On gassers, the CPS provides critical reference timing for spark and fuel delivery and causes intermittent cutout/no starts when it begins to fail.

On our diesels, that sensor provides some emissions data and the input to the tach. I don't remember anyone replacing it? Mines OEM at 272k.....

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)