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  • New CJ7.... trying to sort out the mess

    Just got the jeep that I have been waiting 12yrs for and now I am trying to figure out error codes. It has a gm 4.3 that was "rebuilt" the check engine light comes on intermitently and I need to know why. This is just the first of many issues but I think is the most important.

    I was looking into code readers but can not tell where to start as I am not sure what ECM is in there

    Any help would be great.

  • #2
    4.3 engine? Check engine light on a CJ.?????????? Make me smart. I'm confused as usual.

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    • #3
      if theres an autozone nearby they check em for ya for free...don't let em sell ya anything yet though...an intermittent light can be a multitude of things sometimes, especially on a transplanted motor like your GM 4.3L
      Last edited by the Captain; 07-26-2008, 12:21 AM.

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      • #4
        Originally posted by redtail View Post
        4.3 engine? Check engine light on a CJ.?????????? Make me smart. I'm confused as usual.
        It's swapped in. The 4.3 is an EFI engine, so it has a check engine light to keep the computer systems happy.


        Kosh: The engine is likely an OBDI engine since OBDII systems are more expensive and held to be more difficult to swap. A GM dealer may be able to help you determine the year of the engine. The ECU is likely tucked under the dash someplace. Try a small mirror rather than inverting yerself under the dash...unless you are a contorsionist and like pain and headrushes.

        OBDI systems use brand-specific (Chevrolet/GM) code readers that are quite inexpensive. You can get an OBDII for around 100 bucks if you have that system. The readers for each will NOT read the other type unless you have one of the REALLY spendy units (like 1500 bucks). If you can find the port, you'll have it made. The shape of the port will generally tell you what ya got as the OBDI and II ports are different.

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        • #5
          Post a picture of the engine here and I can tell you if it is OBDI, or OBDII.

          Like Gryphon said it is most likely OBDI as those are the easiest swap. Assuming it is OBDI...

          To read the codes all you need is a paper clip.

          1. Turn the key to the on position, but don't start the motor.

          2. Use the paper clip to short the diagnostic terminal to ground. (Short the far right terminal on the top row of the diagnostic connector to the terminal next to it)

          3. The check engine light will start flashing. It will always start out flashing the diagnostic code (12) so it will flash once, pause, then flash twice. It will do this 3 times, then it will flash any codes stored in memory in the same manner, repeating each code three times before flashing the next code. For example, code 13 would be one flash, pause, three flashes. Code 43 would be four flashes, pause, then three flashes.

          Buy yourself an older Chilton's manual for the S-10 blazer series if you can find it. (assuming it is TBI) The older manuals have a lot more and better info than the newer ones. (Chilton's just sucks since Haynes bought them out)
          Last edited by tracraym; 07-27-2008, 11:55 AM.

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          • #6
            went to partsource (cdn) and they can not pull a code because they/I do not know the year of the engine.

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            • #7
              Just did the paper clip and all I get is 12 over and over again

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              • #8
                You have a TBI engine, which will be OBDI compliant.

                Sounds like you may have an intermittent problem that won't set a code in memory (or the PO did the swap incorrectly and turns off power to the computer when the key turns off and thus erases the memory).

                The good news is, if the malfunction is not bad enough to set a code, then fixing it can be put at the bottom of the to-do list. The bad news is, the only way to find out if the computer is wired correctly is to start tracing the wires from someone else's' swap

                Try this:

                run the motor until the check engine comes on, then shut down the motor without turning the key off (pull the coil wire, wear gloves). Then read the codes again and see if you get a code. If 12 is all you get, then put the problem down as an annoyance instead of a must fix. If you get a new code, turn the key off, wait a minute or so, and then read the codes again. If the code goes away, you will be chasing someone else's screwup. If the code sticks around, then you have a new code to start troubleshooting.


                As for the parts store, look at the throttle position sensor connector on the throttle body. If it a small roundish 3 wire connector, tell them it is a '92 S-10 blazer. If it is a large (approx 1" x .25") "weather pack" connector with three separate round connectors inside an oblong housing, tell them it is an '89 full size pickup.

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                • #9
                  so you were right about the power going off to the computer. I did manage to get a code after stopping the engine. It was 12 then 24 then 12 again. Turned power off and then back on and the code had cleared.

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                  • #10
                    Just thought that I would post the answer for any one searching in the future. I am guessing that there is not a speed sensor hooked up to the ecm as I still have the t5 trans and the spedo (although incorrect because of tires) is attached to the transfer

                    Thanks for all the help.

                    Code 24
                    2 flashes, pause, 4 flashes
                    Vehicle speed sensor signal showed less than 3 MPH for 2 seconds when engine speed was greater than 3000 RPM and transmission has not been in park or neutral for more than 4 seconds. Or vehicle speed goes from above 18 MPH to 0 in less than 2 seconds without applying brake. This code can only appear when the vehicle is in motion, if it appears when the car is not in motion, ignore it. Check ECM connections, any other problems should be diagnosed by a qualified mechanic.

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                    • #11
                      they have an adapter speed sensor for the dana xfer cases... in fact there was a guy on our local craigslist that was selling his for the d20/d300 cause he was parting out his jeep project...

                      if you want to fix that, you may want to look into it.. I think that Advanced Adapters sells them....

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                      • #12
                        Another option is to ground the park neutral switch lead from the ECM. This tells the computer that you are in park all the time and it stops looking for a speed sensor signal. (That is what I will be doing until I get the speed sensor setup installed.)

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                        • #13
                          Originally posted by kosh View Post
                          Just got the jeep that I have been waiting 12yrs for and now I am trying to figure out error codes. It has a gm 4.3 that was "rebuilt" the check engine light comes on intermitently and I need to know why. This is just the first of many issues but I think is the most important.

                          I was looking into code readers but can not tell where to start as I am not sure what ECM is in there

                          Any help would be great.
                          i would advice trying to at least narrow down the cause of the problem, an error read code is really your only opinion, from there you can isolate the problem and solve it

                          http://jrbrahamas.info/adver.gif

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