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OBD1 codes without dash light

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  • OBD1 codes without dash light

    Running better now that both banks of injectors are working but still rough idle. I donít have a dash light but do have a diagnostic port installed under hood. I know I need to connect a jumper wire between two wires but can I connect a test light to one of the wires to mimic a check engine light?

  • #2
    i think what your going to have to do is find the check engine light wire on the ecm and use that to hook a test light to. pin A and B of the diagnostic port need to be jumped, its basicly just grounds the self check wire. those will not flash a light.

    myself, id use this as a chance to wire in a check engine light, its something you should have, you never know when you might need to check codes in a hurry.


    • #3
      Thanks for the help and I'll be adding a CEL tonight. I used a probe type test light but having a dash light will be much easier.

      I got codes 14,15 and 54

      Also, I noticed the thing pictured below (attached to throttle body) is making a strange noise when the ignition is on. It may be making the noise when it is running also but I can't hear it due to engine noise. It sounds like a small electric motor with something loose inside making a dull thumping sound.

      Time for more research
      Last edited by 63a16p; 03-04-2018, 07:35 PM.


      • #4
        It appears you need to start checking your electrical circuits. Start with the ECM/sensor grounds. You are having trouble with injectors (previous thread), engine temp sensor (faults 14, 15) and EGR (fault 54). Also the IAC (pictured) is an issue.


        • #5
          After checking the wiring for the temp sensor, i realized the PO installed a single pole temp sensor in place of the dual pole temp sensor that should be installed. I'll get the correct temp sensor and wiring pigtail later this week and install. That should clear up the codes 14 and 15. I don't have the EGR parts installed so I'll live with that one until I can start modifying the chip to disregard the EGR. I have a Moates give to modify the OBD1 chip but want to get it running OK at a baseline before tackling the chip burner.

          Should the IAC valve make any noise? I'll probably grab another one from pick n pull just to have another for comparison.


          • #6
            You shouldn't be hearing the IAC under normal circumstances.


            • #7
              Replaced temp sensor with correct type and added a grounding strap from the engine to the body and to the battery neg. idles much better now but still a little rough. The engine hasnít run for about 3 years so the ECM may still be learning after being disconnected so long. Iím wiring a check engine light tonight so pulling codes will be much easier.

              thanks for all the help