Okay... so i bought just recently bought a 2001 QX4. Love the car (as i'm sure all of you do) but i've had the check engine light on since the day after i bought it.

First code p0171. Took it in to infiniti... they said replace the MAF. Did it. Replaced it with an after market OE MAF. reset the codes.

Light came back on. Code is now p0420. I took it back to infiniti, and asked him why he couldn't diagnose this problem code along with the MAF. Code wasn't there he said. He said because i installed an after market MAF, that could be the problem (BS i think). Dealar reset the codes himself... but light came back on with same codes

So what can i do to fix this p0420. I'd hate to have to bring it back into infiniti and pay another $150 for diagnosis. All i want is my new car to be w/o a service engine light.

Thanks much everyone for the help. This forum (and all of u) is AWESOME!!!

I'm in absolutely same situationI had my MAF replaced (now twice because of the silicone filter) because of the combination of P0171 and P0320. Now this is passed and i get P0420 and the same old P0320 coming back every day. I do have a small Exhaust leak though which I'm planning to take care of next week.This car is so damn sensitive.Any advices ???

stop smokin weed in ur car and u wont get a code 420

okay... heres what i ended up doing.

I took the car to my mechanic, and he did a bunch of scans on the car... figure out it was a faulty cat convertor. And because my car has under 80 thousand miles on it... it was still under warranty (federal warranty).

I went back into the dealer and told them to replace it. They call me back 20 mins after i dropp the thing off, and tell me its an o2 sensor, and it'll cost me 500 bucks. When i asked to speak to the mechanic who diagnosed this, the told me they'd call me back.

5 hours later... the same guy calls me and tells me they just needed to update the ECM... and that was covered under warranty too. It did end up working and i haven't had the check engine light come on since.

Summary.... p0320 could be exhaust. p0420 could be cat. but make sure they update your ECM to the latest software at the dealership. Because if it is not updated .... the old software can cause miscues in the cat/o2 system, and not regulate the engine correctly, therefore turning the service engine light on.

Let me know how it goes, and GL

FouRTwOZerO wrote:stop smokin weed in ur car and u wont get a code 420

FouRTwOZerO wrote:stop smokin weed in ur car and u wont get a code 420

HaHaHa

cant' stop laughingsuch an appropriate comment - and so usefully tooyou must be a comedian

FouRTwOZerO wrote:stop smokin weed in ur car and u wont get a code 420

You know he's been waiting forever for that code to come up

Billy

Gurthy wrote:okay... heres what i ended up doing.

I took the car to my mechanic, and he did a bunch of scans on the car... figure out it was a faulty cat convertor. And because my car has under 80 thousand miles on it... it was still under warranty (federal warranty).

I went back into the dealer and told them to replace it. They call me back 20 mins after i dropp the thing off, and tell me its an o2 sensor, and it'll cost me 500 bucks. When i asked to speak to the mechanic who diagnosed this, the told me they'd call me back.

5 hours later... the same guy calls me and tells me they just needed to update the ECM... and that was covered under warranty too. It did end up working and i haven't had the check engine light come on since.

Summary.... p0320 could be exhaust. p0420 could be cat. but make sure they update your ECM to the latest software at the dealership. Because if it is not updated .... the old software can cause miscues in the cat/o2 system, and not regulate the engine correctly, therefore turning the service engine light on.

Let me know how it goes, and GL

I have almost an identical story as you, only they told me that updating the ECM was NOT covered under warranty (~$200).

The only thing is, I read that the ECM update just widens the "acceptable" range for your catalytic converter. Your (and my) converter was out of compliance for your old computer program, so they update the program to make it fall within compliance. Then your converter slowly gets worse until it's out of compliance with the new program. Of course, they hope this happens after your warranty runs out so they get you for $200 on the ECM update and they get you paying for the catalytic converter replacement.

I'm generally skeptical, but it sounds like it's a business move instead of some novel solution...