SES Codes P0420 and P1404

'99 FB V6 134500mi, my SES light came on again with the below codes:

DTC P0420 Catalyst System Low Efficiency
DTC P1404 Exhaust Gas Recirculation (EGR) Closed Position Performance

I've replaced the EGR valve last week, recently I had installed a new high-flow cat along with a new 02 sensor in the cat and Flowmaster exhaust. Could the above codes be related to the new cat? If so, would it just be a matter of getting some adjustments to the computer to fix this or do I need to look somewhere else?

Thanks
Chris

Hey Chirs,

I've been on hiatus and out of the autmotive loop for a while so don't quote me on this just yet until someone backs me up or rebuts me, but, if I remember correctly, with the high flow cat setup, the post cat o2 sensor(s) need some tweaking. I know on the V8's there's enve o2 'deletes' available.

I'm certain to guess the SES light came on right after the cat was installed? If so, yes, the codes are a direct result of the post cat o2's reading the higher flow which is outside of the OBDII's system tolerance level.

Actually I was getting the P1404 code prior to that and intermittently the 0420. I assumed the cat was going bad since it was over 10yrs old. After I replaced the EGR valve I still seemed to intermittently see the 1404 code. Today I borrowed the code reader from work which seems to be a lot better than the one from AdvanceAuto. The only code that showed up this time was the 0420, prior to clearing it I decided to check the O2 Sensors operation. It shows I have 3 sensors. It showed that #1 and 3 were operating correctly, when I went to check 2 it shows that "sensor 2 is unavailable". To me as a not so smart guy it sounds like sensor 2 is bad. If so, where is it located? I've been trying to find time to take it to the same performance shop my son takes his but things at work always seem prevent it. Guess I'll see if I can get him to take it down there for me on his day off see if all it needs is some 'tweaking' of the computer. I know when he had his headers installed and new cat (his cat didn't have an 02 Sensor port) they fixed him right up.

Thanks for the reply.

Chris

Capot, I think I have the same issues. I don't know if its a low threshold something, well its that what I don't know if its a p0420 and I too got a high flow cat and since I put on the check engine light is on. Please update on whether you did get the o2 tweaked or not.

Sure will, I'm just puzzled about this 'sensor 2 is unavailable' reading.

Capot, I think I have the same issues. I don't know if its a low threshold something, well its that what I don't know if its a p0420 and I too got a high flow cat and since I put on the check engine light is on. Please update on whether you did get the o2 tweaked or not.
Problem solved. Took it to the same performance my son takes his to and they did a 'street tune' which changes quite a few parameters in the computer so I'm told. I could try and get a list of what they did and post it.

I'm glad you fixed it. Ok let apologize for using your thread here, yeah ever since you said something about tweakin the o2 sensor, a tuner tune shop came to mind like you did, but here is my ? To you, should I go straight to the shop and get my car tuned like yours or should I buy the o2 sensors and then take it to get tuned. And again sorry for using you thread.

I'm glad you fixed it. Ok let apologize for using your thread here, yeah ever since you said something about tweakin the o2 sensor, a tuner tune shop came to mind like you did, but here is my ? To you, should I go straight to the shop and get my car tuned like yours or should I buy the o2 sensors and then take it to get tuned. And again sorry for using you thread.

I only replaced one O2 sensor and that was the one in the new cat. Some of the things that were done:

The EGR valve was taken out of play
The shift points were changed, shifts with a bit more 'umph' now
The top end cutout was set to 255mph
The fan settings were changed to come on sooner

I'm sure there are more changes made and I may not have remembered all the above correctly. As far as exhaust I'm running a highflow 3"in/out cat with 3" pipe back to an 80 series flowmaster. The reason I changed the O2 sensor in the cat was that I wasn't sure they'd be able to get it out of the old one when it was removed though it did cost abut $70.00.

How much did you pay for the tune?
Because I think that's what I'm gonna have to do, and I too have changed the cat. O2 sensor. And my fb has 198,xxx and its a 2000 coupe 5 spd.

How much did you pay for the tune?
Because I think that's what I'm gonna have to do, and I too have changed the cat. O2 sensor. And my fb has 198,xxx and its a 2000 coupe 5 spd.

1999 and just turned over 135k. The street tune cost 340.00.

Geeeeeeez, that's what I thought.
Ok, what if I buy the hypertech programmer instead, would be the same with the advantage I can go back to stock options?
and actually I don't know how much will this tuner shop in mesa az will charge me for it.

Geeeeeeez, that's what I thought.
Ok, what if I buy the hypertech programmer instead, would be the same with the advantage I can go back to stock options?
and actually I don't know how much will this tuner shop in mesa az will charge me for it.

Personally I can't see any advantage in buying the programmer, in fact I just did a search and they run, from what I can see, almost $400.00. That's quite a lot to spend if you're only going to use it once or twice. Why not just call the shop, tell them what you want done, and get a price.

We'll, good news. I don't if I told you this but it was a p0440, evap sys. I had already replaced the gas cap and nothing. Then I had given up on it. Later on I came across your thread, and it got me thinking again. Went to this shop in mesa az, turn out its not the same shop so, no dyno tunes. I read online the p0440 has to do with the purge solenoid and EUREKA!!!!! It turned to be that. Now that I think about it, I did smell gas every time I turned the car off but it never dawned on me , I took as the car being old and too many miles. Anyway, thanks for you input on this and I'm stoked that my car no longer has a ses light anymore..... hope I don't jinx myself by saying this.

Ok, if anymore problems arise on your car that stomp you, hopefully I can help as you did with mine. Good luck.