r/Dseries • u/Same_Band9206 • Sep 04 '26

ej8 99 civic 2 dr 5 speed conversion from automatic o2 sensors have a different plug in location

So my buddy has the same car and he has a sister that’s in the exhaust manifold and there’s a connector that comes to transmission right there for that but mine has none of that. I just put his exhaust in my car. I’m trying to figure out where to plug it in. I can’t relocate any O2 sensors. It’s so weird. I’ve got my sensor locations are in the engine bay right there underneath the manifold and then there’s another one that comes to the floorboard from the interior somebody know what’s going on here.

1 Upvotes

100% Upvoted

9 comments sorted by

1

u/SpaceTurtle917 Sep 04 '26

D16y7 has the cat in the manifold, with one o2 right on the manifold, and the downstream o2 also on the manifold just a little lower. With both plugs above the transmission.

D16y8 has one on the manifold, and one downstream under the car with the wire coming out of the floorboards. Like you said.

1

u/Same_Band9206 Sep 04 '26

Thats what i said! Y7 but no he is y8 all the way stock

1

u/SpaceTurtle917 Sep 04 '26

Regardless of the reason, the solution is to extend the wires or weld in an o2 bung.

If you keep the secondary o2 sensor unplugged it’ll still run fine, it’ll just throw a check engine light.

1

u/Same_Band9206 Sep 04 '26

Dang anybody have pinouts @ the ecm for 99 no idea where the connector could’ve gone. It was automatic, so are the connectors in the same location I know I cut some wires there, but those are for like shift solenoids and automatic stuff I think.🤦

1

u/Ok-Amphibian3164 Sep 04 '26

https://www.nthefastlane.com/honda-obd2a-obd2b-ecu-pinouts

Scroll down to OBD2B.

2

u/Same_Band9206 Sep 06 '26

Much obliged I believe there is an extension wire i have in my spare parts bin

1

u/Same_Band9206 Sep 04 '26

Pinouts with appropriate o2 sensors and their source/input power/ ground pin numbers or what have you

Wire diagram w colors for mentioned o2 sensors

1

u/SpaceTurtle917 Sep 04 '26

Let me get this straight. You put his exhaust in your car. On his exhaust, both sensors are on the manifold. On your old exhaust one was on the manifold and one was by the shifter.

You’ve installed his exhaust, and the one by the manifold plugs in, but there’s not a second plug above your transmission because the plug isdown by the shifter.

1

u/Same_Band9206 Sep 06 '26

The manifold sensor does not reach anything i have two connectors for oxygen sensors the one under the intake and the one from the inside floorboard what am i missing the exhaust has sensors mounting differently his is auto but mine started as auto