Hello all and Vstar!
Glad I'm not reviving an old post but merely adding to the long list of cars with this affliction!!
2007 G35x195k.
2 year old Interstate MTX battery, tests 90% on my batt tester.
Original Mitubishi alternator!
3 days ago, wife goes to leave for work, car starts normal, idles normal, she puts in reverse and rolls down the driveway to the street, she accelerates out of the driveway and the car starts surging, she states all the dash lights came on and she turns round and barely made it back up the driveway, she jumps in our sons 2008 ex35x and takes off for work.
I go out to the car, starts normal, idles normal, battery and brake light or on. I drive it to in front of my garage, no surging and no christmas tree on dash, seems normal except battery and brake lights on.
Grab my Autel 808bts and start scanning. What i was after was live data and Actions to see Alternator Duty cycle, which at the time was at 0%. I think that's odd as normally they don't just cut out. So into the house and jump into the FSM to get some diagrams and logic of when the battery light comes on. Back to the car to follow the flow chart for terminal S and L and if both are good then time for an alternator. Which I figured anyway due to the age of the stock one (WELL DONE MITSUBISHI!!) Both terminals good so off to Oreilly to get an Ultima Alt. I've had good luck in the past with these.
Get the old one out and new one in and get it back together and all is good and my scanner says alternator duty cycle is at 40% with high beams, defroster and blower on high, while maintaining 13.6 volts. On to the test drive and a fresh ice coffee and go get my core charge back...except 1 mile from my house the brake and battery light come back on! Back to my house in front of the garage and figure WTF and what did I miss!!
Checked and cleaned all obvious grounds in engine room, installed new battery terminal with a new lug connector on negative cable at battery. Checked voltage drop from batt cable to alternator and still brake and battery light persist. SO I obviously found this post and located pin 76 Violet in IPDM and boom, I got 14.2-14.7 at idle and with accessory loads with the alternator duty at 30.5%, I'm a happy guy and was going to write a thank you post...Until I went for the test drive/fresh ice coffee/core charge return trip and it happens again, same thing as before. Brake and Battery light, 0% Duty cycle and voltage seemingly stays around 11.92ish volts and the lights seem to be flickering when I run the rpms up, so I disco the current sensor thinking that the ecm still has control and no change...SOOOOO, I'm tempted to put a new battery in it to see if I have the red herring as mentioned...????
If you read all of this I owe you a frosty one
If you have a any suggestions I owes ya two frosty ones! THANKS!