EV mode with CEL

From your last sentence, I get the impression you want to install the EV button so that you can manipulate the engine to turn off, when it otherwise wants to run, in order to get better fuel economy.

If I am correct, you can save yourself the trouble as it won't achieve that goal.

The EV button is not designed to do that. When the engine is cold, it is to keep the engine off for short movements - say, in and out of the garage or to move around on your driveway. Another legitimate use is driving in a semi-enclosed parking structure with poor ventilation. In this situation, most of the time you will not need it as long as the engine is at operating temperature.

In stop-and-go traffic, it won't make much, if any, difference when the engine is at operating temperature.

On 30 MPH roads, you will not be able to use the EV button unless you are willing to travel 26 MPH (true speed*) or less. This is the speed threshold where EV mode will be forced off.

The other thing to bear in mind in these two scenarios is you're robbing Peter to pay Paul. All energy stored in the battery is derived from burning gas. Together with the energy conversion losses you will always be behind the 8-ball and your fuel economy will be worse as you will need to replace the energy taken from the battery by burning gas.

Further consideration should be given to the shortening of the battery's lifespan by forcing more battery cycles. I believe this was the prime consideration for the EV button being deleted in the NA offering. It was deemed necessary to enable providing the required 15-year warranty.

Those are some of my thoughts having had an EV button as standard fitment from the get-go.



* The true speed is shown on the vehicle signal check screen and is displayed in km/h. The displayed speed for that threshold is 42 km/h.