P0620 Generator Control Circuit Malfunction
OBD-II Trouble Code Technical Description
Generator Control Circuit Malfunction
What does that mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Hyundai, Mercedes-Benz, Buick, Ford, GMC, Chevrolet, Jeep, Cadillac, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
A stored code P0620 means that the powertrain control module (PCM) has detected a malfunction with the generator control circuit.
The PCM typically energizes and monitors the generator control circuit whenever the engine is running.
Each time the ignition is turned on and the PCM is energized, multiple controller self-tests are performed. In addition to running internal controller self-tests, the controller area network (CAN) is used to compare signals from each individual module to ensure that the various controllers are interacting properly.
If a problem is detected in monitoring the generator control circuit, a code P0620 will be stored and a malfunction indicator lamp (MIL) may be illuminated. Depending upon the perceived severity of the malfunction, multiple failure cycles may be necessary for MIL illumination.
A typical alternator:
What is the severity of this DTC?
Internal control module codes must always be taken seriously. A stored code P0620 could result in a variety of drivability concerns, including a no-start and/or dead battery condition.
What are some of the symptoms of the code?
Symptoms of a P0620 trouble code may include:
Engine drivability issues Engine stall when idling Delayed engine cranking (especially when cold) Other stored codesWhat are some of the common causes of the code?
Causes for this code may include:
Faulty PCM PCM programming error Open or shorted generator control circuit Failed generator assembly Insufficient control module groundWhat are some P0620 troubleshooting steps?
A diagnostic scanner, a battery/alternator tester, a digital volt/ohmmeter (DVOM), and a source of reliable vehicle information will be required to diagnose a code P0620.
Search you vehicle information source for technical service bulletins (TSB) that parallel the code stored, vehicle (year, make, model, and engine), and symptoms exhibited. If you find the right TSB, it may yield diagnostic information that will aid you in a major way.
Begin by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. You will want to write this information down, just in case the code proves to be an intermittent one. After recording all pertinent 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 difficult to diagnose. The condition, which caused the P0620 to be stored, may even need to worsen before a diagnosis can be made. If the code is reset, continue with your diagnosis.
Use the battery/alternator tester to test the battery and make sure that it is sufficiently charged. If it is not, test the alternator/generator. Follow manufacturers recommended 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 to see if there is battery voltage at the alternator/generator by using the appropriate wiring diagram and your DVOM. If not check system fus
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