As a theft deterent I wired a remote switch into the fuel pump fused supply. So a fuse jumper in the fuse box with the fuse on the secondary position, a feed and return wire to the switch and the return wire into the original fuse slot. This works as it should switch in off position engine does not start. So far so good but now when the engine starts I get a warning "check engine" and the engine light comes on. Remove fuse jumper and replace the fuse all OK with no warnings. Any suggestions? Oh its Fiat Ducato based Swift 604 2017 build