Is the measured resistance less than 2 ohms?

YES Replace the generator. Then go to Step 8.

NO Repair it. Then go to Step 8.

STEP 8. Using scan tool MB991958, read the diagnostic trouble code
(DTC).

(1)Start the engine and run at idle.

(2)Read the DTC.

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

Q. Is DTC P0622 set?

YES Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM].
NO The inspection is complete.