Technical Description of OBD-II Trouble Code
The circuit for the Generator Field/F Terminal is experiencing high voltage.
What does that mean?
This is a generic diagnostic trouble code (DTC) that is applicable to many OBD-II vehicles (1996-newer), including vehicles from Ford, Kia, Dodge, Hyundai, Jeep, 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 P0626 indicates that the powertrain control module (PCM) has detected a higher than expected voltage signal from the generator field coil circuit. The “F” in the code indicates that the field coil control circuit is at fault.
The field coil can be identified by its visible windings through the vent holes on most alternators. It surrounds the generator armature and remains stationary in the alternator housing. The armature spins inside the energized field coil using battery voltage. Each time the engine is started, the field coil is energized.
The PCM continuously monitors the continuity and voltage level of the generator field circuit while the engine is running. The generator field coil is essential for generator operation and maintaining battery charge levels.
If a problem is detected in monitoring the generator field circuit, a code P0626 will be stored and a malfunction indicator lamp (MIL) may illuminate. Depending on the perceived severity of the malfunction, multiple failure cycles may be required for MIL illumination.
A typical alternator:
What is the severity of this DTC?
A stored code P0626 could result in various drivability concerns, including a no-start condition and/or a dead battery. It should be considered severe.
What are some of the symptoms of the code?
Symptoms of a P0626 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P0626 troubleshooting steps?
To diagnose a code P0626, 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 technical service bulletins (TSB) that match the stored code, vehicle details (year, make, model, and engine), and exhibited symptoms. If you find the relevant TSB, it may provide helpful diagnostic information.
Start by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. It is advisable 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 reset or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more challenging to diagnose. The condition that caused the P0626 code to be stored may even need to worsen before a diagnosis can be made. If the code is reset, continue with the diagnosis.
Use the battery/alternator tester to load-test the battery and ensure that it is adequately charged. If it is not, charge the battery as recommended and test the alternator/generator. Follow the manufacturer’s specifications for minimum and maximum voltage output requirements for the battery and alternator. If the alternator/generator is not charging, proceed to the next step in your 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 vehicle in question.
Check if there is battery voltage on the alternator/generator field control circuit using the appropriate wiring diagram and your 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.
