"P0100" "P0110" & "P0420" CODES

Hey guys and gals. My 20-year-old beauty is throwing some codes. A little history. About a month ago. It started throwing the "P0100" & "P0110" codes. So I cleaned the MAF sensor and it still threw the code. I bought a new MAF sensor and it is still throwing the code. I visually checked the prongs and harness and all seem to be fine. A couple of days ago, my check engine light came on, and it's now throwing the "P0420" code as well. I'm reading that this code can have something to do w the first 2 codes. Any thoughts? Suggestions? Thank you in advance. This group always pulls through.

 

Did you replace your air filter?

Also just get the URD O2 sensor simulator for the P0420.

 

No, I haven't replaced the air filter recent bud def within the time you usually replace them. Ill go get one today.

So is it my 02 sensors? i replaced the front one half a year ago. You think the back one is dying? Wouldnt it be better to replace the 02 sensors instead of the simulator? Just wondering.

 

B1S1 is an air/fuel sensor, has nothing to do with cat.
B1S2 is the cat nanny.

 

check for opens and shorts in the wires that go to/from the MAF. I can see a P0110 (air temp sensor) causing a P0420 as this is one of the inputs used to calculate fuel volume based on air temp.

Is the replacement MAF aftermarket or Toyota?

 

it was Toyota.

 

ok. It says one of the fixes could be one 02 sensor being lazy and not relating w the other 02 sensor. It is literally giving like 12 possible fixes so was just trying to narrow it down.

 

You have to differentiate information on sensor performance as to what sensor (s) are on the vehicle.
Your 01 3.4 has one a/f and one O2.
Older models had 2 O2 sensors that compared the amount of Oxygen before and after catalytic converter.

 

ok, in my model. Where is the a/f sensor? There is definitely a sensor before and after my cat. I know the one before is O2 as I've already changed it. I was thinking the one after my cat was an O2 as well. Is that wrong?

 

The sensor before cat (B1S1) on 2001 3.4 is an Air/Fuel sensor
DENSO 234-9001 auto transmission
DENSO 234-9003 manual transmission
https://densoautoparts.com/find-my-part.aspx
Top of pic is O2
Bottom is A/F

 

P0420 is due to the O2 sensor and its readings. Is it the sensor at the rear of the two. The front one is A/F.

 

Regarding your question about replacing rather than using a sim, that depends. Usually if your O2 sensor is malfunctioning, you would get a different code. You could try to clean the O2 sensor first, to see if the readings are perhaps off due to gunk in the sensor. But most likely on your 20 year old truck, the cats are dying, and therefore are not cleaning the air as well. There are aftermarket cats that can be had for <$500, but may not even get rid of the code, or you could spend $1500+ for new OEM cats. Or you could spend $120 on a simulator and run it if you don't have emissions testing or if you know you'll still pass a "sniffer" test. For my case, I'm almost certain I will still pass a sniffer test. However I would NOT pass with a CEL. Therefore the simulator was the obvious, and far less expensive, solution.

 

ok, so I guess the one I replaced last year must have been the a/f. It is the one in front of the cat. So the back one is the O2? Should I buy a new one to see if that's the problem or do you think cleaning it would be suffice? I live in CA so we have emissions. Thank for your help.

 

You would have to ask someone from CA. I would try to clean it first. But if that doesn't work then I'd expect to either replace the cats or use a sim. Someone who has a sim and lives in CA may be able to help more with respect to passing or not

 

Replacing your O2 sensor will not improve cat performance. P0420 = catalytic converter below performance threshold.
Bad sensors have their own code #s.
Solve the P0100 and P0110 and the P0420 may disappear.
You may have an exhaust leak before the catalytic converter which will throw a P0420. An exhaust shop can heat test the cats and check for leaks cheaply.

 

I just cleaned my air filter ( which was pretty dirty), so waiting for that to dry. If its still throwing code, what would you suggest next? stripping the tape off the wire and tracing it back to see any rips?

 

@eon_blue

 

Normally I'd say it's the cats, but with those two sensor codes on top it might be related to them. Id try and fix those two codes first and hope the P0420 follows

 

Do you have a washable filter?

 

yes, its drying right now