O2 sensor/P0156 code (2 Viewers)

[landarcht]

Replaced my bank 2 CAT yesterday, got the rig tuned up the week before with all fluids replaced, fuel injection cleaned, new spark plugs and thought everything is refreshed, the O2 error code came up after about 20 miles of driving. Bank 2 sensor 2 (downstream?), cleared them, it came up after about another 20-25 miles, cleared the codes again, it came up again about another 15 miles. Same code always. I'm not an expert on reading all the OBDII categories, but just comparing with Bank 1 and sensor 1 and Bank 2 sensor 1, it appears that the Bank 2 sensor 2 is reading extremely low, while driving it is almost 0.000 to 0.056, wen idling it may go up to 0.3'ish, but as soon as I step on the gas, it will go back to 0.000 again. Just trying to pinpoint if in fact it is the O2 sensor I should replace. Since the code has been consistent. Or could it be something else? Car drives fine so I can't tell. Is there other readings on the OBDII that I should be pa

 

[jerryb]

that other guy that said swap sensors is probably correct.
if you don't know the age your 4 you should replace them all just because they're cheap. Unless you have a vvti, fronts are double.

if in fact you were actually seeing .03 back to zero V then replace both bank 2 sensors. I don't remember what year you have.

 

[landarcht]

2005

 

[landarcht]

As far as I know, it's not a VVTI. Will check for leaks to make sure it's not anything else but I will replace them as needed.

 

[Trunk Monkey]

I think you have this question going in 3 threads now? It would be great to keep the info in one place both for those trying to help you as well as others searching for the same issue. If you ran a bad o2 sensor for years as you've said, you probably fouled the cat and subsequently the downstream sensor. You've replaced the cat, now you have a bad sensor code, just replace that sensor. Or better, as suggested, start fresh with all 4 new so the ECU is mapping correctly.

 

[landarcht]

Will do. Just need some help getting the correct O2 sensor part number. I was on Rock Auto and saw two Denso sets of numbers for up and down stream, just wanted to be sure I'm looking at the correct ones for my 2005. The website doesn't indicate which one is Bank 1 and Bank 2.
2344138/2349051 both are upstream (2349051 is about doubled in price)
2344260/2344154 both are downstream

 

[NE Snowman]

Found this for VVTI vs non VVTI.

If the 10th digit of your Vin# is a 6, it will have VVTI. If it's a 5, it will be non-vvti. Cheers

 

[landarcht]

Confirmed non-VVTI.
Did more research on the Denso part numbers and came up with below: If someone can confirm would be appreciated.

234-4138 upstream threaded mount
234-9051 upstream w/ 8.5" A/F ratio sensor
234-4260 downstream threaded mount
234-4154 downstream flange mount

 

[jsloden]

I was having the EXACT same problem as you about a year and a half ago. Mine was intermittent. When the cel was on the values would be as you described. When it was off they would be normal. All of this started after I replaced the exhaust manifold. First thing I did was replaced the sensor. This seemed to work for a few months. Then it was intermittent again. I then replaced the gas cap. That turned it off for a few more months. Then it came back again. Then I used two cans of bg 44k and I started getting gas at a different station. This seems to have fixed the issue. I also cleaned the maf and the throttle body and everything else. I am determined not to spend an ungodly amount of money on a cat. If I have to I'll just put in the factory straight pipes and cheat the sensors. Beauty of living in a state without inspections.

 

[landarcht]

I use Mobile station since that's the closest to my house. Did you see any other code? It's only been the P0156 for me after CAT was replaced and they told me it was plugged pretty bad, it was an aftermarket one. Bank 1 is still factory OEM, no issues. MAF also clean and replaced gas cap. Also dumped in a can of 44K few months ago, a can of Techron yesterday. I just order four sensors but now I'm wondering if I should return them.

 

[jsloden]

Were you getting the code before you replaced the cat. P0156 is just the code for the o2 sensor, not the cat

 

[NE Snowman]

He replaced the cat because it was fouled, the sensor should be replaced too because it’s also most likely toast. Replace that sensor… I’d replace at least both upstream and downstream at the same time. If it was my truck I’d do all 4 like @Trunk Monkey said so your ECU has fresh mappings before and after cat, it’s how the whole system works.

 

[landarcht]

I had code P0430 (Bank 2 CAT) for some time, P0156 code came up when downstream sensor was unplugged while I was trying to find a reputable muffler shop. But the Bank 2 sensors are less than a year code. CAD code no longer comes up, now just consistent P0156.
I should receive all four sensors tomorrow.
2x 234-4138
2x 234-4153
back checked with Toyota, all Densos.

 

[Trunk Monkey]

Any follow up after replacing all 4 sensors?

 

[landarcht]

Replaced two for bank 2 along with the cat about two weeks prior. Also did fuel injection flush with oil change. Runs like new again! No issues so far. Hope I don't jinx it.

 

[Freddy1333]

Ongoing P0156 code a week or 2 after a new sensor fitted. History - a couple of months ago the head gaskets were replaced and heads planed due to combustion gases leaking into the cooling system - all good now. Traces of coolant were also apparent in cyl 6 when doing a leak down test (which showed which cyl was leaking). The code can be cleared but will return within a week or so. I suspect that the Cat has been contaminated with cooked coolant, causing the CEL repeats.

Question: is there an O2 sensor eliminator/plug/adapter/thingy available that can be plugged into the harness in place of the actual sensor to stop CEL repeats? TIA.


Anyone familiar with this: Toyota Land Cruiser O2 Sensor Eliminator MAGNUM EZ CEL FIX Oxygen Sensor Simulator - https://www.magnumtuning.com/en/detail/ez-cel-fix-oxygen-sensor-simulator/toyota/land-cruiser

 

[NE Snowman]

I know t4r guys had a guy who used to make a spacer with a small piece of cat in it. Within the last year he stopped selling them though. Spark plug defouler is the other option?

Then you have the simulators for people who deleted cats and such.