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94 accord ECU, battery light on

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    94 accord ECU, battery light on

    I'm working on 94 accord, and about two days ago I was called and the person was complaining that the D4 light was flashing and transmission was having issues shifting, hard starting or not starting, (cranking but no fire) I went over and pulled code, got code 14 for D4 and nothing for CEL, either solenoid issue or FAS link problem between TCU/ECU. After doing some more diagnosing I couldn't find a problem, and did a battery power cycle, car behaved and ran fine.

    The next day the battery light was working intermittently then finally came on. Checked the fuses, they were good, ecu, 100 amp battery/alt fuse. I figure the alternator was bad, confirmed no charge voltage, hanging at 11.8 swap out alternator and charged battery in the mean time. New alternator in, battery light still on, no charge voltage, fully charge battery at 12.8. Swap battery from my 95 accord in, same problem. Shook cables, and checked grounds nothing. Removed green plug from alternator, battery light goes out. Did the same on my car to compare and the light stays out.

    I pull the ecu and noticed carpet is wet and water pooling in the cabin below A/C evap box. I pull the ecu out and I open it, and I can smell rotten fish or dead fish smell especially in one area of the ecu near the connectors, I can see a trace is burned, I hit it with electronic cleaner and the smell went away. I hook it back up and the car starts doing its crank but no fire for several tries, eventually fired up. As it was running that rotten fish smell came back pretty strong from the ecu, until I turned it off.

    To me this seems to be a wonky ECU going bad due moisture or water damage.
    I can take photos but it will have to be when I get it home and under better light.

    #2
    Re: 94 accord ECU, battery light on

    90's honda ecu's are known for bad caps - specially a big one near a big fat diode.
    i dont care that they are ncc's - change them.

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      #3
      Re: 94 accord ECU, battery light on

      End up being bad alternator, rip the one out of my car and tested in 94.

      Can't buy decent shit these days.

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        #4
        Re: 94 accord ECU, battery light on

        Well new alternator in, after an hour or running idle, grayish smoke coming from alternator along with what smells like electronics burning, then the battery light came on.

        I think the ECU fried that alternator as well, since no fuses were popped.

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          #5
          Re: 94 accord ECU, battery light on

          What alternators are you buying?

          Before you throw another alternator at it, check your battery. A bad battery can kill an alternator. O'Reilly and probably other auto parts stores offer this service for free. They can test battery in car in some cases you'll have to bring it inside for a complete test & charge.

          At O'Reilly the other day we had a customer come in for the free battery & alternator test. The portable tester could not test in the car since the battery was not charged enough. The vehicle would start (but cranking was very weak)... upon starting the alternator was literally singing loudly (and also failed alternator test). They had just come from their mechanic who had replaced alternator. This was a 90s Toyota IIRC so IDK how old the previous alternator was... anyway they removed battery from car and brought it in... within 30 seconds of starting a test & charge the machine spat out bad cell or something like that. After installing new battery vehicle started perfectly and alternator was quiet and passed the test.
          Last edited by shovenose; 09-19-2016, 04:35 PM.

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            #6
            Re: 94 accord ECU, battery light on

            open your ecu and check for leaking caps.
            if it's OBD1 then you have a 50/50 chance of finding bad caps.

            Comment


              #7
              Re: 94 accord ECU, battery light on

              Originally posted by shovenose View Post
              What alternators are you buying?

              Before you throw another alternator at it, check your battery. A bad battery can kill an alternator. O'Reilly and probably other auto parts stores offer this service for free. They can test battery in car in some cases you'll have to bring it inside for a complete test & charge.

              At O'Reilly the other day we had a customer come in for the free battery & alternator test. The portable tester could not test in the car since the battery was not charged enough. The vehicle would start (but cranking was very weak)... upon starting the alternator was literally singing loudly (and also failed alternator test). They had just come from their mechanic who had replaced alternator. This was a 90s Toyota IIRC so IDK how old the previous alternator was... anyway they removed battery from car and brought it in... within 30 seconds of starting a test & charge the machine spat out bad cell or something like that. After installing new battery vehicle started perfectly and alternator was quiet and passed the test.
              I had junkyard one in there and now a reman one from advance auto on second replacement. All three bit the dust less than an hour of operating. Second time I swapped the battery from my car into the 94 to eliminate battery as issue. The battery that came with the 94 was a duralast, but the battery in my 95 is interstate, I know that battery is not bad since I use it every day.

              Originally posted by stj View Post
              open your ecu and check for leaking caps.
              if it's OBD1 then you have a 50/50 chance of finding bad caps.
              Already opened, no visually leaking except dark traces on pcb.

              I noticed temperature discoloration on wires to green plug for alternator to ECU but no discoloration on main charge cable. It's not blowing fuses. I think ECU has got a short in it and it smells like a rotten fish every time it's powered up.

              Also car took several cranks before firing up, I couldn't hear the fuel pump run, But few moments later I heard the fuel pump run... Fuel pump is handled by PGM-FI relay under the dash which is controlled by... the ECU!
              Also car flashed D4 light, I turned it off/on, it went away but the oil light came on and blinking randomly, turned off/on it went away too.

              I had someone sit in the car while I man-handled the main harness that runs under the intake manifold, that's where alternator wires and oil sending unit and transmission harness run through to fuse box on passenger side and to dash harness on the driver side, so if there was a problem it should have shown up.

              I think this ECU is fucked, it's spitting out random shit and frying the voltage regulator packs on alternators, intermittently running the fuel pump.

              I will swap ECU tomorrow and get another alternator, if it fries too then I don't know what to say.

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                #8
                Re: 94 accord ECU, battery light on

                rotten fish / cat piss = electrolyte.
                so you DO have atleast one leaking cap.

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                  #9
                  Re: 94 accord ECU, battery light on

                  replace ALL lytics.clean board thoroughly.look for eaten traces or carbon tracking.

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