I keep having these codes pop up related to o2 sensors already checked everything i could think of

Had damaged plug in o2 engine harness replaced that
Replaced both o2 sensors with denso replacements
Still throws a code p0141 or p0133
And at the same time the motor starts acting crappy at low rpms
Its leaning out and makes it very hard to shift shoothly since the rpm drops and jumps and makes for a rough clutch engagement so i look like a fn noob every time i start driving at the stop light

can the ecu curcuit get damaged from bad or failing sensor?

its a 2000 gsr integra with stock ecu and basic boltons

 

do you have any exhaust leaks near or before the front o2 sensor?
are you sure the new pigtail was wired on correctly?

usually when you get these codes its a bad sensor or bad wiring.

 

its not universal it came with a plug
and new engine harness have been checked over and over for any damage or backed out pins.

is there anything else that can be damaged that would cause this issue?
i had this with 2 engines 2 different engine harnesses and ecus
i cant see or feel any exhaust leaks i checked many times even pressurized theexhaust piping with compressor to check.
can the firewall harness get damaged from bad o2 sensor or if heater circuit is shorted out in the downstream sensor?
I'm not sure if it was the heater circuit but 2 of the wires were scraped and exposed and covered in oil. i replaced that but still same codes
and they are correct sensors for this year i checked by denso webpage


its just pissing me off now i keep thinking that its fixed and thenit just show up out of nowhere after a week or a month or 3 months of driving with no codes...

 

I'm having almost the same issue with my obdII Del sol.
do you have a cat on it?
Good fuel pressure?
Does it overheat?
Is your fuel filter good?
Those codes that it's throwing could be more than just a bad o2 sensor..

 

Motherf.....
All my ground points were corroded
25ohm at thermostat ground

I cleaned all of them last summer and measured with voltmeter

Never had ground points corrode so fast

Once i cleaned all of them o2 sensor code went away

 

Ok so that fixed it for a week barely
Codes are back
Randomly popping up switching between p0420 and p0133
Brand new denso sensors front and rear
And good cat
I can feel the power loss ar 1500-2500 rpm but only in first and second gear

 

It happends right before check engine light pops
It will run good for a week and then suddenly just start having that issue and few minutes later light pops up
scan gauge shows no abnormal sensors
both o2 sensors show normal readings as far as I can tell
fuel pressure is set at stock
new accel coil
oem rotor and cap
good ngk wires and new iridium plugs(or platinum I forgot)
running on stock obd2b ecu

when the power loss happens it goes lean over 16 afr and I feel it just fall on its face
but I cant figure out why its doing it

how can I test of the header is flexing and opening a gap or something when I take off because its very strange tahat it only does it in low gear first and second mostly I cant feel it in 3rd or up

 

have you ever replaced the fuel pump?
this might sound dumb, but do you recall what the fuel level in the tank was when it happened?

 

yea I got a different fuel pump the correct flow pump for r00 gsr

I had an unknown pump in it now its correct pressure correct pump and injectors

 

do you know if the fuel level was low each time the codes came back? reason I ask is because the sock may have fallen off, which sometimes causes it to suck air anytime you're below 1/4 tank

 

no I never removed the sock but fuel is full tank now when it throw code last time
I still feel like its electrical problem just don't know where else to look I
can the ecu be bad?
and how would I check that? obd2b

why only low gear tho I don't get that

 

P0420 IS NORMALLY A BAD CAT CONVERTER........

 

Yep P0420 is a bad cat and in some cases can cause you to get the other two codes.

Is the lean problem feel the same as you were experiencing a while back with the TPS?

Here is a quick guide to testing for the p0141 code. Not sure if you have done this.

http://troubleshootmyvehicle.com/gm/...a-P0141-page-1

 

the sensor is 6 months old denso oem replacement
it never throws both codes at the same time
its either p0420 or p0133
rear sensor is almost brand new too also denso

a bad sensor would throw a code constantly but I drive for a week or two without one
I had a bad ntk sensor in it and it popped the code right after I reset it every time

I also monitor voltages on scan gauge it looks normal even with the code on

I don't think the cat is bad as it only has 90000 miles on it came from a stock gsr that I did a swap in some time ago and when I checked it 3 weeks ago it had no abnormal colors and all clean through
'I have to check again it would be ground issue intermittent maybe wire melted or something

 

could this be a distributor issue?

I don't really want to swap the dizzy since the seal surface is damaged and if I move it I have to reseal it again

 

do you have access to a different ecu to swap out? my friends dads civic kept having o2 codes. we troubleshot the **** out of it one day and at out wits end we tossed in another ecu and it did the trick

 

fixed some wires at ecu( car had a vtak controller before I think)

crimped them properly and heatshrink car felt good for few hours

on the way back started lagging again and after about 10 minutes threw a p0420 code again


when I read online it says a lean condition can overheat the cat and make it less efficient giving a false reading to downstream o2 sensor as a bad cat.

which seems like whats been happening

still cant wrap my head around why it would lean out at low rpm in low gear and then not do it


only thing I can really think of is:
1 header flexes and leaks air before O2 sensor causing a lean reading ecu ads more fuel car chokes
2 post start is very rich or whatever reason when I take off the light and second gear theres way too much fuel and ecu overcompensates and cuts fuel giving a real lean condition and engine chokes.


I'm thinking cause and effect. effect is lean condition and cause would be either a real or a false lean condition right?

 

i tried obd1 gsr ecu and having same issue
but not as bad

obd2b has immobilizer kinda hard to find one and if i do i have to either break it off or buy an immobilizer board for it

the reason I'm suspecting electrical issue is:
car started with a b16a2 with stock b16a2 obd2b ecu
different cat and o2 sensors
same lean condition same O2 sensor codes thrown

changed back to original motor
different cat
new sensors
gsr ecu
different engine harness
same lean condition and same O2 codes

and its random i wish i had a datalogger to see what the deal is and what sensors are doing while all this crap is happening

 

agree with last statement. Pull datalog to see how O2 sensor working before it start chocking and trigger codes.

 

Most likely an intermittent wiring issue or ECU.

 

So basically same thing on both setups. With all different parts. What parts have not been swapped between the two motors? From the looks of your post the only thing I see is the wiring harness from the firewall to ecu?

 

yea pretty muh

 

It sounds like that may be the culprit, but to tell you the truth I have never really ever seen that side of the harness go bad. Unless it fried wires somehow.

 

I just installed an O2 sensor spacer to remedy a p0420 code on a Toyota. If you can watch the rear O2 sensor signal, it should not match the front sensor oscillation, they should generally flat line at around .6 volts.
Generally a p420 code shouldn't affect driveability.

 

went through the troubleshooting steps for o2 sensors
riddle me this

front o2 sensor
resistance at sensor heater 12.6ohm
no short to ground
plug reads no ground continuity at #3 terminal but has voltage with ignition on from #3 and #4 terminals


rear sensor
resistance 13.8ohm
no short to ground
no ground on either 3 or 4 terminals but 12 volt with ignition on between 3 and 4 terminals

all other tests show normal like jumping sensor wires and scanner reads proper voltage.
main relay
ground wire (yellow/green) reads 7.6 ohm continuity with ignition off

should the main relay ground read full ground or 7.6 ohm normal for it?


since the ecu motor engine harness and both o2 sensors have been replaced that leaves me with underdash harness main relay and underdash fuse box suspects

can the faulty circuit in fuse box cause this crap?

what does that circuit do anyway?(the circuit board behind the underdash fuse box)