O2 Sensors

I just hit the road on a camping/kayaking trip and my check engine light was on. First time I have ever seen it in 8 years and 50,000 miles. I had oil pressure and no overheating so I was not worried about it, but i stopped at AutoZone and had the kid come out and plug in the diagnostic tool. He took it back in and plugged it in to his computer and it said i have a bad O2 Sensor. Sounds reasonable. I went ahead and towed my camper the 40 miles to the site.
My Haynes (or Clymer?) book says I have 3 O2 Sensors if I understand it correctly. It's got the V8.
1. Can I test each one and replace the bad one or do I replace them all?
2. Do I need an

$6 O2 socket , 7/8" (22mm) with 3/8" Drive, Universal Fit for Vehicle Oxygen Sensor Removal

O2 socket?
3. How difficult is it to remove and replace the O2 Sensors on a '03 Access Cab Tundra?

 

What was the specific code?

 

That depends.

Are you 2WD or 4WD? It matters. Substantially. 4WD has two different part numbers for your year, for the downstream sensors.

Is it the upstream or downstream? AuzoZone prints out a sheet of paper with a code on it. What's the code? Downstream is wildly easier.

Use www.densoautoparts to find the correct part# for your truck. Don't buy it on scAmazon or fleaBay. Don't buy aftermarket on this one, either Toyota or Denso brand.

 

Sounds like I need to go to another parts store and get it scanned again. So I have more information.
The person I dealt with did not offer a print out. Just said there’s more than one and you gotta “dig around in there” to figure out which one it is. I has happy to confirm it was nothing serious and just wanted to get on the road.
Its 4WD.
Thanks

 

There are 4 O2 sensors - 2 on each side. Bank. 1 is the driver side and Bank 2 is the passenger side. 2WD and different than 4WD. Make sure you only use Denso. Please post the code or codes - P and 4 digits.

 

Assuming you're V8 - if not, please include that info too! - your V8 part numbers for Denso (factory) brand replacements for V8/4WD are below. The P#### code you're given will indicate which needs replacement. RIGHT is passenger, LEFT is driver. Downstream is after the catalytic converter (practically under the front seats), upstream is between the cat and engine, usually right up near where the exhaust manifold flange meets the cat flange. Upstream are the same part number for your year. Again. DO NOT buy these parts on scAmazon or fleaBay. You'll get the cheapest prices on authentic, genuine Denso parts from RockAuto, or Summit Racing (whose price will be higher, but they should price match to RockAuto!). Counterfeit risk is very high from those. Local stores don't usually sell Denso, and if they do, they're 50-100% more in price.

I personally prefer to replace the upstream and downstream sensor at the same time. Like, if passenger downstream is bad, replace passenger downstream and upstream. They work together in pairs to tell the ECU if your catalytic converter is working correctly, and if the upstream is bad, the downstream may not be far behind it. But just having an old, tired sensor working with a fresh sensor, you may start throwing a cat efficiency code. If you're strapped for cash, maybe wait, and see if you trigger a P0420 or P0430 code (those are cat efficiency codes).

Get an O2 sensor socket. It has a slot in it to slide over the sensor wire, then attach to a ratchet and pop off. Tekton is a great brand, byt the Lexmily someone posted will probably work too.

If you live in the rust belt, you may want to hit it with penetrant like Kroil or PB Blaster once or twice over a couple days while hot to quench it and hopefully loosen it up.

​

 

This is excellent information and advice. Thank you. I’m on it!

 

P0051
HO2S heater control circuit low (bank 2 sensor 1)

 

That code means the O2 sensor heater is not operating as expected. Once the vehicle is warmed up, the O2 sensor is likely functioning just fine. The heater speeds up the time it takes to get to temp so the truck can start using the sensors for AF metering. Not dire to replace them in the middle of your trip, but good to replace them soon to keep optimum efficiency And prevent running rich which eventually ruins catalytic converters. Replace in pairs with Denso as described above.

 

I bought Denso part # 234-4162 and 234-4169
The right front is bad so I’ll replace the front and rear on the right (passenger) side.
62= $109.99
69= $89.99

 

I ran into a mess. Hopefully the pictures show it. I could not grip the connector and pinch and pull so I just cut the wires. The blue wire was cut off and just hanging out there. It looks like someone jumped one of the other wires and bypassed the connector. Maybe there was damage to the connector? How should I put this back together?
Also the sensor turned right out without much resistance. It doesn’t look like the crush washer is crushed.

 

Those are typically shielded wires I think, not something you want to cut.

 

Also, this is the downstream sensor. Any idea what kind of fasteners these are and how to remove them?

 

It’s just a nut. The sensor is bolted to a diamond shaped piece of steel with a hole in either side. It slides over the stud and the nuts hold it on. One is heavily corroded. Chip away the rust.

OR hammer a socket on. Spin off.

 

I’m up to my 7th penetrant spraying after getting home from work. By the time I get around to changing them hopefully they’ll unscrew by hand. lol

 

Dremel and very sharp cold chisel. Or you could give it a shot with a nut/bolt extractor like Rocket Socket.

Basically a nut over a stud. The stud can be replaced although some people have broken them off.

 

The upstream sensor was a challenge but the downstream one was easy. Those two bolts turned with a six-point wrench.
How do I clear the check engine light?

 

OBD2 reader.

 

After (or while) changing the sensor, you'll want to pull the negative battery cable, for at least 10 minutes.