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Rock Sam

Rock Sam 8/7/2018

2008 Hummer H3 Base 5 Cyl 3.70L


How do I diagnose P0622 OBD-II Trouble Code OBD-II Trouble Code of my car and what are its causes?

1 Answer

PartsAvatar Ca

PartsAvatar Ca 8/7/2018

What the P0622 code means?

When the PCM (powertrain control module) logs a P0622 trouble code, it's because it's detected a problem with the generator field control circuit. The PCM uses the generator turn-on signal circuit to manage the generator. When it wants to take control, it sends a five-volt signal to the voltage regulator through the generator turn-on signal circuit. This forces the voltage regulator to start controlling the generator field circuit. Once the PCM enables the generator, the voltage regulator independently controls the generator. However, during this process, if it notices something is wrong with the generator field circuit, this trouble code is stored.

What causes the P0622 code?

• Faulty PCM PCM.

• programming error.

• Open or shorted generator field control circuit.

• Defective alternator.

What are the symptoms of the P0622 code?

• Engine may not start.

• Engine may stall.

• Symptoms may include a discharged battery, drivability issues, harsh shifting, decreased fuel economy,
the engine may stall or run roughly at idle, poor acceleration, a stored trouble code, and possibly an illuminated service engine soon lamp. If this code is stored, and a service engine soon lamp has not yet been illuminated, the code may be shown as pending.

Common mistakes when diagnosing the P0622 code:

Symptoms and stored codes that are present as a reaction to a communication failure are often misdiagnosed and repaired as the cause of the problem. Obviously, this leads to an unsuccessful repair. Engine misfire codes, lean exhaust codes, fuel injector codes, and virtually any other drivability or transmission code that is accompanied by a controller communication code can potentially be a pitfall for misdiagnosis. Follow the rule that says to diagnose codes in the order in which they are stored and you will improve your chances for a successful diagnosis. Utilize freeze frame data to help you determine which codes were stored first.

What repairs can fix the P0622 code?

There are a few things a mechanic can do to clear this code:

• Disconnect all of the CAN's pins and test each individually.

• Replace the control module ground strap.


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