Hi Guys,
I need a bit of help. Here is the story.

Last week, I went to get a smog check and failed. The car is running perfectly, no CEL, although there was one "incomplete monitor" - for the front pre-CAT. I was under the impression that one incomplete monitor is OK, but I was wrong; they just changed the law, at least here in California. No "incomplete" monitorss are allowed, with the possible exception of EVAP. At any rate, the guy at the smog station offered to run a special test to force a pass/fail. The result was a CEL with P0430 code (front pre-cat efficiency poor).

After some deliberation I decided to replace the front (pre)CAT, with OEM/Nissan part. I am the original owner so I figured I'll spend $1000 and the car will be fine for a while, or at least for another 2 years. My mechanic did the replacement for me last Friday. Since then, I have been trying to complete my monitors. The problem persists - the CAT monitor is still incomplete, although all the other monitors completed fairly quickly.

I have now driven over 350 miles and the problem persists. Tried various "drive cycles" I collected from my mechanic, from the internet, and from the FSM (in particular, I ran the test/DTC confirmation procedure on p. EC-433 of the 2000 FSM).

I am now wondering about several issues suggested in the FSM:

• Leaks. I don't think I have an intake leak, and I'll be checking for any exhaust leak tomorrow.
• Measuring the "switching frequency ratio" to evaluate the overall function of the pre-CAT seems like a good idea. Unfortunately, measuring voltages and frequencies on ECU terminals is a bit tricky for me .... . How do you do that - do you just place probes into the connector by your right foot??
• Should the above test fail, the list of suspects grows: front O2 sensor, PCV valve, MAF, injectors, etc.

Any advice or suggestions?

My mechanic suggested replacing the battery, but I am not sure that will fix the problem although the battery is 5 years old (but still holds voltage/power well). Should I rather see the dealer - will Consult II find the correct answer?

 

I could be wrong but sounds like an o2 issue....not a bad pre-cat.

 

All you can do at this point is work through the drive cycles to complete the monitor. Doing anything else is just throwing more money at the problem and won't necessarily resolve anything.

Did you disconnect both battery terminals and reconnect when the precat was replaced? You can try doing this to help clear the ECU and start over. In my experience, the monitor completes quickly only when you have the P0420 or P0430 error code come back up. When you don't, then it takes longer to complete the cycle and become "ready" for whatever reason...

 

Guys, thanks for your help; I do appreciate it!

Here is an update: I took the car to one of the better dealers in the area and asked them to diagnose. The answer was: the precat I just replaced (B2) is OK, but the B1 precat is failing (that's the Cat in the Y-pipe). They showed me the wave forms.

With my sunken costs, I had no choice but replace. After some negotiation, they did it for $1,300 including taxes and all. They also drove the car and made all monitors "complete", so I can finally go and get my smog check tomorrow. So far, my cost for this new California law is: ($59.95 + $90) + $992 (B2 cat)+ $1300 (B1 cat) = about $2,500 total!

I am not happy. If I knew all this, I would have bought a new Honda Accord instead ....

On the other hand: There was another customer there waiting for his car: '97 GLE, 400,000 miles, with original Catalysts. He bought the car for $5000 (salvaged title), and drove it from 100k to 400k miles, unlike me, mostly highway miles. The car looked great.

Life is not fair.

 

That sucks...you could have fixed this with O2 spacers for about $20 on both banks. The only downside on this is the possibility of not passing visual inspection since O2 spacers are not California smog compliant.

 

They did visual inspection. Whether they would see/report a well-installed spacer is a good question.

 

Stories like this always remind me of why I live in Florida.

 

Wow glad they dont do inspections here in south carolina. Thats alot of money to pay!

 

If you plan on holding onto the car a good while longer and run into these code issues again try the spacers first and see what happens. You can always claim ignorance and your mechanic put those in. You get a slap on the wrist with a non-compliance and need to fix it. Definitely worth the risk in that case with $20 versus $2000 dollars...

Make sure you stay on top of your spark plugs, ignition coils, and primary O2 sensors. Running rich with any excess fuel kills pre-cats.

 

Well, that's what the emission guy at the dealership also said: that my pre-cats shouldn't fail, that they often last 200+k miles. I change my plugs every 30k miles, and my coils were replaced 10 yrs ago at 50k miles (replaced with gray dot coils, are good). The only thing I have not replaced yet are my primary O2 sensors - both are still original. Also, my driving - the last 6 years or so - is mostly short trips, 5-15 miles per trip. What do you suggest: should I replace my primary sensors as a precaution? If so, what brand; Denso or Siemens?

Edit: Also, the car runs very well, can't complain of anything. However, the pre-cat problem (p0430) came up in winter/snow driving in 2011, then it went away, and this year came in the form of incomplete cat monitor. It's the new California law that caused my trouble (the car may be perfectly clean but it doesn't matter).

 

LOL at lasting 200K+ a majority of org members have had the P0420 and/or P0430 code before 200K miles.

You can replace the primary O2 sensors, but if you have an OBD reader you can read the voltage as they run and see if they are within the FSM parameters. If they are...leave them.

 

Same problem with passing smog here in California. After doing some research, I found a Smog Check OBD Reference manual that lists cars with known OBD issues. Of course, the 2000/2001 Maxima makes the list for inability to set catalyst monitor. It won't set no matter how long you drive it or put it through Drive Cycles. It is a problem with the onboard system. Spoke to a technician at the CA Bureau of Automotive Repair and he said that only the dealer has the scan tool that can show the catalyst code. So Nissan has screwed us again such that instead of paying $20 at a local smog shop we now need to take it to the dealer and pay $$$. I had the P0430 code about a year ago but nothing since and over 5000 miles driven since the code was cleared. OBD reader doesn't show any codes or pending codes. At least CA will give me $1000 to retire the car which is better than spending over $2300 to pass smog. It has 205K miles on it, 3 oil leaks, and needs work on steering/suspension.