310civicEX

i put a vtec motor in a 2001 lx .. has a header with 2 bungs.... the top hole (upstream) has an 02 sensor with a grey connector at the harness... its only throwing 1 code p0141 downstream 02.. but there is litterally knowhere to plug it in (downstream) 02... the EX has the 02 connector near the firewall..this LX does not have that one, for some reason this LX only has the one connector near the thermostat housing. does anyone have any info on where the downstream 02 p0141 plug into the harness?

310civicEX

/\ this guy changes the upstream ( blue connector) thats the one i dont have on my 2001 LX.... im confused because im not throwing an upstream code.. but i got the downstream connected..and im getting that code.. im wondering if the 2001 LX didnt come with a blue connector?

ezone

On a D17A1 harness, Both O2 sensor connectors are supposed to be together near the stat housing

You used the original non-vtec harness, yes? Not the harness for the vtec engine?

310civicEX

well its a A2 with an LX harness and an aftermarket header... the blue connector is noth on the harness at all... and i have the grey one plugged in and the upstream code went away.. but the blue MISSING one is upstream.. im so confused

Slumpertcivic

310civicEX

its an LX harness

ezone

LX non-vtec harness......
Sounds like connector for sensor 2 might have gotten misplaced, tucked back in a spot and forgotten when the engine was replaced.

Follow the existing sensor connector to the main engine harness and look there for the branch that leads to the "missing" connector..

310civicEX

is the blue connector in the same wire group with the gray one? as pictured... or does that one plum from somewhere else?

ezone

Both should 'branch' out of the main harness at the same location IIRC
(they both have to end up in the same spot, so it makes perfect sense they both come out of the harness at the same spot)

I have a diagram that shows both harness connectors for front and rear sensors should be gray ...... blue was not used on the early cars

Slumpertcivic

ezone

The CAR already had the header in it? Did it ever have a rear sensor since the header install?

310civicEX

No 02 plug at the firewall ex location...
only one plug in front at the no-vtec location..

is it possible the early 2001 civics only had one 02? Also the vtec plug is there and it is plugged in..the owner said they put a ex harness in..

Slumpertcivic

ezone

Impossible.






EX engine harness? That changes everything.

Congratulations, you have a homesick a****ion. The connector for the rear O2 sensor is not part of the engine harness.

310civicEX

wait.... so the downstream 02 connector is NOT part of the harness? where does it plug into then? lol

Colin42

Underneath the shifter it sticks into the middle of the cat on the OEM setup

310civicEX

do you have a picture of it?

Colin42

Nope, you'll have to slide under and see what's there. Might have to get that harness from the junkyard.

310civicEX

My trans tunnel and firewall areas show no sign of downstream 02 sensor connector .. but up from only has one 02 plug

Colin42

Looks like a junkyard trip is in order then

ezone

The LX car doesn't have what you want.

The EX rear sensor connection comes from one of the dashboard harnesses, but they use different dash harnesses, the harness in the lx car is not prewired for it

The wires for the rear sensor are not in the same places on the different PCMs either