Why does my car's ECU have Alzheimer's?

Asked by Aug 11, 2014 at 10:03 PM about the 2007 Hyundai Accent GS Hatchback

Question type: Maintenance & Repair

The check-engine light has come on recently due to a different (presumably unrelated)
problem with the engine, so I take it to a mechanic. Mechanic calls me up and tells me
there are a few problems -- the first is the reason is the misfiring engine, and then he also
notes an error reported from the check-engine readout about my oxygen sensors. Which
leads him to a third, more sinister problem: Every time he turns the car off, the ECU or
whatever is responsible for keeping track of system problems (and signaling them in the
form of a check-engine code readout) keeps rebooting every time the car turns off.

That's not good. I'd like to know if the other issues with my car are occurring together --
maybe they are symptoms of a larger problem, for instance. The computer is supposed to
record and monitor whatever problems are tripping the check-engine light, but I notice that
every time I turn on the (still not yet fixed) car, the check engine light is OFF. Then it's
like the car suddenly remembers it has a problem, and only after about five or ten
seconds of idling does the dashboard signal a problem.

3 Answers

105,335

Your loosing the KAM in the ECM, this can be caused by a couple of things, check the ECM's power supplies, make sure you check them all, a good old fashion test light will work for this, then make sure all of the ECM grounds are good, checking all of the chassis grounds would be a good idea this point, an ohm meter works for this, if you haven't found it by now there could be a failure in your ECM. A good wiring diagram would really help in this operation.

2 of 2 people found this helpful.

OK, I need to obtain a multimeter and wiring diagram. BTW I'm new to this whole fixing a car thing, my (first and only) car has been running strong for 85K miles, it's gotten me all the way across the country and all I've ever done is change the oil, routine maintenance, and install my own radio.

105,335

It would be a good idea to get a complete shop manual like a Mitchell or a Factory one, steer away from Clymer or some of the cheaper ones. I have had some good luck using EBay, most of them were on CD's or DVD, DVD's have been the best. FYI and good luck.

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