Skip the auto shop - Our mechanics make house calls

P0620 OBD-II Trouble Code: Generator Control Circuit Malfunction

check engine light

P0620 code definition

Code P0620 is stored when the ECM detects a voltage other than what was anticipated.

What the P0620 code means

The PCM controls your vehicle’s generator through a generator turn-on signal circuit, allowing it to turn the generator off and on. When the generator needs to come on, the PCM sends a five-volt signal through the generator turn-on signal circuit to the voltage regulator. Doing so allows the voltage regulator to start controlling the generator field circuit.

As soon as the generator is enabled, the voltage regulator can control the generator output independent of the PCM. Under some operating conditions, the PCM can turn off the five-volt signal and, thus, turn off the generator too.

The PCM also has fault-detection circuitry to monitor these operations. If it detects an unexpected voltage or any other problem, it can cut or reduce the power. This is also when the P0620 code gets stored.

What causes the P0620 code?

There are a number of reasons your vehicle’s PCM may record a P0620 code. These would be:

  • The voltage regulator has malfunctioned
  • The generator is faulty
  • A battery charge
  • The generator circuit is suffering from a poor electrical connection
  • The generator harness is open or shorted
  • The PCM is faulty (this one is the least likely cause)

What are the symptoms of the P0620 code?

When the P0620 code is stored, you should see your Check Engine Light come on. Unfortunately, that’s about the only noticeable symptom associated with this code.

How does a mechanic diagnose the P0620 code?

Your mechanic will use an OBD-II scanner to check which trouble codes your vehicle has stored. They’ll then check the generator for any signs of a bad connection or damage that may have caused a misread of the voltage. The various circuits associated with the generator will have to be looked at too. All the wires involved with this component will also need to be examined, as well as the connectors.

If everything else checks out, the mechanic will check the PCM to make sure it didn’t store the code erroneously.

Common mistakes when diagnosing the P0620 code

This problem can be a difficult one to properly diagnose, which is why it’s important your mechanic doesn’t immediately just assume the PCM was in error. To make sure it’s not the fault of the PCM, the system should be cleared and a test drive conducted to see if the code returns.

Otherwise, the mechanic could replace your PCM needlessly – and charge you in the process – when something like the wiring was actually responsible.

How serious is the P0620 code?

Although it may seem like a minor problem because there aren’t any noticeable symptoms, the P0620 code is still something you’ll want to get repaired ASAP. The transfer of electricity and your vehicle’s generator are both important to its overall functioning and code P0620 could be the beginning of a much bigger problem if you don’t address it right away.

What repairs can fix the P0620 code?

Your mechanic will probably have to do one of the following:

Again, this last option is almost never necessary.

Additional comments for consideration regarding the P0620 code

The same problem that caused the P0620 code to be stored could also be behind others. Just because there isn’t a problem code stored for those yet doesn’t mean your mechanic shouldn’t take the time to do a thorough inspection and ensure other parts of your vehicle aren’t suffering because of abnormal voltages.

Need help with a P0620 code?

YourMechanic is here to make it as convenient as possible to have your vehicle diagnosed and repaired. Just complete this online form for a quick quote and to schedule your appointment. You can even give us a call at 1-800-701-6230 to speak with a friendly service advisor. Once your appointment comes, a certified mobile mechanic will come to your home or office to handle repairs on the spot.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...


Related questions

Q: Will a bad O2 sensor damage my car's computer?

The engine control unit (ECU) is a possible cause of the O2 sensor fault codes but not the most likely. Your vehicle is equipped with 4 O2 sensors. Bank 1 is the driver's side. Bank 2 is the passenger side....

Q: When engine is cold it studders and misses but when warm it runs juss fine no codes and engine light isnt on why is this happening

When an engine is cold it will need more fuel to run correctly. I would recommend having the fuel injection system cleaned to see if it helps to run better. If the flush does not work then a scan will...

Q: Check Engine Light code P2544

The short answer is yes, the tire size can cause the P2544 code. This code sets when the computer sees that the vehicle speed and the requested torque tables in the transmission control module don't coincide. So, a different tire...