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P0622 Code 06 GT 4.6L

407 Views 13 Replies 5 Participants Last post by  GTPONY08
Replaced stock alternator about a month ago. Carquest brand New not Rebuilt. My brother in law's mechanic shop uses Advanced Auto for all their parts so I get a deal on parts going through his account. I replaced it myself, no big deal. My Charging System and battery light will come on while driving, for a minute or so, then goes away. This happened several times on my 22 mile drive to work this morning. Came on once 2 days ago then didn't happen again until this morning.
I have a Bama Tuner, code was P0622 Generator Field/F Terminal Circuit.
Tested as follows, Charging System NOT displayed at time of test.
Car not running - 12.43 Amps. LED Headlights on 12.18. LED Headlights and LED fog lights 12.12 on.
Car running - Bounces between 14.06 lowest, 14.43 highest. Headlights on 14.06 lowest, 14.18 highest reading. Headlights and fogs, 14.00 lowest, 14.50 highest.
Motor revved 14.50 highest reading.

I have some research to do when I get home.
Question. Only motor mod is Bama 93 Octane tune for the JLT CAI. Would a high output alternator be needed? My guess is no. The OEM Motorcraft alternator is almost $100 more. Should I go with OEM?

I will check my connections and maybe replace alternator to battery cable.
Any thoughts? Thanks in advance.
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Could be the signs of a plate inside the battery felling. My Explorer did the same thing. Light would come and go random. Then all of a sudden one day out of nowhere the battery was dead to the world.
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It sounds like your alternator is working just fine. However I wouldn't rule out the possibility that a diode is intermittently failing.
Check the connections as you suggested and see if you need to add an extra ground cable from the alternator casing to the passenger strut tower.
Replaced stock alternator about a month ago. Carquest brand New not Rebuilt. My brother in law's mechanic shop uses Advanced Auto for all their parts so I get a deal on parts going through his account. I replaced it myself, no big deal. My Charging System and battery light will come on while driving, for a minute or so, then goes away. This happened several times on my 22 mile drive to work this morning. Came on once 2 days ago then didn't happen again until this morning.
I have a Bama Tuner, code was P0622 Generator Field/F Terminal Circuit.
Tested as follows, Charging System NOT displayed at time of test.
Car not running - 12.43 Amps. LED Headlights on 12.18. LED Headlights and LED fog lights 12.12 on.
Car running - Bounces between 14.06 lowest, 14.43 highest. Headlights on 14.06 lowest, 14.18 highest reading. Headlights and fogs, 14.00 lowest, 14.50 highest.
Motor revved 14.50 highest reading.

I have some research to do when I get home.
Question. Only motor mod is Bama 93 Octane tune for the JLT CAI. Would a high output alternator be needed? My guess is no. The OEM Motorcraft alternator is almost $100 more. Should I go with OEM?

I will check my connections and maybe replace alternator to battery cable.
Any thoughts? Thanks in advance.
Normally I would agree that a bad battery is the likely issue seeing how the alternator is pumping out a reasonable amount of volts but there's the P0622 code. This trouble code means that the PCM has detected an unexpected voltage condition in the alternator control circuit. The alternator can be defective with an open or short in it or somewhere in the control circuit from the alternator to the PCM. There's likely a short in the alternator or wiring that may be decharging the battery when the car is off. It's usually either that, a wiring issue, or the PCM itself with this particular trouble code.
Seeing how you just replaced the alternator recently this would be a prime suspect and the alternator is usually the cause of this code. The wiring/connectors from the alternator to the PCM is probably the second most likely cause.
Since you have less than 12.5v when the car is sitting just to rule the battery out I would disconnect the battery from the cables and then charge the battery with a charger. After it's got at least 12.7 or so volts in it then leave it disconnected for a few hours and see if it decharges much. If it does then you know that the battery is bad but if it stays at a stable voltage above 12.5v then your battery is likely fine. I would also load test the battery as well. If the battery is more than 5 years old it might be a good idea to replace it with a Motorcraft battery.
Just because you bought a supposedly brand new auto parts store alternator really doesn't mean much since even most new alternators are also made with inferior parts. Only a true high quality manufacturer will use high quality parts and conduct proper testing. PA Performance is going to be your only really good option for a new alternator since Ford doesn't sell new alternators only 3rd party rebuilt ones packaged in their box.
Replaced stock alternator about a month ago. Carquest brand New not Rebuilt. My brother in law's mechanic shop uses Advanced Auto for all their parts so I get a deal on parts going through his account. I replaced it myself, no big deal. My Charging System and battery light will come on while driving, for a minute or so, then goes away. This happened several times on my 22 mile drive to work this morning. Came on once 2 days ago then didn't happen again until this morning.
I have a Bama Tuner, code was P0622 Generator Field/F Terminal Circuit.
Tested as follows, Charging System NOT displayed at time of test.
Car not running - 12.43 Amps. LED Headlights on 12.18. LED Headlights and LED fog lights 12.12 on.
Car running - Bounces between 14.06 lowest, 14.43 highest. Headlights on 14.06 lowest, 14.18 highest reading. Headlights and fogs, 14.00 lowest, 14.50 highest.
Motor revved 14.50 highest reading.

I have some research to do when I get home.
Question. Only motor mod is Bama 93 Octane tune for the JLT CAI. Would a high output alternator be needed? My guess is no. The OEM Motorcraft alternator is almost $100 more. Should I go with OEM?

I will check my connections and maybe replace alternator to battery cable.
Any thoughts? Thanks in advance.
Thanks. I plan on changing the alt cables tomorrow. Charge up battery, which I failed to mention is a 4 month old Interstate battery, but can't rule out the obvious first.
It sounds like your alternator is working just fine. However I wouldn't rule out the possibility that a diode is intermittently failing.
Check the connections as you suggested and see if you need to add an extra ground cable from the alternator casing to the passenger strut tower.
Thank you for the in depth reply. I did neglect to check the PCM wiring. As with this year Mustang I had problems when heavy rain caused flooding inside and into the passenger side kick panel. I cleared out the clogged drain holes but it's been 8 months or so. Put dielectric grease on the connector once it dried out. It got wet and my parking lights were doing some weird stuff. Either factory or original owner taped a piece of thin layer coated Styrofoam over the computer. Is this the location of PCM you're referring to or the one under the hood? The battery is about 8 month old Interstae battery but it's second battery I've replaced in the past 3 years. Seems I get about 3 years (had the car now for 7 years) out of the battery, right close to the end of warranty. Interstate is one of the better batteries out there and thought it would last longer than 3 years. Maybe I have an underlying problem as you suggested, draining the battery over time. I will update my progress.
Normally I would agree that a bad battery is the likely issue seeing how the alternator is pumping out a reasonable amount of volts but there's the P0622 code. This trouble code means that the PCM has detected an unexpected voltage condition in the alternator control circuit. The alternator can be defective with an open or short in it or somewhere in the control circuit from the alternator to the PCM. There's likely a short in the alternator or wiring that may be decharging the battery when the car is off. It's usually either that, a wiring issue, or the PCM itself with this particular trouble code.
Seeing how you just replaced the alternator recently this would be a prime suspect and the alternator is usually the cause of this code. The wiring/connectors from the alternator to the PCM is probably the second most likely cause.
Since you have less than 12.5v when the car is sitting just to rule the battery out I would disconnect the battery from the cables and then charge the battery with a charger. After it's got at least 12.7 or so volts in it then leave it disconnected for a few hours and see if it decharges much. If it does then you know that the battery is bad but if it stays at a stable voltage above 12.5v then your battery is likely fine. I would also load test the battery as well. If the battery is more than 5 years old it might be a good idea to replace it with a Motorcraft battery.
Just because you bought a supposedly brand new auto parts store alternator really doesn't mean much since even most new alternators are also made with inferior parts. Only a true high quality manufacturer will use high quality parts and conduct proper testing. PA Performance is going to be your only really good option for a new alternator since Ford doesn't sell new alternators only 3rd party rebuilt ones packaged in their box.
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After proof reading. It is the second battery in 6 years, not 3 years. Replaced about every 3 years since I've owned the car.
Thank you for the in depth reply. I did neglect to check the PCM wiring. As with this year Mustang I had problems when heavy rain caused flooding inside and into the passenger side kick panel. I cleared out the clogged drain holes but it's been 8 months or so. Put dielectric grease on the connector once it dried out. It got wet and my parking lights were doing some weird stuff. Either factory or original owner taped a piece of thin layer coated Styrofoam over the computer. Is this the location of PCM you're referring to or the one under the hood? The battery is about 8 month old Interstae battery but it's second battery I've replaced in the past 3 years. Seems I get about 3 years (had the car now for 7 years) out of the battery, right close to the end of warranty. Interstate is one of the better batteries out there and thought it would last longer than 3 years. Maybe I have an underlying problem as you suggested, draining the battery over time. I will update my progress.
Interstate is an excellent brand and should last well more than 3 years. Test the battery when isolated from the rest of the car to check if it's ok.
It's doubtful that the main cables are the issue here. The voltage anomaly is being detected in the control circuit which means it's almost certainly the alternator itself or any of the wiring/connectors from it to the PCM.
is a 4 month old Interstate battery
Thank you for the in depth reply. I did neglect to check the PCM wiring. As with this year Mustang I had problems when heavy rain caused flooding inside and into the passenger side kick panel. I cleared out the clogged drain holes but it's been 8 months or so. Put dielectric grease on the connector once it dried out. It got wet and my parking lights were doing some weird stuff. Either factory or original owner taped a piece of thin layer coated Styrofoam over the computer. Is this the location of PCM you're referring to or the one under the hood? The battery is about 8 month old Interstae battery but it's second battery I've replaced in the past 3 years. Seems I get about 3 years (had the car now for 7 years) out of the battery, right close to the end of warranty. Interstate is one of the better batteries out there and thought it would last longer than 3 years. Maybe I have an underlying problem as you suggested, draining the battery over time. I will update my progress.
The SJB is located in the passenger compartment. That's just a glorified BCM though it does route PATS and other communication from the PCM to the cluster. It's such a common source of trouble because it puts too many eggs in one basket(terrible design imo) and along with the unforgivable water leak issues it's the source of many electrical problems. This isn't the likely issue here though. I've seen a cover on the SJB on the 2005+ Mustangs that might have been put there at the factory, dealer, or an owner, idk.
The PCM is located in the engine compartment. It's on the passenger side and is bolted to the side of the underhood fuse box. Any of the wiring and connectors coming off the alternator should be checked. The PCM connector where those wires go into should also be inspected.
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Thanks for the clarification. I pulled the battery today and set on a trickle charge. I'll inspect all the wiring to PCM. I had to give this information off of the PCM for my Bama tuner.
Interstate is an excellent brand and should last well more than 3 years. Test the battery when isolated from the rest of the car to check if it's ok.
It's doubtful that the main cables are the issue here. The voltage anomaly is being detected in the control circuit which means it's almost certainly the alternator itself or any of the wiring/connectors from it to the PCM.

The SJB is located in the passenger compartment. That's just a glorified BCM though it does route PATS and other communication from the PCM to the cluster. It's such a common source of trouble because it puts too many eggs in one basket(terrible design imo) and along with the unforgivable water leak issues it's the source of many electrical problems. This isn't the likely issue here though. I've seen a cover on the SJB on the 2005+ Mustangs that might have been put there at the factory, dealer, or an owner, idk.
The PCM is located in the engine compartment. It's on the passenger side and is bolted to the side of the underhood fuse box. Any of the wiring and connectors coming off the alternator should be checked. The PCM connector where those wires go into should also be inspected.
When my battery died both times no warning. The dummy gauge needle never moved, battery light didn't come on. Both times went to start to go work and it was dead. Now since I have the tuner I keep an eye it.
Could be the signs of a plate inside the battery felling. My Explorer did the same thing. Light would come and go random. Then all of a sudden one day out of nowhere the battery was dead to the world.
Been through this with my 07. Had to use a stock alternator from Ford.
Replaced stock alternator about a month ago. Carquest brand New not Rebuilt. My brother in law's mechanic shop uses Advanced Auto for all their parts so I get a deal on parts going through his account. I replaced it myself, no big deal. My Charging System and battery light will come on while driving, for a minute or so, then goes away. This happened several times on my 22 mile drive to work this morning. Came on once 2 days ago then didn't happen again until this morning.
I have a Bama Tuner, code was P0622 Generator Field/F Terminal Circuit.
Tested as follows, Charging System NOT displayed at time of test.
Car not running - 12.43 Amps. LED Headlights on 12.18. LED Headlights and LED fog lights 12.12 on.
Car running - Bounces between 14.06 lowest, 14.43 highest. Headlights on 14.06 lowest, 14.18 highest reading. Headlights and fogs, 14.00 lowest, 14.50 highest.
Motor revved 14.50 highest reading.

I have some research to do when I get home.
Question. Only motor mod is Bama 93 Octane tune for the JLT CAI. Would a high output alternator be needed? My guess is no. The OEM Motorcraft alternator is almost $100 more. Should I go with OEM?

I will check my connections and maybe replace alternator to battery cable.
Any thoughts? Thanks in advance.
Your current issue now hasn't had your battery die, correct? Just the battery light and alternator circuit trouble code?
When my battery died both times no warning. The dummy gauge needle never moved, battery light didn't come on. Both times went to start to go work and it was dead. Now since I have the tuner I keep an eye it.
Been through this with my 07. Had to use a stock alternator from Ford.
Ford doesn't sell new alternators when they're available, only 3rd party rebuilt ones packaged in their box. They should be better quality than a typical rebuilt or budget new one but it really all depends on the rebuilder that does it for them. I would think that Ford would insist that a rebuilder only use high quality parts.
I looked into the PA Performance alternator on their website. 2005-2008 Mustang (2158W)
2005-2008 Mustang (2158W) Going by description it's a 160 max amp.
$319.00.

I'm going to change out the Carquest alternator and get a refund.

What is your take ordering through American Muscle? PA Performance Alternator; 130 Amp
(05-08 Mustang GT)
Our Price $287.10

I have the Power alternator wire kit due in Thursday. PA Performance Mustang Premium Power Wire Kit 9909 (94-14 Mustang, Excluding GT500) - Free Shipping
Normally I would agree that a bad battery is the likely issue seeing how the alternator is pumping out a reasonable amount of volts but there's the P0622 code. This trouble code means that the PCM has detected an unexpected voltage condition in the alternator control circuit. The alternator can be defective with an open or short in it or somewhere in the control circuit from the alternator to the PCM. There's likely a short in the alternator or wiring that may be decharging the battery when the car is off. It's usually either that, a wiring issue, or the PCM itself with this particular trouble code.
Seeing how you just replaced the alternator recently this would be a prime suspect and the alternator is usually the cause of this code. The wiring/connectors from the alternator to the PCM is probably the second most likely cause.
Since you have less than 12.5v when the car is sitting just to rule the battery out I would disconnect the battery from the cables and then charge the battery with a charger. After it's got at least 12.7 or so volts in it then leave it disconnected for a few hours and see if it decharges much. If it does then you know that the battery is bad but if it stays at a stable voltage above 12.5v then your battery is likely fine. I would also load test the battery as well. If the battery is more than 5 years old it might be a good idea to replace it with a Motorcraft battery.
Just because you bought a supposedly brand new auto parts store alternator really doesn't mean much since even most new alternators are also made with inferior parts. Only a true high quality manufacturer will use high quality parts and conduct proper testing. PA Performance is going to be your only really good option for a new alternator since Ford doesn't sell new alternators only 3rd party rebuilt ones packaged in their box.
Correct. Since the Interstate Battery was under warranty they gave me a new battery.
I rode to work this morning with my SCT tuner hooked up for the ride on gauge data log. I forgot to record but watching as I drove the charge system and battery light went on and off 3 separate times in the 22 mile trip. I stated off driving the first few miles at 14.06 Amps. When the warning was lit I did not see any difference in the amp output. The 3rd time the warning went away the amp reading was in the 12 amp range. I exited the freeway (all freeway miles non stop). When light turned green I romped on it a little and Amps went back to 14.
Your current issue now hasn't had your battery die, correct? Just the battery light and alternator circuit trouble code?

Ford doesn't sell new alternators when they're available, only 3rd party rebuilt ones packaged in their box. They should be better quality than a typical rebuilt or budget new one but it really all depends on the rebuilder that does it for them. I would think that Ford would insist that a rebuilder only use high quality parts.
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