I don't profess to be anything like an expert here but I've had a bit to do with vehicles with EFI. Normally on an old system, say you disconnect the airflow sensor or coolant temp sensor, it'll just stop. On newer cars, you do the same thing, the motor keeps going, maybe not as good, and on comes the check light. You take it to your dealer/workshop, they scan it and that'll indicate the fault.
My car was running poor, not totally undrivable, so upon noticing the temp guage reading cold, I thought the thermostat might be stuck open, not the case, the engine temp was around 85-90 by my temp gun. Next I thought, temp sender unit for guage. So after not finding it in any normal place, I checked the w/shop manual/wiring diagram. Same unit does both, so I though I'd disconnect it to see if it would alter the running by going into a LHM, this didn't happen, it started running super rich to the point the even holding the throttle on it just smoked to a halt.
Fast forward a week. Got a new sender unit and after much cursing of the dick brain who decided to put it in the dumbest place ever, got it fitted and it runs fine now. That's how I concluded there wasn't a LHM on my car, cause it didn't limp home, it just turned up it's heels and played dead.
you just won't have an SPI any more...!
