Hondata

1990 Honda civic hatch
k20a
kpro-14016. PRB Version 4.4.2.0
purchased from humble? 5 years ago
wireworx milspec race harness
electric water pump/alternator relocation. Alternator housing has independent grounding. All oem grounds in correct locations.
2005 civic alternator (new)
New battery

While running voltage reads 14.1 at the battery, 14.28 at the alternator, but battery voltage on display fluxuates all over from as low as 11.7 to as high as 13.5. All harness wires added to chassis are tapped in to oem harness locations via oem honda plugs.

Most cases this issue has to do with something wired incorrectly in the harness. I would recommend that you try the ECU in a known working vehicle and if the voltage is stable you will have to start going through your harness to find where the problem is. It could be how the Oxygen sensor is wired in.

Ok. I guess I will have to do some pin testing from the o2 diagram first. I had an issue with how this thing was wired when i first got it and sent it back once i found the issue because i didn't have the tooling to repair it. hopefully its not a repeat scenario.

Thanks to the helpful suggestions I was given here, problem solved. Sensor was pinned wrong. After correcting that, battery voltage is steady, no breaking up in any rpm. Thanks again for all involved in my solution!!

any pinout for the oxygen sensor?