My 99 F150 just failed the TX emissions test. The check engine light came on last week, just in time for the test, and the computer showed errors: P0133 & P0171: O2 slow response (bank 1, sensor 1) & system too lean (bank 1)

Here's the question. Is the O2 sensor covered under the 8/80k emissions warranty? If not, how much does it cost to replace? Also, I've had various electrical probs already, including a faulty windshield wiper switch and odomerter ... could this readout be a bad OEDD unit?

Any help would be appreciated.
-sdb†

 

Good question.

I don't believe that an O2 sensor is covered. I think the Cats, the EGR system, Vapor canister, etc. are.

System lean code, huh?

I would replace the O2 sensors, as you are long overdue. Check all your vacuum lines, connections, and fittings REAL good. Then check your electrical connections- be as thorough as you can. I assume you've already given it a good tune-up (changed filters, checked plug wires, etc.)- if not, then that's another thing to investigate, it may not be the culprit, but it will help your truck run better and potentially lower your emissions. If that doesn't help, then I'm afraid the problem is deeper and a bit too technical (and could even be illegal) to try to fix at home. Fortunately, the deeper and technical things would be covered by the emissions system warranty.

A good rule of thumb regarding emissions failures:
High HC= unburnt fuel (usually ignition or fuel system problem)
High CO=hardware problem (valve seat, piston ring, etc.)
High NOx=Catalytic converter failure 95% of the time.

These aren't carved in stone, but are usually the main causes. Sometimes a problem like a vacuum leak can cause more than one item to go out (usually HC and CO).


Good luck!


---J

 

here in DFW everyone uses 'RXP' before taking new test. Use on 4 tanks in a row and it is supposed to cure all ills. Autozone or Oriellys have it in a little red bottle.

 

Just give your local dealer a call. It would surprise you what a code could show up at the inspection station as and yet the fix is something totaly different. Also once the fix has been taken care of don't run right back to the Inspection station, the codes will remain present for a number of run cycles before they clear them selfs. A faulty 02 sensor can be the result of a poorly sealed gas cap. This can also result in a run lean status via the computer. Trust me, I had the same situation on a 99 Mustang GT. Everything covered under the Emission Warrenty

 

You know, I changed to a locking gas cap just before the check engine light came on, I thought my neighbors might have been trying to get into my tank! Maybe it's not sealing correctly and producing no back pressure?

Ok all, thanks for the info. I'll do a quick tune-up, change the filters, etc, go back to the original gas cap, and run a couple of cycles to see if that does anything. Otherwise I'll take it to the local dealer and see if they can figure it out without taking too long.

-sdb†

 

gas cap will not give you this code. that p0133 will give you a lean code p0171. p0133 is a slow to respond. so when you start your engine. it take a long time for that thing to start switching. that could give a lean code. but you know that o2 is gone south due to the p0133. so replace it. and then clear pcm. take battery cable off for a minute. and then drive. if you still have lean code. its going to be vac lean or a miss. on the rh bank. but start with that o2. good luck

 

Ya'll never believe this.

I replaced one of the O2 sensors. Passenger-side, in front of the Cat. I hope that was the right one, seems to be. Got new fuel and air filters. Then I cleared the pcm and drove around, let it go two cycles.

Then, I went in for my free retest and the thing failed...not because of the O2, that was working fine, but the Evap & EGR system results weren't ready!

So now, I've got to go plop down another $40 for another test, and I got lectured by an 18 year old punk about trying to trick the system.

Anyone know anything about the waivers? What are they for?

-sdb†

 

Just to update; after changing that O2, passed emissions just fine, although it cost me $80 + parts! I appreciate all the input I got.

I'm interested in these chips ya'll are talking about. What sort of performace gains could a guy expect after installing one of these?

-sdb

 

when should i replace my O2 sensors? i have 49,000 on my 98 4.6. Also how often should the fuel filter be replaced? And PCV? when do i need to replace these things?