O2 Sensor Reader throwing codes

Hello all, I searched the forum and did not see a post about this, but apologies if it has been discussed before.

I got my 2000 SR5 4.7l at 119k miles and the check engine light was on. When replacing the timing belt, water pump, LBJs, etc… the mechanic said the engine light was showing an issue with the O2 sensors. He replaced them all and the light was still on, but this time only for bank 1 sensor 1. He replaced it one more time to ensure it wasn’t a faulty part and the light persevered. He said it was probably whatever sensor reads the status of the O2 sensor that was messed up as bank 1 sensor 1 had been replaced twice.

This was 2 years and about 35k miles ago. I’d like to get rid of the pesky light but not sure where to start to diagnose what’s actually wrong. The codes my OBD shows now are P0125 (Insufficient coolant temp for closed loop fuel control), P0130 (O2 sensor circuit bank 1 sensor 1), P0133 (Bank 1 sensor 1 slow response), and now Bank 2 sensor 1 also.

Another thread mentioned it could be a cracked exhaust manifold? Anyone got any ideas or ran into something similar? Would it be worth it to try replacing the O2 sensor again?

 

The manifold was also my first thought. Is it making a ticking noise?

Also check the wiring of the O2 sensors, even past where they connect to the main harness

 

Thank you for your response. There is a ticking noise upon starting that usually speeds up whenever I accelerate. I believe this could be a crack in the manifold from what I’ve read here? I am not as knowledgeable in engines as most members here, but how would the manifold cause this O2 issue?

 

Definitely a leaking manifold. Could be a crack or a blown gasket.
You can either replace the manifolds or buy some headers. JBA makes some new shorty headers that are basically a direct swap and I think they're cheaper than buying the OEM manifolds. Either option will come with new gaskets too.

The leaking manifolds are where I would start and see if that solves the O2 issues. Exhaust leaks can trigger O2 related check engine lights .

 

Ticking sounds like classic manifold crack that happens.

These trucks are really sensitive on sensors. Folks have had problems with every brand of O2 sensor except Denso brand, and a few have had luck with Bosch. People have had issues if someone is a dumbass and cuts the harneses to use universal sensors.

You or your mechanic really needs to take a minute to validate the grounds for the O2 sensor circuit also. Inspect the harness for damage, and throw a meter on the grounds to verify they're good. Verify all the grounds on the engine.

Silly side question, but is the A/C working properly?

 

I will definitely look into the wiring. AC works surprisingly well, but the blower motor does need a knock to get going often times. I’ll usually tap it with a small baseball bat.

 

Starting to get this project planned. This is the kit I’m looking at. https://www.autozone.com/exhaust/exhaust-header/p/jba-exhaust-header-2010s/414591_0_0

would I need anything else for the job? Got a quote for $1400 just for labor if I supply the part from one local shop which seems high but I’m not sure.

 

Should be all you need. Definitely high. I paid that much to get headers installed on two of these trucks.

 

Thank you for the reply. Thats what I was thinking. Working with a private mechanic now that I have worked with previously.