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Apparently there are other reasons why the Maintenance Light can blink besides oil change intervals. And it says NOTHING about this in the owner's manual or repair manual, which I have checked. The light suddenly blinks 5 times while the vehicle is being driven with the headlights off or when the headlights are turned off. And the behavior will repeat even if you reset the light using the odometer button. I would assume the vehicle's maintenance warning system can detect other maintenance issues besides needing an oil change. Any idea how to interpret this behavior?

 
Rep Power: 118

By other reason you mean a failing MICU or a dead ground?

Any time someone mentions something with the dash changes with lights on/off we can usually track it back to aftermarket radio install and “hooking” up the factory illumination wire to anything..

 
Rep Power: 517

The maint or maint req'd light is ONLY a mileage counter. Nothing else. You could rotate the tires or change your underwear when it comes on instead of changing the oil, it doesn't know or care.

If it's blinking at completely wrong times I'd expect the gauge cluster is failing. Does self test show problem?