Well I've got 2 things going on. For the past week I've had a small draw on the batteries, if I let them sit for more then 2 days they'll be dead. Then, this morning the alternator starts charging out of control and I get code 1594. I always thought the pcm regulated voltage, but could it still be a problem in the alternator? (alternator is 6 months old from NAPA).

 

Pulled the rest of the codes. 1594, 622,743 and 1765. The last three have been there since I put a TC lockup switch in last year.

 

P0622 Generator Field "F" Control Circuit Malfunction

P0743 Torque Converter Clutch Circuit Electrical

P1594 Charging System Voltage Too High

P1765 Trans 12 Volt Supply Relay Control Circuit


There are 2 common draws you should look for that could kill your batteries. One of the grid heater solenoids could be stuck on.....and the fuel heater relay could be stuck on.....I have seen both problems before. That said, the grid heater solenoid will probably kill the batteries faster than 2 days.

The one DTC that concerns me is the 0622....I have heard of malfunctioning diodes in the fields allow electricity to flow backwards into the field magnets when the alternator is not turning which in turn allows for discharging of the battery when the engine is not running......this makes me wonder about the "Field F circuit malfunction".

As far as charging voltage being too high, it is completely regulated by the PCM....there is nothing to do with voltage regulation within the alternator.

Hopefully, someone else can chime in about the 0622 DTC.

 

If I put the trans relay back in and clear the codes, 743, 622, and 1765 are gone. Bad pcm seem likely but I was hopping it was something else, or at least something cheaper (dealer wants $710 for a pcm )

 

update:
Trucks been driving fine for the past week, until tonight. It starts charging @ 18 volts again, so I pull the connector at the alternator so I can drive home. But after about a mile the volt meter drops to 8 volt and now I have no low beams!

 

Well, my PCM has been out since august and is sitting under my seat with one of the electrolytic capacitors on the power circuit literally fried off the board. I've been running a contact point/electro magnet style voltage regulator lately... I can get a few pics to show you what wires need to be tapped into and make some notes for you. I've also been running my TCC and OD with toggles since then too. Should you start to have issues with OD I can help you with putting a switch in.

 

Alright, low beams burnt out because of the high voltage. But I couldn't figure out why after a mile the gauge only showed 8 volts. Then I got to thinking, the PCM watches 2 things when deciding how to charge, battery temp and battery voltage. If it was only seeing 8 volts then it probably went to full field charge to try to bring voltage back up. What do ya think, should I be looking for a bad connector in the power circuit.