Originally Posted by Tipton103
Really a alternator can cause that that's a new one to me then last thing I would have changed
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The defective alternator is generating EMI which interferes with the CPS. The CPS is basically an electromagnet which picks up the teeth on the disk and generates a pulse back to the computer. It's very sensitive to EMI.
Have your alternator checked out at Autozone or similar before replacing. it as there are other causes and alternators aren't cheap.
It's a weak or defective diode that causes it. Sometimes you might also hear a whine in the radio that changes pitch when you rev the car.