clarky14

It's all clean. So this p0420 I didn't see when I originally scanned this car days ago. I'm thinking the af sensor by the firewall might be the culprit.

artbuc

Why? Based on what? If you have a bad A/F sensor it will throw a code.

clarky14

I had those codes the other day. They probably didn't pop up yet because those two monitors havnt reset yet. But based on p0171 and p0420 what do you think it is?

artbuc

Have you reset and driven after cleaning MAF sensor? If yes, did you still get 0171 and 0420? Hopefully you do not have a bad cat converter but that is a possibility. If your downstream O2 sensor is original, it is most likely not working and I would check it. Did you ever confirm if either or both of your A/F sensors are original? Is your code scanner capable of measuring A/F voltage output? What are your short and long term fuel trims? I hate throwing parts at a problem but if your two A/F sensors and downstream O2 sensor are original, I would replace them first (with Denso only) and go from there. You still could have a vacuum leak somewhere.

clarky14

I just went for a drive again after resetting the codes and this time the 420 code came first then minutes later the 171 code

clarky14

The sensor by the radiator looks newer than the one by the firewall. The one by the radiators blue wire appears a lot bluer than the firewall one

clarky14

I'm not able to measure that stuff with my scanner. My scanner does say that these codes are pending and the cel isn't on. The catalyst and ev monitors aren't ready either.

artbuc

You need to have someone with the right equipment and knowledge diagnose your car. You can roll the dice and replace all 3 sensors starting with the downstream O2 sensor. If that does not work, replace both A/F sensors. If you still throw codes, assuming your MAF is working ok and you do not have a vacuum leak or a freak issue such as a loose ground or faulty ECU, you most likely have a bad cat converter. Making decisions based on how blue the wire is will not get you anywhere.

clarky14

Unfortunately they don't have that luxury right now with fiananicial stuff going on right now. Thats why I am trying to help.

artbuc

Good-luck. Sorry I could not help you.

artbuc

Any progress?

clarky14

I've been sick all week. Trying to find a good day to install sensor.

clarky14

I'm back. Took the car for a test drive. When I picked up the car it had the check engine light on and the trac off light was on. The codes were p0171 twice and p0420. I cleaned the throttle body and MAF sensor with the battery disconnected. I took it for a drive and at about 10 miles the p0171 code popped up as pending. I kept driving another few miles and then the p0420 code popped up as pending. I will also say that driving above 40mph if you put the pedal to the floor the car is sluggish. It feels like overdrive isn't engaging. But anyways that's where I'm at right now.

artbuc

Lots of info available on this code combo, eg

http://www.toyotanation.com/forum/26...171-p0420.html

Based on your symptoms, I would focus on fuel delivery. What are your long and short term trims? What is your fuel pressure at the rail? Could be a failing fuel pump or plugged fuel filter. Also could be a vacuum or exhaust leak, faulty/dirty MAF sensor, faulty upstream and/or downstream oxygen sensors. Finally it could be a faulty/plugged cat converter.

Here is a good article re cat converters. Is your car burning a lot of oil?

http://www.aa1car.com/library/converter.htm