Sunday, May 24, 2009

P0097, A Miata Success Story

I must say my ScanGauge II OBD-code reader has paid for itself;  I've used it---in conjunction with the internet, of course---to solve another ECU-related issue with Mia, my Mazdaspeed Miata.

Over the last few days, the check-engine light began illuminating intermittantly, principally when acccelerating and turning simultaneously, as when pulliing away when you get the green turn arrow you've been waiting for.  The CEL has usually been accompanied by mild hesitation of the engine.  Today, Mia threw the code repeatedly.  Each time, the code was the same:  P0097.  After I got home, I went straight to, the forum dedicated to my exact car.  It turns out that P0098 means, to paraphrase, "intake-temperature-sensor voltage too low," and this code is frequently reported on the MSM.  It seems that the wiring to the intake-temp sensor rubs against the edge of the sensor housing anytime the engine moves, which can cut through the wiring's insulation, shorting of the signal.   That sounds like it could be what's going on, I thougt, and headed out to check under the hood.

Sure enough, the intake-temp sensor's housing is hexagonal, and its edge has a clean, 90-degree angle.  The sensors leads are insulated, but not physically protected from the housing against which they rest.  The signal line---I believe it was the signal, rather than the ground---was worn down to the conductor.  I wrapped each line in electrical tape, then wrapped the two lines together.  A quick spin in the car verified that I had indeed fixed the problem.  

It makes me happy to repair a twentysomthing-thousand-dollar* car with 10 cents worth of electrical tape.

* MSRP, not what I paid.

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