2001 Maxima GLE: Trying to pass smog (star certified) in California. Smog tech is saying the "OBD-II Not ready" for O2 sensor. No CEL is on. No codes. Car has low mileage (143K total) and has been driven just under 2,000 miles since November 2021 (I work from home).

Tech said to drive it a bit to get the OBD-II system to a ready state. So, that day I put 100+ miles on the car doing random highway (60-70mph) and local cruising while running errands. Still not going to ready state. I have read through several posts on the forum, and one thing that came up was that the OBD-II may never recognize the system as "ready" no matter how much I drive.

Any recommendations on how to proceed? I hate to just start replacing parts, but it sounds like I may need to replace an O2 sensor (or 2 or 3 or 4 of them) to get the system in ready mode. I will spend time checking all wiring/connections as well, but I was assuming that if the wires were not connected or loose that it would have CEL'd already.

Any cheap(er) OBD-II scanners I could buy that would at least tell me it is ready for testing without having to go back to the tech randomly?

Car runs fine other than this smog issue.

 

When they get old, they get lazy. Replace with quality sensor (bosch or denso).
Don't replace all of em, just that specific one.

It's easier to leave the state minus the Uhaul shortage of epic proportions

 

I'm glad I live in Florida where we don't have any vehicle inspections to worry about.

 

Any cheap(er) OBD-II scanners I could buy that would at least tell me it is ready for testing without having to go back to the tech randomly?

 

You're not using a bluetooth (or wifi for iTrash) adapter and car gauge pro?
Slacking, son.

Also, NDS2 is very niiiiice.

 

I have an old ELM327 (bluetooth only) and an old Android phone with the Torque app on it. That app seems to only read fault codes and reset the codes. Perhaps it is capable to do more, but I have never messed with it much.

 

An android app called Car Scanner works well for reading and clearing codes. and can tell you what is ready or not. i was using it for my o2 issue.

 

I tried to connect my old ELM327 to bluetooth on an iPhone, but found out the iPhone doesn't support this older bluetooth version. After lots of Googling, I found an free app:

https://www.obdautodoctor.com/

This one I can load on a MacBook that I have and connect to the ELM327 (again, older model maybe 5+ years old). According to their features on the pricing page, the free version can give me the readiness monitor information I need.

https://www.obdautodoctor.com/pricing/

I'll try this out later tonight when it is not 100+ degrees outside.

 

So I got around to hooking up OBDAutoDoctor app (pro version $37.99) via my ELM327. It states "Not Ready" on the O2 sensor. Of course, which one(s) is/are the problem?

So I took two captures of data:

1. Just idling in the driveway for a short time, here are the averages:

B1S1 - Output Voltage: 0.12
B1S1 - Shot Term Fuel Trim Percentage: -7.8
B1S2 - Output Voltage: 0.3
B1S2 - Short Term Fuel Trim Percentage: No Data (not monitored?)
B2S1 - Output Voltage: 0.47
B2S1 - Short Term Fuel Trim Percentage: -10.9
B2S2 - Output Voltage: 0.3
B2S2 - Short Term Fuel Trim Percentage: No Data (not monitored?)

2. Took the car for a quick spin around the block, here are the averages:

B1S1 - Output Voltage: 0.51
B1S1 - Shot Term Fuel Trim Percentage: -9.4
B1S2 - Output Voltage: 0.3
B1S2 - Short Term Fuel Trim Percentage: No Data (not monitored?)
B2S1 - Output Voltage: 0.65
B2S1 - Short Term Fuel Trim Percentage: -10.9
B2S2 - Output Voltage: 0.3
B2S2 - Short Term Fuel Trim Percentage: No Data (not monitored?)

Looking at the data, I see that O2 Sensors in B1S2 and B2S2 both have a constant output voltage of 0.3V. This seems odd that they have no change? The other two O2 Sensors had voltages with varying range. B1S1 was 0.03V to 0.91V and B2S1 was 0.03V to 0.92V.

Any thoughts on this data? My initial guess is that B1S2 and B2S2 are both bad? I'm going to pull the connectors tomorrow when the engine is cold and check them. I believe there is also a continuity test I could run on them?

Many thanks in advance.

 

I ordered all four(4) O2 sensors from RockAuto today. I'll replace the two lazy ones (B1S2 and B2S2) and see if that gets me to status ready for smog.

 

Finally got the O2 sensors (all 4) replaced. The O2 Sensors went Ready state as I drove up to the smog station for testing about 5 miles away. Passed emissions. Hooray!!

On a side note, this also seemed to have corrected a "stuttering" problem I had with the car only at startup when the engine is cold. It had a strange "backfire" (technically more of a "front fire" or "popping noise" up front) that has now gone away as well.

 

Glad to hear that you resolved the issue and that it passed smog! Where in CA are you located?