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  • #1

    Service Engine Light?

    A couple years ago the check engine light came on in my car ('02 GT). Code reader said it was the cam sensor. Ended up being a bad diode on the alternator even though it was showing good. At that time I found a used alternator on here from a board member which fixed the problem. Does anyone have one laying around they want to part with that they know is still good (No check engine lights at the time it was taken off)? I'm going to go ahead and replace the cam sensor since a cheap part but figured I'd ask in case it doesn't fix it. I'll be in the Carrollton area this weekend.

    Thanks
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  • #2
    That's an odd reason for a cam code to pop up.

    What's the explanation behind that?

    A diode just keeps current flowing in one direction, but in an alternator they are used convert ac to dc.

    I understand the sensors are voltage referenced, most at 5v. I guess a bad diode was messing with the system voltage? Seems like more codes would be present.

    Odd, maybe when you replaced the alt, you unhooked the battery and cleared the code and it took this long to fault again. < my guess.

    320rwhp. 7.67 @ 90mph 1.7 60'

    DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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    • #3
      Nope, a bad diode or regulator in the alternator can cause interference with the cam sensor. Very typical of the late model mustangs. I had the same issue. My car kept popping a CEl for cam position sensor and then my battery died. Swapped the alternator, replaced the battery, and the code went away.
      01 red GT - 745whp/780wtq Whippled 4V and built 4R75W

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      • #4
        Originally posted by 91CoupeMike View Post
        That's an odd reason for a cam code to pop up.

        What's the explanation behind that?

        A diode just keeps current flowing in one direction, but in an alternator they are used convert ac to dc.

        I understand the sensors are voltage referenced, most at 5v. I guess a bad diode was messing with the system voltage? Seems like more codes would be present.

        Odd, maybe when you replaced the alt, you unhooked the battery and cleared the code and it took this long to fault again. < my guess.
        Yeah I thought it was crazy too but after I had a customers car we replaced the sensor and same code came back on, I called around and was told the same thing. I replaced the alternator and it stayed off. I have done at least 5-6 99 up mustangs for the same code and alternator every time.

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        • #5
          Originally posted by Fastlane View Post
          Nope, a bad diode or regulator in the alternator can cause interference with the cam sensor. Very typical of the late model mustangs. I had the same issue. My car kept popping a CEl for cam position sensor and then my battery died. Swapped the alternator, replaced the battery, and the code went away.
          This is basically how it was described to me while trying to figure it out after replacing the Cam sensor the 1st time and the code coming back. My battery never did die last time but I don't remember letting it go that long before we figured it out was the alternator. In fact I just replaced that battery a few weeks ago after it let me down. 8 year life on an optima yellow top on an everyday driver. Replaced with the same thing hopefully this one will last 8 yrs.

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          • #6
            Originally posted by 91CoupeMike View Post
            That's an odd reason for a cam code to pop up.

            What's the explanation behind that?

            A diode just keeps current flowing in one direction, but in an alternator they are used convert ac to dc.

            I understand the sensors are voltage referenced, most at 5v. I guess a bad diode was messing with the system voltage? Seems like more codes would be present.

            Odd, maybe when you replaced the alt, you unhooked the battery and cleared the code and it took this long to fault again. < my guess.
            A blown diode allows the current to flow in an AC pattern, which causes some of the current flowing in the reverse direction to interfere with what the PCM sees from sensors. It just so happens that it is usually the cam sensor in the 99-04 (maybe newer, I don't know) that catches the interference and throws a code.
            كافر

            Originally posted by sc281
            Always better to be an Uncle than a Father. All the fun stuff and none of the expensive stuff.
            Originally posted by Trick Pony
            ...from what I've seen on here bcoop knows his shit when it comes to smoking meat.

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            • #7
              I see, that's for the tip. I'll keep that in mind for later.

              320rwhp. 7.67 @ 90mph 1.7 60'

              DD: 2004 GMC Sierra VHO 6.0 LQ9 324whp 350wtrq

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              • #8
                Rfi, it can be a bitch

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                • #9
                  Originally posted by shumpertdavid View Post
                  Rfi, it can be a bitch
                  This.

                  It's also why we can't run solid core spark plug wiring, which would be a major improvement to efficiency.

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