Fix P0622: Mechanic’s solutions that WORKED

The P0622: Generator Field “F” Control Circuit Malfunction highlights a malfunction in the generator field control circuit, which plays a crucial role in regulating the alternator’s output. This circuit, controlled by the PCM, ensures the alternator provides the right amount of power to charge the vehicle’s battery and power electrical systems. A fault in this circuit can lead to irregular charging, potentially causing battery drain or electrical malfunctions.

P0622 quick overview

Meaning	P0622: Generator Field “F” Control Circuit Malfunction
Is it serious?	This code indicates an issue with the vehicle’s charging system, which can lead to battery drain and potentially serious electrical problems if not addressed promptly.
Possible causes	– Faulty or incorrect alternator – Damaged or corroded wiring to the alternator – Problems with the alternator’s field control circuit – PCM (Powertrain Control Module) issues – Poor grounding of the charging system components
How to diagnose?	Inspect Alternator: Verify if the alternator installed is correct and functioning properly. Check Wiring: Examine wiring, particularly at the alternator and PCM, for any damage or corrosion. Test Field Control Circuit: Evaluate the field control circuit from the alternator to the PCM for continuity and signal integrity. Evaluate PCM: Consider checking the PCM for any faults or issues. Test Charging System: Perform a comprehensive test of the charging system, including voltage output and grounding.

How to fix P0622 – learn from mechanics

I looked into P0622 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Dodge

Vehicle Information: 2012 Dodge Grand Caravan SXT 3.6L

Issue + Repair History:

• Cooling fans inoperative.
• Scanned for codes, found P0480 (cooling fan 1 circuit) and P0622 (generator field circuit).
• Fans operational at 220 degrees and with A/C command.
• Checked low-speed relay in TIPM, fans ran when pins 30 & 87 crossed.
• Voltage drop in alternator observed.

Suggestions to Fix Issue:

• Check if Chrysler has a recall for alternator replacement.
• Verify alternator’s sense voltage and PCM regulator.
• Inspect alternator for oil spillage and cleanliness.
• Address the P0622 code, check the field control circuit.
• Ensure good grounds for fan and alternator; they may share a ground.
• Perform voltage drop test for power and ground.
• Consider the possibility of a faulty TIPM.

Final Fix:

• The vehicle was fixed by replacing the TIPM.
• The alternator code P0622 did not reappear after the fix.

Case #2: Chevrolet

Vehicle Information: 2010 Chevrolet Malibu LT 2.4L

Issue + Repair History:

• Intermittent battery warning light.
• Battery replaced but the light persisted.
• Used alternator installed; however, the light continued to come on.
• Load test showed alternator output over 100 amps.
• Diode pattern checked and appeared normal.
• Scanned for codes, found P0622 and B1325.
• Charging voltage consistent across PCM, BCM, and IPC.
• TechIIwin used to command IPC lights on/off, battery light remained off until key cycled.

Other OBD2 Codes + Test Results:

• P0622.
• B1325.

Suggestions to Fix Issue:

• Check if there’s a recall on the alternator.
• Verify alternator’s sense voltage.
• Inspect alternator for oil spillage and cleanliness.
• Check the monitoring line from the regulator to the alternator for duty cycle.
• Ensure all related grounds are good.
• Consider the possibility of a faulty alternator or wiring to the ECM.

Final Fix:

• Found a damaged portion of wire in the grey wire leading back to the PCM.
• The grey wire sends a duty-cycled signal to the PCM to monitor field circuit performance.
• Repairing the damaged wire resolved the issue.

Case #3: Ford

Vehicle Information: 2003 Ford Crown Victoria 4.6L

Issue + Repair History:

• Battery light on, voltage fluctuating between 13.5 volts and 16.2 volts.
• Alternator and battery replaced, but the issue persisted.
• Found melted 3-wire plug to alternator, which was then replaced.
• Scanned for codes, found P0622, but dealerships and all data had no record of it.
• Rebuilt alternator installed, still had issues, and then sent back for proper rebuild.

Other Test Results:

• Voltage unstable.

Suggestions to Fix Issue:

• Ensure the correct alternator is installed, especially one controlled by PCM.
• Check main wiring in front of the right front tire and below the battery.
• Consider replacing the alternator with a Motorcraft remanufactured part.
• Perform voltage drop tests on the charging system.

Final Fix:

• Rebuilt alternator sent back for proper rebuilding.
• After reinstalling, voltage stabilized within range (14.1 volts to 13.8 volts) and battery light did not appear.

Case #4: Chrysler

Vehicle Information: 2000 Chrysler Town & Country Limited 3.8L

Issue + Repair History:

• Battery light on, with voltage fluctuating from 13.5 to 16.2 volts.
• Battery and alternator replaced.
• Found 3-wire plug to alternator melted and replaced it.
• Scanned for codes, found P0622, but information on the code was unclear.

Other OBD2 Codes + Test Results:

• P0622

Suggestions to Fix Issue:

• Check wiring connections, especially at the alternator and PCM.
• Inspect large wiring harness underneath the battery for acid corrosion.
• Ensure the correct alternator is used, specific to PCM controlled charging.
• Perform voltage drop tests on the charging system.
• Check for broken wires inside connectors, especially at the alternator and PCM.

Final Fix:

• Found that the alternator installed was from a different model year.
• Sent the original alternator for rebuilding, considering it was PCM controlled.
• After alternator rebuild and installation, the charging system stabilized and the code did not reappear.

Case #5: Pontiac

Vehicle Information: 2001 Pontiac Sunfire SE 2.4L

Issue + Repair History:

• SES light on with codes P0622 and P0621 (Generator “F” and “L” control circuit problem).
• Battery light intermittently on; battery replaced by customer.
• Alternator replaced, but SES light and codes remained.
• Continuity between generator and PCM connectors found to be fine.
• Alternator output at 14.3 volts.

Other OBD2 Codes + Test Results:

• P0622
• P0621

Suggestions to Fix Issue:

• Ensure the correct alternator, specifically from AC Delco, is used.
• Check voltage at “L” and “F” wires from PCM to generator.
• Inspect harness and connector near exhaust crossover pipe.
• Confirm 5 volts from PCM to generator on “L” wire.
• Check for possible short in the alternator’s exciter wire (“F” term).

Final Fix:

• Replacing the alternator with an AC Delco unit resolved the issue.

Advice	Brief Description of Diagnostic Step
Ensure Correct Alternator	Verify that the alternator is the correct model, particularly for PCM-controlled systems.
Check Alternator Output	Test the alternator’s output to ensure it is within the proper voltage range.
Inspect Wiring and Connections	Examine wiring, especially at the alternator, for damage, corrosion, or poor connections.
Test Generator Field Wire	Check the generator field wire for continuity and proper signal from the alternator to the PCM.
Replace Faulty Alternator	If the alternator is found to be faulty, replace it with a quality or OEM part.
Check for Proper Grounding	Ensure that the alternator and related components are properly grounded.
Clear Codes After Repair	After repairs, clear any diagnostic trouble codes and retest the system.
Inspect for Corrosion or Damage	Look for signs of corrosion or damage in the electrical system, particularly near the battery.