Error Code P0625 is defined as Generator Field/F Terminal Circuit Low, meaning there’s a problem detected in the generator field control circuit, often caused by too shorted connectors or defective CAN bus.
This is generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. It’s particularly common among vehicle models from Ford, Hyundai, Kia, Land Rover, Mercedes Benz, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from make, model, and powertrain configuration.
When Error Code P0625is stored, that means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has determined a voltage signal that is lower than expected from the generator field coil circuit. The F in the description means the Field Coil Control circuit is at fault.
The Field Coil is arguably the most recognizable from its windings, which are visible through the vent holes of most alternators. It surrounds the generator armature and remains stationary in the housing of the alternator. The armature spins inside the field coil, which the battery energizes. Every time the engine starts, the field coil is energized as well.
Each time the engine runs, the voltage level and continuity of the generator field circuit is monitored by the PCM. The generator field coil plays an important role in the generator’s operation for maintaining battery charge levels.
If the PCM sees a problem while monitoring the generator field circuit, then it will register the fault code and activate the Check Engine light. Depending on the severity of the condition, it may take multiple failure cycles before the Check Engine light lights up.
As said earlier, this code activates the Check Engine light, but it will also activate the Charging System lamp. This code causes engine drivability issues such as inadvertent engine shut-off and delayed engine cranking. Other codes could be present as well.
Some common causes of this code include:
- Burnt fusible link
- Blown fuse
- Open or shorted generator field control circuit
- Defective PCM
- A programming error in PCM
How to Check
As with most error codes, diagnosing this fault requires a diagnostic scanner, battery/alternator tester, DVOM (digital volt/ohmmeter), and a reliable vehicle information source.
Look for the vehicle information from the TSB (technical service bulletin) that is parallel with the code stored, vehicle (year, make, and model), engine, and symptoms. If you find the right TSB, then this will give you the right diagnostic information.
Start the diagnosis by connecting the scanner to the vehicle’s diagnostic port and retrieve all stored codes, as well as their freeze frame data. You may write this information down, in case the problem proves to be intermittent. After recording necessary data, clear the codes and then take the vehicle for a test drive until the code resets, or the PCM enters readiness mode. If the PCM enters Readiness Mode, that means the code is intermittent, and the problem must develop further before you can accurately diagnose and do the necessary repair. If the code resets, then continue with the diagnosis.
Then load-test the battery using the battery/alternator tester, make sure it’s properly charged. If it’s not, then charge the battery as recommended and then test the alternator/generator. Make sure you follow recommendations and specifications set by the manufacturer for the minimum and maximum voltage output requirements for the battery and alternator. If the alternator/generator is not charging, then proceed to the next step.
Use vehicle information source to obtain component locations, connector face views, connector pin-out charts, wiring diagram, and diagnostic flow chart related to your vehicle’s error code.
Then, use the appropriate wiring diagram through your DVOM to check to see if there’s battery voltage on the alternator/generator field control circuit. If not, check the system fuses and relays and replace any defective parts. If voltage is discovered at the generator field coil control terminal, then suspect a defective alternator/generator.
How to Fix
Depending upon the diagnosis, common repairs for this code include:
- Replacement of damaged electrical components (blown fuses)
- Replacement of control module ground strap
- Disconnecting of CAN pins and testing them (this can be an expensive and challenging step, and should be done last)
This code could result in a number of drivability issues, such as no-start and dead battery condition. Thus, it should be addressed as soon as possible.
Also, the field coil is an important component of the alternator, and can’t be replaced separately.