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P0620 is a diagnostic trouble code (DTC) for "Generator Control Circuit Malfunction". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
Code P0620 is stored when the ECM detects a voltage other than what was anticipated.
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.
There are a number of reasons your vehicle’s PCM may record a P0620 code. These would be:
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.
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.
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.
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.
Your mechanic will probably have to do one of the following:
Again, this last option is almost never necessary.
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.
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