driftrx7

Whats up guys..

I have searched all over the net.. still have no resolution.

I'm having problems with this CEL.. i have a P0131 code i cant get rid of.. the car is bone stock minus some aftermarket headers. Now here's where it gets weird.. i get the CEL and i ordered a new denso O2s, i go to change it and i notice the previous owner had a long wire ran under the car to the back of the motor. so i pull the O2 out and i notice the plug is different. the old O2 had a female plug and new 1 had a male.. so long story short.. i cut the clips wired it up and still have the code..

so this is what i have done so far..

Tested voltage on the harness/O2 plug car side (getting 12+ volts blk/yel wire)
Tested ground on the harness/O2 plug car side (getting Ground (blk/grn wire)
There is wht/blk wire has no signal
There is a thick white yellowish looking wire has 5v

I hook up the wires according to denso color codes

blue=signal
white=ground
blk=heater
blk=heater

I also noticed the plug for this o2 is way in the back of the motor under the intake.. i found this weird because denso sold me a primary o2 with a really short wire and wrong clip.

I also changed spark plugs and fuel filter.. no difference.. Please any help is appreciated.. i need to pass smog test and i would like the vtec to work lol.

Former User

Are your wire splices soldered and heat shrink insulated?

Have you measured the fuel pressure and tested the FPR?

driftrx7

Actually i have not soldered the wires and heat shrink wrapped it. do you think that would be the cause??

Also, i will be changing the FPR tomorrow.. I have no tester available to use.. it would be easier to just swap the FPR cause my buddy has 1 laying around.. if that doesnt work.. i will look into getting a FP tester..

driftrx7

The other thing is.. which two wires should go to the heater??? is it the WHT/Blk and Yellow/BLK?? because I know the BLK/Green is ground.

there is 2 blk wires for the heater, does it matter which one it goes to?

Alexpro

Hey man, from my experience you never want to cut the o2 sensor wires...
Also you have 2x O2 sensors... on OBD2 so check if you replaced the right one...
(OBD II P0131 Oxygen Sensor Circuit Low Voltage =Bank 1, Sensor 1)

Common Problems that Trigger the P0131 and P0137 Code

* Defective Oxygen Sensor/Air Fuel Ratio Sensor
* Defective Oxygen Sensor/Air Fuel Ratio Sensor Heater circuit
*
* High Fuel Pressure
* Defective Engine Coolant Temperature Sensor
* Defective sensor wiring and/or circuit problem
* PCM software needs to be updated
* Defective PCM

driftrx7

Yes, i did replace the right O2.. It is the upstream O2 on the manifold. the car is a EX.

well the universals are always cut and people do have success with those..

Today replaced the FPR.. no help P0131 code came on minutes after i have reset the ecu with OBD scanner.

tomorrow i will solder and heat shrink the wires to see if that will help.

driftrx7

still need help!

Former User

driftrx7

OK.. I Finally got to resolve this issue with the CEL... here's what i did..

I was going to solder the wires, however a friend of mine had a new o2 so i decided to go with it.

I took out the Denso o2 sensor i originally bought.. and i replaced it with a Denso pn# 234-4733 o2 sensor.. it was plug and play and had the right female plug i needed.

The issue was the wires on the o2 were hella short.. I didn't want to cut it like the other one..
as some of you know on the 99-00 civics the plug for the primary o2 is on the back of the harness located near the intake manifold. I basically had to open the harness a bit and pull the plug toward the front of the car near the o2.

I loomed and taped everything back up and now over 200 miles later no CEL..

I hope this helps you guys out there.. Thanks for the help Ron and everyone else!!