13 impala starting issues

My car has had issues in the past where it would say “starting disabled, service throttle”. Strangely this would only happen if the fuel level was below 1/4 left. It would also allow me to start the car by unplugging the battery briefly. I replaced the throttle and hadn’t had any issues since. Today it wouldn’t start, no throttle message this time, but fuel was about 25% “coincidence?”. Did the battery trick and it started right up. Filled it up and hasn’t had any issues again. Fuel issue? Electric issue? Starter? The fuel pump was tested and was fine. No blown fuses, replaced throttle. I am upside down on this car with only an emissions warranty left and am running out of ideas, and the mechanic is not a help. Has anyone else had/heard of a similar problem?

I think you simply need a better mechanic.

Does the starter motor turn over the engine as usual, but the engine fails to start and run?

Or does the starter motor not turn over the engine at all?

I’ve taken it to two different gm dealership locations

It does not try to turn over until I disconnect and reconnect the battery when it happens.

Get an OBD II code reader. It should cost less than $30 for a standalone unit–less than $15 for a unit that works in conjunction with your cellphone or tablet. Teach yourself the basics of how to read codes.

At the instant of failure, read the codes and report them to your mechanic. There will be one or more codes, each of “P” followed by four digits. The action of disconnecting the battery resets the codes so your mechanic has been unable to read them.

Auto Zone will lend a code reader for free. Have you considered a RATO?