# 2000 Altima P0446 code 255,000+ miles



## BillHoo (Nov 13, 2006)

I've been getting a P0446 code and I need to resolve in order to pas Virginia state emissions test.

So far, I have replaced:
- Gas Cap - and I ensure it is turned 3 times before start up.
- Vapor Canister Vent solenoid
- Charcoal Canister
- EGR Solenoid Valve

After I install the parts, I clear the code by either disconnecting the battery or using an OBDII reader. The code keeps coming up within 4 miles of driving.

The car has since May - just take it for a spin or two around the block every couple weeks.

I have a Vapor canister purge valve on its way from Rock auto this week. Will see how that goes.

Anyone have ideas?


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## smj999smj (Jan 1, 2006)

There are a number of possibilities that can cause that code to trigger. I would download a copy of the factory service manual and follow the diagnostic steps for P0446 to properly isolate the cause of the code.


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## BillHoo (Nov 13, 2006)

Putting in the new Purge valve did not work. I reset the code and then drove it around for about 75 miles and it came back on.

I brought it to a an emissions specialist who spent two weeks testing everything related to emissions and he even requested all the old parts to test those out too.

Got the car back last night. He said the ECM is bad and it would cost about $1000 to repair. I told him I didn't want to spend that and he gave it back without charge. He recommended to junk it.

The recent ECM diagnosis brings to mind some strange problems that have popped up in the last 5 years.

Since 2007, the dashboard will just fade away at random. All LCD displays disappear, the speedometer shuts off, no rpm indicators, etc. then they come back on after a few miles. Dealer shop could not find any problems.

2008 was driving on freeway when the SES and airbag lights began to flash and the car suddenly ran rough and lost power. Had it towed to dealer and they said they did something to the ECM. I think they charged around $500 back then. Car ran great.

2011 during a really hot summer, none of the keys would work in starting up the car. I thought it might be the heat or something, so I let the car sit and a week later, it started up like no problem, with one key, but all the other keys still don't work - and they were the original keys I got with the car when I bought it new!

2013 another hot summer. I was 10 miles from my house and the car started to drive rough and the SES light came on. I was barely able to get it home only by flooring the gas. It died in my driveway and I couldn't start the car. Left it overnight and next morning it started up like no problem and the SES light was gone.

2013 two months later. I was driving the car and happened to be a block away from my mechanic when the car stalled at a light. After a few cranks, it started up, but only if I floored the gas. I limped into his shop and he couldn't get it to start. He did a bunch of diagnostics and said it looked like the #2 cylinder wasn't firing. He figured the distributor was bad and ordered a refurb to be delivered. He did not the next morning car started just fine, but replaced it anyway.

2014 hot, late summer. Car does the same thing a mile from home. Engine rough, but no SES light. Let it sit for four hours, then started up and drove home.

2015 Cool March weather, it ran rough while I was starting on a long trip - SES light went on and was flashing. I know to turn around drive it back home and barely made it.

May 2015 SES light has been on and showing the P0446 since the. Car has been driving fine.

In my recent test drives, the dash still fades out randomly.

Does the ECM need to be re-flashed maybe?

I might just bring it to one of the nearby Nissan dealers for one final opinion. I used to bring it to a great dealer shop nearby and a terrific relationship with the manager there. But they closed up about 7 years ago. Then I found another great dealer shop 5 years ago and they closed up also. The two near me have gotten bad reviews, but I don't want to drive too far with the expired sticker.


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## BillHoo (Nov 13, 2006)

So, I took it to the dealer this week.

They did their diagnostic and found everything works fine, no need for a new ECM.

They thought it was a break in the wire between the ECM and components related to the code. They said they could do it for $500 with tax. Total came out to $540.

They took it out for a 10 mile test drive and then brought it in to get an emissions test. Tested good! They threw in the Emissions test for free. I can register the car now. 

Minutes later, they found another fault for the thermostat that caused the check engine light to come on for an EGR fault that they traced to faulty thermostat. 

Estimate to replace the Thermostat and flush coolant is $720. I figure I can do that myself. 

They also recommended to rebuild the brake calipers for the front estimate $900. I'll do that myself too.


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## OhmsLaw (Mar 29, 2016)

It could be the regulator failed and so all the electronics was exposed to 17v for months, and so it has all been damaged but won't fail outright. 
Or, maybe it was in a flood.

Aside from that, there are methods for making the repair/replace decision. I have one written down somewhere. 
The subject comes under "Quantitative Methods in Management" or something like that.
It takes a spreadsheet to do the calc.

I would have given up on this car. What would have to happen for you to give up on this car? To some extent, driving it is risky.


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