02 Sensor Replacement Issue

Hey guys, I'm new here and looking for some advice. My 2005 Tacoma was running pretty smooth and then I had a check engine light come on. I took it to the local parts store who hooked it to the computer and found is had a bad 02 sensor in bank 1 slot 1. I researched and found that it was the upstream sensor, so I ordered one on Amazon. I replaced the sensor and the truck has been running fine however the check engine light would not go off. I decided to unhook my battery and let it set for about 5 minutes to clear the light. After I plugged it back up and started the engine the check engine light was off, but now my truck has a very low idle and eventually dies if I don't give it gas - and the check engine light is back on. Any advice on what I could do to fix this?

 

Run for codes again
Did sensors get banged around while out!
Check wiring
Can’t see having to do a idle reset after that

 

Thanks for the reply Greeves, the sensor didn't get banged around, and the wiring looks good. I will take it this evening and see what codes it pulls this time. This morning the truck didn't die on me, but it is still rough when idling.

Thanks!

 

A bad o2 sensor code rarely means a bad o2 sensor, cleaning the maf sensor usually is my first step just to check.
It could be a dozen different things.
Also I'd always recommend denso sensors for toyotas, I have a friend with a Camry who was always trying aftermarket ones, he switched ordering denso and it works much better. Pretty penny though.

 

Thanks Werewolf, I'll try cleaning the MAF sensor and see if that helps.

 

Clean your throttle body, it's probably dirty. Disconnecting the battery resets the learned idle position of the throttle body and would cause a low idle/stalling if it's dirty untill it is cleaned or it relearns itself.

 

Amazon is not a good idea to buy sensors. You need to buy original Toyota O2 sensor from Toyota Parts Store in your location. I believe that you have a good OBD II Scanner, if not - then you need one - ACTRON Elite Auto Scanner CP9185, $71.99.

 

Well, took it back to the auto parts store today. The code came back up as o2 sensor 1 bank 1. I did the idle reset and the truck is running much better now but the check engine light keeps coming on almost as soon as it's reset. I hate to spend $178 on an oem sensor if it's not even what is wrong with the truck. Not real sure what the MAF sensor is or where it's located, any help on that please?

 

Which code is it?

The reason the truck is idling low is due to carbon on the throttle body, the truck has to re-learn the idle and the carbon build up makes it take longer.

 

I took a pic of the computer

 

Have you checked the A/F Heater fuse and relay in the engine compartment fuse box?

 

I have not, but will do it first thing in the morning. Thanks!

 

https://www.tacomaworld.com/threads/how-to-throttle-body-cleaning-2005-v6.94203/

Worth a try. A couple cans of cleaner will be cheaper than a new OEM 02 sensor.

 

A Mass Air Flow sensor (MAF) is one of the key components of an electronic fuel injection system in your car. It is installed between the air filter and the intake manifold of the engine. The mass air flow sensor measures the amount of air entering the engine or the air flow. You need to buy MAF Sensor Cleaner from your local auto parts store, then take the sensor off and spray the wire until is clear from carbon deposits. Clean the trouble code and start the engine. If again you have the same code, then you need to spend $178 for a OEM sensor....you get what you pay for.

 

Here is a link to video about MAF sensor cleaning: https://www.youtube.com/watch?v=JIfWG3V1_Zg

 

Same code I had. Looked up correct O2 sensor here. https://densoautoparts.com/find-my-part.aspx#searchResults
Replaced it and CIL has been off ever since. Nov. 2020
I know I have an 04 3.4V6 but thought this might help
Good luck!

 

Well, take it to the dealer and get to the bottom of it fast. I know it costs $$$, but I want mine fixed yesterday!

 

You had P0031, HO2S - Heater control Circuit Low (Bank 1, sensor 1) and most likely solution is - replace O2 sensor. Yes, but not always. "most likely" and "Low" means that could be Catalytic Converter goes bad, bad gaskets, loose clamps, MAF sensor.

 

Best answer.

Tightening clamps is free. Crc maf sensor cleaner is cheap, unless you mess up and damage the sensor. Start there.

 

The A/F heater fuse and relay are common between both banks so I'd not suspect those as the cause, but you can measure the ohms of the bank 1 sensor 1 A/F sensor to verify it's in spec. If that check's out and your MAF is clean and reading good, you can also put a clamp on meter around the heater circuit B+ wire to measure the current, should be 0.8 amps DC minimum, do this with engine cold.