P0622

DTC P0622: Generator FR Terminal Circuit Malfunction

CIRCUIT OPERATION

- The ECM[ M/T] or the PCM[ A/T] (terminal No. 131) 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[ M/T] or the PCM[ A/T].
- The ECM[ M/T] or the PCM[ A/T] 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 approximately battery positive voltage for 20 seconds.

TROUBLESHOOTING HINTS (The most likely causes for this code to be set area:)

- Generator failed.
- Open or shorted circuit in generator FR terminal circuit, harness damage or connector damage.
- ECM failed.[ M/T]
- PCM failed.[ A/T]

DIAGNOSIS

Required Special Tools:

- MB991958: Scan tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB991923: Power Plant ECU Check Harness

STEP 1. Check harness connector B-22 at ECM [M/T]
or PCM [A/T]
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 [M/T]
or PCM [A/T]
connector B-22 by using power plant ECU check harness special tool MB991923.

(1)Disconnect all ECM [M/T]
connectors or PCM [A/T]
connectors.
Connect the power plant ECU check harness special tool MB991923 between the separated connectors.
(2)Start the engine and run at idle.

(3)Measure the voltage between terminal No. 131 and ground.
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.

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 or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Encrypted Code Registration Criteria Table.
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-120 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-120.

(1)Disconnect the connector B-120 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-120 (terminal No. 4) and ECM [M/T]
or PCM [A/T]
connector B-22 (terminal No. 131).

Q. Is the harness wire in good condition?

YES Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Encrypted Code Registration Criteria Table.
Then go to Step 8.

NO Repair it. Then go to Step 8.

STEP 7. Check for harness damage between generator connector B-120
(terminal No. 4) and ECM [M/T]
or PCM [A/T]
connector B-22 (terminal No. 131).

Q. Is the harness wire in good condition?

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).