I just got rid of my 2006 Jag S Type but a few years ago I’d go out to start it and get pulled out of the garage and a red engine light would come on and it would die. Not the check engine light but a light that meant you’re in deep kimchee. Mechanic told me it was the mass air flow sensor. I finally took it to the dealer and they couldn’t figure out what was wrong with it but said no, not the mass air flow sensor. Finally a couple of days later they call me and guess what it is? Friggen battery! Yep, the battery was getting ready to go and was causing the error code that everyone thought was the mass air flow sensor.
Makes me long for the old days when the cars didn’t have all the electronic crap. My cars lights came on, all of them, flickered car died, barely ran. After a week in the BMW shop they said it was a bad tire pressure sensor gauge around $250. Frankly, I prefer to visually inspect my tires and if one is losing air I can sense it driving.
Yes, before my mech friend found the neighbor’s MAF defective, the neighbor had replaced the battery and the alternator. The voltages were good, steady.
All of the computer and control sensor circuits require a steady 5V which come from battery and alternator. Voltage regulators in the electronics should be keeping a constant 5V but volt regulators can go erratic over time especially with a degrading battery or alternator.
The bigger picture I see is that computers, computer circuits, computer sensors, placed on automotive engines can help fuel and emissions issues BUT ...
by placing such systems on an automotive engine and drivetrain, IT INTRODUCES LONGER TERM SAFETY CONCERNS.
My engineering brain tells me that automotive engineers should design a bypass of all electronic controls FOR SAFETY PURPOSES.
If a situation arises where a vehicle system is IN BYPASS meaning the system has determined the computer control system has a fault, then a design can be added to turn on a light inside the dash display and turn on a flashing light outside. This allows the driver to drive safely while getting the vehicle to a shop to investigate the electronic control system.
To have a vehicle shut down in hazardous conditions because of electronic malfunctions or conditions IS INTOLERABLE and especially when those systems exist to control fuel and emission performance which is a noble goal but which is secondary to safety.
Safety comes first.
I am informed that a ‘LIMP ALONG’ system is sometimes included in these control systems meaning that the vehicle can be driven a short distance but that this is related to security and not fuel/emissions and which does not resolve the safety concerns.