P0156 CEL Code Help

Hello everyone,

Getting an intermittent P0156 and will throw a CEL. Passed smog like 2 weeks ago but at the time no light.

I hooked up a scanner and was getting voltage at B2S2 o2 sensor which is the area where p0156 is saying I’m getting the code at. Voltage is 0.1-0155 at idle. Is that normal? What could be causing this? Also getting voltage at the other sensors. Checked the wiring and they were good too.

 

You have zero truck info in your profile so I legitimately have no f’ing clue what you’re dealing with here and it makes it super tough to help you out.

Do you mind going into your profile: https://www.tundras.com/account/personal-details

Find the “Vehicle one line description” box. In it, put:

• Year
• Cab type (RC for regular, AC for access, DC for double)
• V8 or V6
• 2WD or 4WD
• Trim level (SR5, Limited, X-SP, etc)
• If it’s a manual, drop an MT on it

Example: 2001 DC V8/4WD SR5

I’m asking you to do this for a reason. Some trucks come with compatible rear sensors, and thus you can swap left-to-right to see if the code changes from B2S2 to B1S2, and if it does, you know the sensor is bad. I could check this part number info for you, but you are giving us no vehicle info in your profile and included no info in your post. Sensor config can vary by cab type, drivetrain type, engine type. Just update your profile, and we can give you truck-specific advice without having to ask every time, which gets exhausting.

About O2 sensors on these trucks…

• Always replace O2 in bank pairs (i.e. replace the upstream and downstream on same bank at same time)
• Only use Denso brand sensors for this specific part.
• Only use their “exact fit” sensor, DO NOT use the “universal fit”, you should NEVER need to cut wires to replace an O2 sensor (sensor wires are sensitive to tampering/splicing)
• DO NOT BUY these parts (or any other auto parts) on scAmazon or fleaBay, since knockoff parts are such huge problems on those sites.

 

Appreciate it. Just updated

 

Ok, I had to look up the SR5 and Limited vehicles because you didn’t put that trim info in your truck description. Looks like they both are identical on this one, so no big deal, just extra legwork for me. We don’t need to know your Tundra is a “Toyota”, that trim package info would’ve been more useful info in your one-liner. GD, I need some coffee.

If any of these part numbers I’m about to post show up as a link, it will probably take you to scAmazon. Never buy parts from there, or fleaBay. Risk of getting very convincing looking knockoffs is very real, and has happened to others.

Your downstream part numbers for V8/4WD in your year and cab type specifically are 234-4162, and upstream are 234-4169. These are the OEM part (made by Denso) and are a direct, plug and play part.

Because the downstream sensors are identical, if you want a $0 sanity check on this, assuming your sensors aren’t rusted to oblivion, you could swap the downstream sensors between bank 1 and bank 2 and clear codes. When you throw a code again, scan it. If it changes to P0136, you know that passenger downstream sensor (which is now on the driver side exhaust) was bad. I would buy one new upstream and one new downstream sensor, move the good downstream sensor back to its place on the driver’s side bank to return that pair back to normal, and replace both the passenger side sensors with the part numbers above.

Your local NAPA *may* carry those part numbers. DO NOT accept any part number except the ones I gave you, chain stores really love selling you on the “universal” sensors. Don’t use any other brand of sensor, part stores will try to convince you they’re all the same. If you want a guaranteed legit part, order online from Summit Racing or Rock Auto.

Oh, and if you don’t have one, the $10-20 O2 sensor wrenches truly are worth their weight in gold. Buy some penetrant to pre-loosen the sensor overnight. You may need it. They tend to be on tight.