This is a stretch but does anybody have access to cable diagrams? I just swapped in an engine and am getting “Charging System Service Now” light. Battery is good. New alternator. New battery/starter harness. During idle, voltage across battery is 14V. No loose grounds. After some process of elimination , I believe it is due to the having the wrong harness for my car.



I know there are unique starter harnesses for each engine, trim and transmission. I just realized that I put in the wrong one, WC96636 (GR3Z-14300-AN). The correct one for my car is WC96709 (GR3Z-14300-BA)



Before I go through the effort of taking out the harness, I would like to see the difference between the two cable assemblies. Maybe they have different BMS sensor and I can just take the sensor off my old harness and swap it in.

Do you have the original alternator? If so swap it in. I will buy the Boss alternator from you if that is the issue, I do not think it is though. Did you swap an AGM battery in to test? If the car is running well with no other codes/warnings I think the Anti Gravity battery is the issue. Same symptoms I had using that battery. If an AGM was tried and still have the warning then alternator may be incompatible with Gen 2. (Again I doubt this).

Also try and unplug the connector on the alternator. Leave just the main charge cable connected. See if error goes away. The lithium battery doesn't act as a capacitor as well as conventional and AGM batteries do. A lot of Mustang racers run without his connector plugged in. I do not and had no issue with Braille or now returned to OEM AGM, with Boss alternator.

Thank you Steve as always for the insight. I will see about a new battery. I put the car in ET mode and found a code related to battery but it shows has historic instead of current. Interesting find

Code is F00316

What F00316 Means (IPC Engineering Mode)

• • Instrument Cluster Specific: According to driver discussions on platforms like Reddit, F00316 appears inside the hidden engineering/diagnostic menu of the instrument cluster. [1]
  • Historical or Non-Critical: Many codes in this menu are stored for internal record-keeping or tracking minor electrical/cluster anomalies rather than signaling a mechanical failure. [1]
  • Battery Check: Some users note that minor cluster or voltage-related quirks can trigger unusual codes, making it a good idea to test your 12V battery health if you are experiencing electrical glitches. -Note the Battery check comment. The battery isn't bad, it just doesn't act the way Ford engineering expects it to.

From the Googles (have not verified myself) --

Manual BMS Reset Procedure
1. Turn on ignition: Switch the ignition to the ON position (do not start the engine; press the start button twice without pressing the brake pedal, or turn the key to ON).
2. Flash high beams: Within 10 seconds of turning the ignition on, pull and release the high-beam headlamps 5 times (ending with the high beams off).
3. Press the brake pedal: Press and release the brake pedal 3 times.
4. Confirm reset: Watch the instrument cluster; the battery warning light will flash 3 times to confirm the BMS reset is complete.
Alternatively, you can let the vehicle sit undisturbed for approximately 8 hours with the doors closed and no key fob button presses so the system can automatically relearn the battery state of charge.