Technical Description of OBD-II Trouble Code
Malfunction in the Generator Field F Control Circuit
What does that signify?
This is a generic diagnostic trouble code (DTC) that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from various manufacturers such as Dodge, Jeep, Chevy, Ford, Land Rover, Toyota, Ram, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
A stored code P0622 indicates that the powertrain control module (PCM) has detected a malfunction in the generator field coil control circuit. The “F” simply indicates that the field coil control circuit is at fault.
The field coil is easily recognizable by its windings, which can be seen through the vent holes on most alternators. The field coil surrounds the generator armature and remains stationary in the alternator housing.
The PCM continuously monitors the continuity and voltage level of the generator field control circuit whenever the engine is running. The generator field coil is essential for the operation of the generator and for maintaining battery charge levels.
Each time the ignition is turned on and the PCM is powered, multiple self-tests are performed by the controller. In addition to running internal self-tests, the controller area network (CAN) is used to compare signals from each individual module to ensure proper communication between the controllers.
If a problem is detected in monitoring the generator field control circuit, a code P0622 will be stored and the malfunction indicator lamp (MIL) may illuminate. Depending on the perceived severity of the malfunction, multiple failure cycles may be required for the MIL to illuminate.
A typical alternator:
What is the severity of this DTC?
Internal control module codes should be considered severe. A stored code P0622 could result in various drivability issues, including a no-start condition and/or a dead battery.
What are some of the symptoms of the code?
Symptoms of a P0622 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P0622 troubleshooting steps?
To diagnose a code P0622, you will need a diagnostic scanner, a battery/alternator tester, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
Refer to your vehicle information source for any technical service bulletins (TSB) that match the stored code, vehicle details (year, make, model, and engine), and exhibited symptoms. If you find a relevant TSB, it may provide helpful diagnostic information.
Start by connecting the scanner to the vehicle’s diagnostic port and retrieving all stored codes and freeze frame data. It is important to write down this information in case the code is intermittent. After recording the necessary information, clear the codes and test drive the vehicle until the code is either reset or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and diagnosing the issue will be more challenging. In some cases, the condition that caused the P0622 code to be stored may need to worsen before a diagnosis can be made. If the code is reset, continue with the diagnosis process.
Use the battery/alternator tester to load-test the battery and ensure that it is adequately charged. If the battery is not charged, follow the recommended charging procedure and test the alternator/generator. Refer to the manufacturer’s specifications for the minimum and maximum voltage output requirements for the battery and alternator. If the alternator/generator is not charging, proceed to the next step in the diagnosis.
Use your source of vehicle information to obtain connector face views, connector pin-out charts, component locators, wiring diagrams, and diagnostic flow charts related to the code and the specific vehicle.
Check if there is battery voltage on the alternator/generator field control circuit by referring to the appropriate wiring diagram and using the DVOM. If there is no voltage, check the system fuses and relays and replace any defective parts as necessary. If voltage is present at the generator field coil control terminal, suspect a defective alternator/generator.
If the alternator is charging and the P0622 code continues to reset, use the DVOM to test the power supply fuses and relays for the controller. Replace any blown fuses as needed. Fuses should be tested with the circuit loaded.
If all fuses and relays appear to be functioning correctly, visually inspect the wiring and harnesses related to the controller. Also, check the chassis and engine ground junctions. Use your vehicle information source to find the ground locations for the relevant circuits. Use the DVOM to test the integrity of the grounds.
Inspect the system controllers visually for any signs of water, heat, or collision damage. Any damaged controller, especially if water damage is evident, should be considered defective.
If the power and ground circuits for the controller are intact, suspect a defective controller or a programming error. Replacing the controller will require reprogramming. In some cases, reprogrammed controllers may be available through aftermarket sources. Other vehicles/controllers may require on-board reprogramming, which can only be done by a dealership or another qualified source.
