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  • Probability of code P1651 being PCM related?

    Alright, since when I bought the car last year, the car always had the ses light on. I bought a scanner to see what codes were, and the only one that I would get is P1651, which states something like "fan relay #1 Control Circuit" on my scan tool. After searching the internet for any leads, i found the usual check wiring, relays and other basic fixes, which didn't solve the problem. I installed my own manual switch for the fans which works just as expected with a hi/off/low setup. This makes me think that the wiring is fine on the power and relay/ control side, leaving the PCM as the last thing to check. What do you guys think?

  • #2
    Couple things:

    1) did you try replacing the fan relays?
    2) if yes to above, did you try removing the fan relay and jumping the power with a wire to eliminate faulty relays?
    3) do both fans not turn on if you command them or only one?
    4) did you try pulling the fans and jumping power to the motor directly?

    I believe the fans are wired a little wonky. I vaguely remember going through an issue on my ls1 that gave me headaches and caused me to be swapping relays around until I determined 1 fan motor had gone bad on me.

    With a fan switch you are bypassing relays and wiring are you not? If both fans work with your switch installed then have your problem is likely from before you have spliced into the the fans back.

    Have you ruled out corroded terminals at the relay box?


    2002 SOM Z28 Camaro - 12.9 @ 104 mph
    1996 3800 Camaro - 13.43 @ 100.77 mph


    Project Cars | How To Guides | Scratch Repair | Synthetic Oil

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    • #3
      Ok, i finally had sometime to wrench and here is what I found
      1. I switched around all the existing relays within the car and there were no different results with any of them
      2. jumping the relays with a wire turned the fans on as well
      3. if you mean with the manual switch, i can get one, or both, fans to turn on
      4. both fans spin up fine with 12v applied
      The way I wired up my switch is by forcing the relays to ground out, thereby turning on the fans (just like Shoe box's and Firebirdgt's method). I really don think that the fans can be blamed here... the last thing i could try is to pull out the wiring harness, but I don't have any other electrical problem at the moment, so I really don't want to pull it out.

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      • #4

        Unfortunately, I found my problem... the pins in the PCM became corroded and one pin in particular actually broke off and is now lodged in the connector. how can I clean that out now?

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        • #5
          Wow, their in pretty bad shape, I would get another pcm and harnesses. About all you can do to save it. I never seen one that bad, but I live in AZ so don't get bad weather or stuff rusting. Lets see what others say about it.
          08' L76 6.0L 4X4 Chevy EXT.Cab LTZ Vortec MAX with Snug top cover, Dynomax exhaust,Hptuners& K&N intake
          96' Camaro M5 to A4 conversion, alot of mods ,see Homepage. GT35R Turbo http://www.cardomain.com/ride/244123...vrolet-camaro/
          https://www.facebook.com/steve.starcher.18

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          • #6
            Are you missing a seal on that pcm connector? Water is getting in there and corroding that out. Only a matter of time until you likely have some more issues.

            A paper clip can be used to pop the connectors out if I remember correctly. You could try popping them out and even taking a pic of the connector pin and go to a dedicated electronic surplus store to see if they have them. If they do I would clean it if you can, or snip the wire as close as you can to the connector and replace it with a new one and put it back together.

            I would also check junkyards and car-part.com for another harness as it may be less of a headache to replace it.

            If you can grab one for 20-30$ it may be worth it. That being said the harness is routed snaked around the whole engine.

            2002 SOM Z28 Camaro - 12.9 @ 104 mph
            1996 3800 Camaro - 13.43 @ 100.77 mph


            Project Cars | How To Guides | Scratch Repair | Synthetic Oil

            Comment


            • #7
              A soft wire brush may help clean the terminals

              2002 SOM Z28 Camaro - 12.9 @ 104 mph
              1996 3800 Camaro - 13.43 @ 100.77 mph


              Project Cars | How To Guides | Scratch Repair | Synthetic Oil

              Comment


              • #8
                Hmm... there is one seal per connector already installed on the harness connector , so i should at least replace them. the harness seemed to be in good shape, so I took it apart and cleaned it with alcohol and a small brush it hardly seemed to have been damaged by the same corrosion. The PCM, on the other hand, is junk, so bye-bye 96 PCM and hello 97 PCM. The last thing on my to-do list would be to buy or borrow HPTuners and change the fan temperature parameters.

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                • #9
                  With Hptuners you can also delete the code, you already have a fan switch so you should be good.
                  08' L76 6.0L 4X4 Chevy EXT.Cab LTZ Vortec MAX with Snug top cover, Dynomax exhaust,Hptuners& K&N intake
                  96' Camaro M5 to A4 conversion, alot of mods ,see Homepage. GT35R Turbo http://www.cardomain.com/ride/244123...vrolet-camaro/
                  https://www.facebook.com/steve.starcher.18

                  Comment

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