I'm working on a friends car who mistakedly paid out 400 dollars to some idiot who replaced all sparks and ignition coils before identifying the code P0420 on her own at autozone and another place aswell. So trying to keep the bills down.
This is either the cat or the sensors. This problem came up 3 days after she had an exhaust clean at jiffy lube.
Car is a little slugish seems like its in the open loop fuel mode maybe, like i've read it should be, also has been driving for a couple months says she has hard time on freeway especially in 5th gear.
This is what i'm looking at.
There are two upstream and two downstream sensors on this car which i think the above connectors go to. It seems weirds as the downstreams don't go after the convertor in the exhaust but are at the bottom. THose have four wires and the upstreams have three they also cost less .
After testing the readings when the car is warm the first upstream has one wire that reads .29 and one that fluctuates between .1 to .9 or so. The second upstream is the same.
The two downstream have two wires that read .29 each and im not getting any fluctuating wires.
Don't know what this means for sure??? Seems like the downstreams have no fluctuating reading so it must be bad right?
Just troubled by the amount of sensors and the fact that there are up and downstream sensors and never found anything underneath the car by cat or after it does it look like im doing this right??? Does it seem like anything is wrong according to readings??? Thanks alot for the help.
I'm working on a friends car who mistakedly paid out 400 dollars to some idiot who replaced all sparks and ignition coils before identifying the code P0420 on her own at autozone and another place aswell. So trying to keep the bills down.
This is either the cat or the sensors. This problem came up 3 days after she had an exhaust clean at jiffy lube.
Car is a little slugish seems like its in the open loop fuel mode maybe, like i've read it should be, also has been driving for a couple months says she has hard time on freeway especially in 5th gear.
This is what i'm looking at.
There are two upstream and two downstream sensors on this car which i think the above connectors go to. It seems weirds as the downstreams don't go after the convertor in the exhaust but are at the bottom. THose have four wires and the upstreams have three they also cost less .
After testing the readings when the car is warm the first upstream has one wire that reads .29 and one that fluctuates between .1 to .9 or so. The second upstream is the same.
The two downstream have two wires that read .29 each and im not getting any fluctuating wires.
Don't know what this means for sure??? Seems like the downstreams have no fluctuating reading so it must be bad right?
Just troubled by the amount of sensors and the fact that there are up and downstream sensors and never found anything underneath the car by cat or after it does it look like im doing this right??? Does it seem like anything is wrong according to readings??? Thanks alot for the help.
those pics make me thankful i have a 2003 qg heh, only 2 sensors. probably getting a bad reading from one or more of the sensors. When i put my new headers on it happened to me until i chipped my 2nd o2 sensor.
The problem occured after an exhaust cleaning? That should be a big red flag. Can they take the blame? they most likely damaged something, what kind of service is that anyway?
Its not like a sentra is some big diesel truck. Damn, sorry about your car but its probably an 02 sensor downstream since the voltage doesnt change. You really need to check them with a scan tool and not just a volt meter, the actual readings may be incorrect.
This is alot of shit, but I just copied and pasted from alldata, so here you go
Without CONSULT-II
Start engine and warm it up to normal operating temperature.
Set voltmeter probes between ECM terminal 62 (HO2S1 bank 1) or 94 (HO2S1 bank 2) and engine ground.
Check the following with engine speed held at 2,000 rpm constant under no load.
The voltage fluctuates between 0 to 0.3 V and 0.6 to 1.0 V more than five times within 10 seconds . 1 time: 0 - 0.3 V -> 0.6 - 1.0 V -> 0 - 0.3 V
2 times: 0 - 0.3 V -> 0.6 - 1.0 V -> 0 - 0.3 V -> 0.6 - 1.0 V -> 0 - 0.3 V
The maximum voltage is over 0.6 V at least one time.
The minimum voltage is below 0.3 V at least one time.
The voltage never exceeds 1.0 V .
CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool J43897-18 or J-43897-12 and approved anti-seize lubricant.
HEATED OXYGEN SENSOR 1 HEATER (FRONT)
Check resistance between terminals 3 and 1.
Resistance: 2.3 - 4.3 Ohms at 25 °C (77 °F)
Check continuity between terminals 2 and 1, 3 and 2.
Continuity should not exist.
If NG, replace the heated oxygen sensor 1 (front).
CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
Before installing new heated oxygen sensor, clean exhaust system threads using Heated Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.
HEATED OXYGEN SENSOR 2 (REAR)
With CONSULT-II
Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes .
Stop vehicle with engine running.
Select "FUEL INJECTION" in "ACTIVE TEST" mode, and select "HO2S2 (B1)/(B2)" as the monitor item with CONSULT-II.
Check "HO2S2 (B1)/(B2)" at idle speed when adjusting "FUEL INJECTION" to ±5% . "HO2S2 (B1)/(B2)" should be above 0.48 V at least once when the "FUEL INJECTION" is +25%."HO2S2 (B1)/(B2)" should be below 0.43 V at least once when the "FUEL INJECTION" is -25%. CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
Before installing new heated oxygen sensor, clean exhaust system threads using Heated Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.
Without CONSULT-II
Start engine and drive vehicle at a speed of more than 70 km/h (43 MPH) for 2 consecutive minutes .
Stop vehicle with engine running.
Set voltmeter probes between ECM terminals 63 (HO2S2 bank 1) or 95 (HO2S2 bank 2) and engine ground.
Check the voltage when rewing up to 4,000 rpm under no load at least 10 times. (Depress and release accelerator pedal as soon as possible.) The voltage should be above 0.48 V at least once. If the voltage is above 0.48 V at step 4, step 5 is not necessary.
Check the voltage when rewing up to 6,000 rpm under no load. Or keep vehicle at idling for 10 minutes , then check the voltage. Or check the voltage when coasting from 80 km/h (50 MPH) in 3rd gear position (M/T), D position with "OD" OFF (A/T). The voltage should be below 0.43 V at least once. CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
Before installing new heated oxygen sensor, clean exhaust system threads using Heated Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.
HEATED OXYGEN SENSOR 2 HEATER (REAR)
Check the following.
Check resistance between terminals 2 and 3. Resistance: 2.3 - 4.3 ohm at 25 °C (77 °F)
Check continuity. If NG, replace the heated oxygen sensor 2 (rear). CAUTION:
Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
Before installing new heated oxygen sensor, clean exhaust system threads using Heated Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.
check out Doja's other post with these GREAT diagrams - they are VERY helpful. The is NO O2 sensor post catalyst on this car - i have the same model and year but it is auto. I am in the midst of determining which of my O2 sensors is throwing a code at me. I am getting p0420 bank 1 and am going to replace both front and rear o2 sensonrs associated with what the Haynes manual calls bank 1
Linear Mode
