Mustang automatic transmission hard to shift

I had a similar problem with my Mustang. The symptoms sound eerily familiar. Did you try checking the shift lock solenoid? That can sometimes cause the 'no start' issue when it thinks the car isn't in Park or Neutral. Also, is it hard to move the gear shifter? Just trying to narrow things down before you start tearing into the transmission itself.

Thanks for the quick response! I haven't checked the shift lock solenoid specifically. The gear shifter doesn't feel particularly hard to move, but it does feel a bit 'loose', if that makes sense? Is the solenoid difficult to access, or something I could potentially check myself?

Okay, "loose" isn't great. The solenoid itself isn't too hard to get to, usually located near the shifter assembly under the center console. However, with the check engine light and shifting issues, and especially the stored error code, I'm leaning toward the defective control unit diagnosis you mentioned earlier. Based on your symptoms and the stored error code, I'd advise against DIYing a fix. If it's the control unit, you'll need specialized tools and knowledge. A workshop should be able to pinpoint the problem accurately and get you sorted. It may be an expensive fix, but worth it in the long run. Best of luck!

Thanks so much for the advice! It does sound like it's beyond my capabilities. I appreciate you confirming that it's probably best left to the professionals. I'll take it to a workshop and have them check the control unit. It's likely the source of the problem. I'll post the resolution here when I have it.