Emissions Woes...

[CaptnInsaneO]

2002 Pathfinder, runs great & no CEL's but it keeps failing TX emissions test because the O2 sensors show as not ready on the shop's scanner.  Thoughts?

 

Thank You,

 

El Kapitan de loco

[Slartibartfast]

OBDII vehicles can take a while to decide they're happy with everything after having the codes cleared. I guess some codes take a while to re-set, so they wait until they're sure the sensor is good/system is working before showing as ready. (Otherwise you could just clear codes and go in before it coded again.) The question is what it's waiting for. Might just be a number of drive cycles, but I don't know that. The EC section of the service manual (free download from Nicoclub) might explain what it wants to see.

 

My cheap OBDII scanner shows whether the monitors have passed or whether it's still waiting on some. Probably worth picking up one of those so you know before you take it in.

[CaptnInsaneO]

On 7/14/2024 at 7:10 AM, Slartibartfast said:

OBDII vehicles can take a while to decide they're happy with everything after having the codes cleared. I guess some codes take a while to re-set, so they wait until they're sure the sensor is good/system is working before showing as ready. (Otherwise you could just clear codes and go in before it coded again.) The question is what it's waiting for. Might just be a number of drive cycles, but I don't know that. The EC section of the service manual (free download from Nicoclub) might explain what it wants to see.

 

My cheap OBDII scanner shows whether the monitors have passed or whether it's still waiting on some. Probably worth picking up one of those so you know before you take it in.

 

Thanks for the reply.  This is my 18 year old son's vehicle, so I am pretty sure he didn't think to plug a scan tool in before hand.  He claims there haven't been any codes to reset & he was told to drive it for at least 30 minutes before taking it to the inspection place.  I should be able to check the Pathfinder first hand later this week.

[CALPATHY]

Last time I cleared codes it took over 150 miles for everything to reset.

[CaptnInsaneO]

Update... Got my code scanner connected this weekend and the thing had a pending P0430 but no active codes being thrown or archived.  Checking the voltage readings for the O2 sensors, Bank 2 / Sensor 2 was "stuck" a 0.24 volts with no other activity.  Voltage output from the other O2 sensors was cycling up & down as it should.  We replaced the Bank 2 downstream, drove the vehicle for roughly 20 miles and then scanned it again.  The pending P0430 was gone and Bank 2 / Sensor 2's volts were cycling like the other 3 sensors.  Boy-O took it for another inspection attempt yesterday and it failed again for O2 not ready.   

 

Digging a little deeper into the scanner data, it shows that readiness for Heated Catalyst and Heated O2 are "not completed".  The pending code has not come back, so is it just a matter of driving more miles? (and continue risking getting several tickets) What could cause the O2's to never achieve readiness yet not throw a trouble code? 

Edited July 30, 2024 by CaptnInsaneO

[CaptnInsaneO]

Update Dos...  After doing an hour + of loops on a stretch of highway the Heated O2 sensor status finally updated to "Completed" in the scan tool. A few minutes later the Heated Catalyst updated to Completed too and then the computer promptly threw a P0430 code. Sigh... [/facepalm]

I ordered a set of Walker downstream cats last night & they should be delivered Saturday.  If they don't fix the issue anyone want to buy an offroad only '02 Pathfinder?!