Denso 02 sensor, code won’t clear?

So we just bought an 09 Tacoma TRD sport. 168k Drive of the lot and engine light comes on. Go right back and it throws a code for bank 2 sensor2 02. They put a new NGK sensor in. We drive 90 minutes to get home, light is off. 2 hours later, light is back on. Doesn’t appear to be any exhaust leaks. I replaced the air filter. Truck seems to be running strong. I checked the temp going into the catalytic converter’s, seems close going in and out. Was told I needed an OEM sensor (Denso) so I replaced that yesterday, cleared the code and 2 hours later light on again. A/F fuse is good. Truck was inspected (NYS) a day before we got it and passed. Going to look for bad wires today. Any thoughts? Thanks in advance!

 

What code is it setting?

 

P0157

 

Need to look at data on a scan tool and see what the sensor is reading at operating temp.

 

The impedance is reading 21247.10
Not fluctuating at all.
Voltage .49

 

Impedance on B1S2 is about 600

 

Does the voltage fluctuate between 0 and 1v with changing engine conditions or is it just stuck at 0.49?

 

Yes fluctuates

 

This looks eerily similar to an issue I had with a Highlander V6 a couple weeks ago at the shop, it had an open sensor ground in the PCM.
I think I recorded data from a test drive, I'll have to look. If I did I'll post it up.

Assuming the correct sensor (Driver's Side downstream) was replaced we need to check wiring integrity to the sensor.

Pin 4 (Brown) is the sensor ground, it should light a 150 mA test light connected to battery positive

If you take a test light connected to battery positive and touch it to the signal wire (Pin 3 (Blue)) key on while watching scan data B2S2 voltage should go to at least 1v.

 

I didn't record the impedance when it was broken but here's what it looked like when it was broken (B1S2 was the problem one).


And after I fixed it.

 

Thank you, I’ll check this out.
We were thinking it may be something with the ground or wiring but haven’t checked that yet. I’m going to Check what you sent me next. I appreciate it. Driving me nuts.

 

I had this code from an exhaust leak that repairing the leak fixed it. It was small. Sensors were known good already replaced.

 

Did I mention it also threw a P0161 code when we checked it. Don’t know if that really changes all that we’ve been checking.

 

you say “they” put a sensor in. I would be suspicious.
When I did my sensors there was no “they”. I put them in. I cleaned the threads and put hot bolt paste. I torqued them. I inspected and verified absence of exhaust leaks.

this can be done by inspecting the exhaust. By clogging the tip with wet rags to increase pressure. To cold start it. By spraying soapy water, feeling with your hand, and listening for noise.

and no “they” to not catch something, lie about something, or not do diag from not being paid to do diag. Makes it way easier. No game of telephone.

if it’s in NYS, the exhaust is probably rusted.

ECM failure is extremely rare. Not saying it’s not possible. I’ve just never seen it.

wiring issues are also possible. But if it made it this far from the factory the wiring might be fine.
Rodent chew does happen. Depends on where the vehicle is stored and what the wire sheathing is made of (some brands use sheathing more tasty to rodents)
That can also be checked.
typically a rodent will bite straight through, causing an open circuit fault (not low voltage) and possibly pop a fuse pointing to the circuit.

also not common. Last wiring issue I dealt with on a car was because somebody hackjob’d a recall to flag time without doing the work, on a German car. Had to find it and fix it.

yeah you can do a pin draw test. Inspect and clean the connector. Wiring checks. But it also may be an exhaust leak. Maybe a bad cat.
Issues with the drivetrain causing lean condition such as failing fuel delivery system is also not good.

but inspecting the exhaust is a good start, mandatory minimum requirement if you haven’t done it already, and kinda free to do. Thats just my take on it.

 

That's a heater circuit code, if the heater isn't working then the sensor won't operate properly.

Pin 2 (Blue/White) is the heater power, it should have power with the key on.

Pin 1 (Blue) is heater control (ground side) this one is a bit more tricky to test because i don't believe there is a bi-directional control for the downstream heaters and the PCM won't turn them on until the exhaust comes up to temp.

I put a test light across pins 1 and 2 and watch the scanner to see if my light lights up when the PCM commands the heater on, if it does I know my heater circuit is good. If it doesn't then I know I have a problem.

 

Thanks guys, I will check.

 

I blew a head gasket on my gen 1 - 3RZ (4cyl) ,It leaked coolant so bad it hydrolocked and skidded to a stop
I changed out the motor with a low mileage 3rz from a rollover
a few hundred miles later I got this code ( rear O2 sensor )
front O2 read the same as rear O2
I took off the cat to see what it looked like and it wasn't melted so I tried to clean it with brake cleaner spray, still no workie
So I wrapped the rear O2 sensor with stainless wire around where the exhaust gas enters to confirm
After wrapping, the rear reading was lower than front reading and code never came back.
I think the coolant ruined the original Cat
I eventually found a good OEM cat from a wreck

 

So the light went off by itself for about a day. Came back on for 2 days and now went out again. We still have to check the wiring. ‍♂️