Saab 9-5 P0622:  Meaning, Causes + Diagnosis

by

P0622 Saab 9-5

P0622 is a somewhat rare OBD2 trouble code.  It’s a general code, meaning it has the same definition for the Saab 9-5 as it would any other vehicle.  This code indicates the generator field coil control circuit is malfunctioning.  It can be a challenge to diagnose.

P0622 Meaning:  Generator Field F Control Circuit Malfunction

“Generator field coil” is not a term that is thrown around a whole lot.  It’s an inner part of the alternator.  Here’s a quick explanation of the definition of P0622 for the Saab 9-5:

Generator Field F Control Circuit

P0622 Meaning Saab 9-5

The generator field coil is a stationary part of the alternator.  If you’ve ever held a new alternator, you can see the copper windings inside of it.  It isn’t so easy to see once it’s dirty.  You can see a generator field coil is easily seen in the pic directly above.  

The generator field control circuit controls the generator field coil.  The 9-5’s PCM will send the generator turn-on signal to the alternator.  After that, the voltage regulator will begin controlling the output of the alternator by itself.  

You can not replace the generator field coil by itself.  The whole alternator would need replacing. 

Malfunctioning

When the PCM commands the alternator to turn on, it can detect an issue with the generator field control circuit.  If it does, it’ll throw P0622.

9-5 P0622 Symptoms

9-5 P0622 Symptoms

Symptoms of P0622 include:

Most of the symptoms of P0622 are related to the low voltage coming from the alternator.

Saab 9-5 P0622 Causes + Diagnosis

P0622 Diagnosis

Here are the likely causes of P0622 in the Saab 9-5, as well as a good order to proceed with your diagnosis.

P0622 is difficult to diagnose at home, as specialty diagnostic equipment that most folks don’t have is required for some parts.

1. Check for other Codes

Other codes related to the charging system can help you narrow down why P0622 appeared in your 9-5’s PCM memory.

Make sure you record any codes that were listed and then clear the memory.  You should also record the freeze frame data if you know how to read it.  It’ll prove valuable if the code ends up appearing intermittently.

Now that you’ve captured this data, it’s time to clear the codes.  Drive your 9-5 and see if you can get the code to come back.  Sometimes the code is VERY INTERMITTENT.  In this case, without the freeze frame data, you’ll have to wait for it to come back.

2. Check the Battery/Chassis/Engine Ground Wire

While it’s not the most likely cause of P0622, bad ground wires to the chassis are known to cause issues with the generator field control circuit.  

If you find a loose or corroded ground wire, clean it, make sure it’s bolted tightly, and clear the code.

3. Check the Generator Field Control Circuit

This is going to involve getting the wiring schematic for your 9-5’s exact model year and engine combination.  Once you have them, you can begin testing the wiring harness.

  1. Make sure that the battery is sufficiently charged.
  2. Confirm that there is battery voltage on the generator field control circuit.  (If there is, then it’s likely that the alternator will need to be replaced).  If there’s no voltage, you’re going to need to find out why.
  3. If the alternator is putting out the proper voltage, check the fuses and relays in the field control circuit to ensure they are getting power.
  4. Inspect the wiring harness for signs of damage.  Being in the engine compartment can be difficult for a wiring harness.
  5. If all of the wiring looks good, it’s time to consider a new controller.  You’ll most likely need to have it programmed for your vehicle if you’re buying it used.  

4. Bad Alternator

A bad alternator can cause P0622 in the Saab 9-5, but it shouldn’t be where you start your diagnosis.  People often replace both the alternator and the battery when this code comes up and will still end up with the battery light on and P0622.

While the generator field coil is inside the alternator, the controller is not, and P0622 deals with the controller.  It’s no guarantee that replacing the alternator will solve the issue causing the code.

Conclusion

P0622 can be a tough code to diagnose at home.  While there are some things you can do, you may have to have your Saab 9-5 looked at by a professional.