OK, so today I had a switch installed in my ashtray to interrupt power to the PSE so that I could choose to have PSE operate as stock, or to be loud all the time throughout rpm/speed range and without regard to settings.

Problem is that it kept throwing a check engine warning (and didn't seem to work very well, either).

Luckily, I had them install it so that I could reverse it very easily (i.e., unplug the switch and bypass).

With the switch out, it does not throw check engine light codes any longer.
What are potential causes for this? I thought that cutting the power was an easy hack that should not have any impact on check engine lights.

Thanks.

 

Try this:

Disconnect the orange plug in the engine compartment and see what happens.
The PSE should always be on loud and you should not get a check engine light.

If everything is OK that way, check if they spliced the switch into the right wire .
(the one going directly to the solenoid valve )