Problem: P0156 error code indicating a malfunction with the oxygen sensor circuit on "Bank 2, Sensor 2
Solutions taken: Replaced both catalytic converters and all 4 O2 sensors (Denso brand)
Still getting error code.
Next proposed solution: Check whatever fuse that's associated with O2 sensors
Problem: None of labeled fuses makes it apparent.
Thank you!
Solutions taken: Replaced both catalytic converters and all 4 O2 sensors (Denso brand)
Why did you replace catalytic converters when that code indicates a problem with the O2 sensor circuitry? Or is there more going on than what was mentioned? Did any of those replaced parts test as bad before replacement?
Next proposed solution: Check whatever fuse that's associated with O2 sensors
The "solution" we generally recommend is diagnosis rather than loading up the parts cannon, unless a particular part is obviously bad. There are a few different possible causes for that code:
https://www.carparts.com/blog/p0156-code-o2-sensor-circuit-malfunction-bank-2-sensor-2/
https://www.obd-codes.com/p0156
Have you checked for wiring problems?
Chances are that any fuse for the O2 sensors would be for the heaters only, not for the signal. There are other codes specifically for O2 sensor heater problems. P0156 refers to the O2 sensor signal.
Problem: None of labeled fuses makes it apparent.
Check your owner's manual or a repair manual for fuse details.
Thank you for such an informative reply. Couple of quick points:
- I replaced both catalytic converters AND 4 O2 sensors as a preventative maintenance so-to-speak. Just buying it with 177,800 miles, I figured why not. Especially with the error code making it likely I had at least one bad O2 sensor.
- I did not test the above. I figured Denso was considered a solid brand of O2 sensor...and very unlikely it was "bad". Am I wrong in that assumption, though?
- I have not checked for wiring problems other than visually being under the Sequoia putting in new Denso O2 sensors (disconnecting old...connecting new). The connectors and wires associated all "looked" perfect. Did not see any wear and tear.
- Awesome clarification of yours pointing out P0156 refers to the "signal" part of O2 sensor....not heater.
Could an unsealed part of catalytic converter (such as where the pipes connect) cause this? I've seen some suggest those parts should be sealed with exhaust putty.
If you have access to a scan tool, check the signal voltage for the Bank 2,2 oxygen sensor with the engine at normal operating temperature. Is it stuck low currently? If so, increase RPM for a few seconds and see if it affects the reading. If it begins working with increased RPM, check for holes in the exhaust near the o2 sensor that may cause a false lean. If the exhaust pipe is intact, the sensor is sluggish, replace it.
If the Bank 2,2 o2 sensor voltage reading remains low with increased RPM, unplug it and then observe the reading. It should have increased to about 0.5 volts or thereabouts. If it did, check for water intrusion or other connector problems. If none are found, replace the shorted o2 sensor. If the voltage reading is still stuck low after unplugging the sensor, then suspect a wiring problem. Using a voltmeter, with the o2 sensor unplugged, check for voltage on the signal circuit at the o2 sensor connector(PCM side). It can vary with model, but should be about 0.5 volts and not above 1 volt. If the voltage reading is too high, repair short to voltage on signal circuit. If the signal voltage checks out, suspect the PCM.
(excerpt from: https://www.obd-codes.com/p0156)
@imperator I have this Klein multimeter...will it do the job?
O2 sensor voltage is best measured with a scope or diagnostic scanner. Your multi-meter can provide rudimentary info like no signal at all.
I replaced both catalytic converters AND 4 O2 sensors as a preventative maintenance so-to-speak. Just buying it with 177,800 miles, I figured why not.
It's not really necessary. Unless poisoned by engine problems like oil burning or excessively rich mixture, damaged by rust-through, or suffering from other physical damage catalytic converters don't wear out. Mine has 28 years and over 370,000 miles on it with no problems.
Given the age of the vehicles you probably have the old-school narrow-band O2 sensors that can be tested with a scan tool via live data, or even with a voltmeter.
I figured Denso was considered a solid brand of O2 sensor...and very unlikely it was "bad". Am I wrong in that assumption, though?
A shocking number of new parts these days are defective out of the box. Depending where you bought the parts there is also a chance they may be counterfeit. (Ebay and Amazon are the primary offenders.)
I have not checked for wiring problems other than visually being under the Sequoia putting in new Denso O2 sensors (disconnecting old...connecting new). The connectors and wires associated all "looked" perfect. Did not see any wear and tear.
In addition to a visual check you would need to test continuity and resistance from the O2 sensor to the ECU to verify wiring condition.
Could an unsealed part of catalytic converter (such as where the pipes connect) cause this?
Only if there were a noticeable exhaust leak as pointed out in the description of P0156.
@chucktobias Ughhh.....I bought my Denso on ebay. The seller had sold 98399 items with a 97.6% positive rating. Thought I was making a sound purchase. Maybe they are good...but it sounds like what you are saying is to be SURE...test them.
They might be be real, but it can be hard to tell the difference visually. But it would not be surprising if they turned out to be counterfeit. Don't take our word for it, if you do an internet search for "ebay counterfeit car parts" you'll find a lot of chatter about the problem. Amazon has similar problems.
https://www.youtube.com/watch?v=LJ-ma1w8r6Q
@chucktobias Is the sure fire way of checking to make sure - - by using a multimeter to check? One of the videos you linked above was excellent....it showed a bad sensor being around 7-10 ohms. Then he checked a new one and it was around 16. Unsure if this works in identifying a bad knockoff or not.
I really don't know if you can check them that way. In operation a narrow-band O2 sensor should be constantly varying its output between just over zero to just under one volt. As @imperator said a scope or diagnostic scanner is best used to graph the output but you can get a rough idea using a voltmeter. An analog meter with a low voltage scale actually works best since it's easier to see the voltage swings.