About 6 months ago my car threw a code and tripped the light. It was P0174. I checked everything recommended to check and found nothing wrong so I replaced the O2 sensor that was recommended. I reset the ECU with my OBDII scanner and the light turned off. Since then... hundreds and hundreds and hundreds of miles of trouble free driving with not even a hiccup and no check engine light! Great right? NOPE. My car has failed emissions 3 times because 3 systems are still reading not ready with my OBDII scanner. These 3 systems are CAT, O2 Sensor and EVAP. Because of this... my car fails emissions.
The repair shop said they can start throwing parts at it to see if it helps to clear it but because the car is running perfectly with no issues whatsoever and no thrown codes to check there isn't alot they can do. They said to keep driving it. Its been about 300-400 miles so far.
Just ranting I guess.
It sucks to own a car that I have loved for 10 years, a car that saved my life when I had a massive heart attack, that all of my kids used in HS and then college, my wife used for work and I have been driving back and forth to work, a car that runs perfectly and is STILL a joy to drive only to come to the conclusion that I am going to have to sell it as is to somebody for next to nothing because it won't pass emissions!

 

Its a problem that has plagued my 4th gen every two years when it comes time for emissions. Its a very common misconception that you need to drive x miles to get your monitors to set. When in reality you need to perform the drive cycle.
Get your money back from the shop if they seriously think that throwing parts at the car will get the monitors to set.

This is the one that has worked well for me. If certain monitors wont set, repeat the pattern specified for that monitor.

 

Wow, I downloaded the drive pattern procedure. So incredibly complicated.

 

Lol jgcable, your not selling your maxima dont worry, what year is your 4th gen.

 

Its a 1997. My family has put 110,000 miles on it over the last 10 years.

 

And as a side note... its as fast as the the 1st day we got it. What a great car.

 

Picture your driving habits and how you use your car.

You might not be doing a certain kind of driving which the ecu might want to monitor. Which explains the not ready.

So if you would do things with your car which you normally dont, your system might change to the ready status.

For example, if you are gentle with the gas pedal, the ecu never sees how the car responds to high throttle demands.

look at that chart again. Notice which parts are tested under each condition.

Basicly, you are not using your car under all the conditions the ecu is looking for.
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I understand all that but its really hard to follow the patterns prescribed. The systems not ready on my car are O2 Sensor, CAT and EVAP.

The chart for my car is Pattern #14. I can't figure out what to do. For instance CAT. I assume that would be #5 CATALYST. If I am reading this correctly....car must be cold. I drive 50-60 mph with the OD off keeping the engine speed at 3000 rpms and do not slow down for more than 3 consecutive seconds. I am pretty sure that if my car is at 3000 rpms with the overdrive off I am going to be going considerably faster than 60 mph.
I also don't understand the second trip thing.

 

I don't follow the chart if I'm in your situation.

I intentially drive the car under all situations I can think of. Old lady like, then aggressivly, hot, cold, short , long.


I don't know what variety of conditions your car experiences during any given week.

it seems to take about a week between a reset and a system ready.

 

I've always wondered about this. What happens if you have the car repaired by a shop? They don't take it out and drive through the pattern, do they? Do they just tell you it won't pass smog inspection for a while?

 

I already tried this once. After my car failed emissions because these 3 systems weren't ready I drove the car 300 miles over several weeks. Every driving condition you can think of. Fast, slow, rotting in traffic, on the highway, around town etc.... The systems would not reset to ready.

 

I asked this exact question at the local repair shop. They don't go out and drive around following specific patterns to get the systems to show ready. I went to 3 different local reputable repair shops and they all gave the same answer. If they repair a car and it needs to go through emissions after they clear a code they tell the owner to drive around for between 50 and 100 miles and all systems should clear.

 

Possible ecu short or some wire shortage. The evap lines solenoids and harness all connected.

 

I read about that driving pattern to have the car in ready status .I recommend buying a scanner so you know when your car goes into ready status, if you don’t have one already.

I was having the same issue not being ready. Was told to just drive the car but that didn’t help. Then found that procedure above on line, somewhere else. if you follow that you should be good.

Havent had a chance to drive my car yet but im going follow that procedure more or less. Get the car on the highway early morning so you can do the acceleration to 50 mph then back down to 0 like the graph shows.