My 2016 TLX has been acting strange recently. Occasionally, when I park and turn off the engine, the system flashes the "Shift to Park" icon as if I am not in park when I turn off the engine. The engine is cut off but the car goes into Accessory Mode. However, I can't turn off the accessory mode nor restart the engine as the immobilizer icon starts to flash and the engine just clicks and the car goes back to accessory mode. The only solution I have found is to exit the vehicle, insert the key in the door handle and lock the car at which point it completely shuts off. I took it to the dealer and they tested the control unit and the keys (and replaced the batteries in the key fob). The car battery is also new. The dealer tech however could not isolate the problem as the car never exhibited this while with the dealer. So I am out $150 for the diagnostic, with a recurring problem. I was wondering if anyone had encountered something similar.

 

Update: The problem recurred this morning. But this time, I was able to press "start/stop" and while the engine was clicking, managed to shift out of park and back in. Now the car registered that it was in Park mode and allowed me to switch off the engine. So perhaps it is a transmission sensor issue after all?

 

Just guessing here, but it sounds like it could be an issue with the transmission range switch. This tells the car's computer what position the transmission is in. I had to replace one in my MDX about 8 years ago.

 

I think so too. But the dealer insisted that it was something to do with the keyless entry controller. I need to make sure they check the transmission range (or neutral safety switch). This is an intermittent problem and I figured out that if I shift to neutral, I can switch off the engine and shift to park,

 

Wild guess here but check for a failing brake pedal position switch. It allows the gear selector to change gears and start the car. It is #2 in this diagram: Pedal - 2018 Acura TLX 4 Door 24TECH (L4) KA DCT (acurapartswarehouse.com)