O2 Sensor CEL Code and Resonator Delete (1 Viewer)

[wsudu]

Hi everyone, I have a P0158 code that popped up after a CEL went off. The exhaust is definitely smelly and running rich as well. I used tech stream and it said the voltage is high (1.25v or more) on this particular (bank 2 sensor 2) 02 sensor. I am installing a 4x4 Labs rear bumper and cut off the resonator. Do you think that has something to do with it? I did drive around without it for about three weeks without any issues. I do have tech stream and before I start spending $50-80 on one or more sensors, is there something I could do to check for inside TS or check that it is the sensor, perhaps test it? I read reports sometimes of people saying it's a spark plug or something else that isn't shown causing the O2 sensor failure when the while time it was fine. Thanks

 

[morganism]

Is the truck garaged, and you left it out for the first cold snap of the year?

In some of the Toys, there is a firmware bug in the computer, that throws a code when the block coolant sensor, and the outside air temp is different by 45o or more.

You need to try the Readiness Monitor reset first prob. I run the moms Corolla without any O2s now, and get the same mileage around town.

Toyota/Lexus OBD-II Drive Cycles | Car OBD Diagnostics, ECU Chip Tuning & Auto Repair Support

" Readiness Monitor Drive Pattern" that you need to reset?

Toyota Service Bulletin EG003-02

You need to clear the computer, and do it in a place you can drive over 35 mph for at least 10 min.

disconnect Neg batt cable, turn key to ON a couple times to drain comp batt.

 

[abuck99]

Cutting the resonator off will not impact your fueling. Check your fuel pressure regulator, and your fuel pulsation damper for proper function.

 

[Spike555]

Just replace both of the rear O2's and be done with it.
Buy cheap ones, the rears do nothing other than monitor the cats for efficiency. They have zero to do with engine fueling or performance.
You can get a pair of them for $50 if you shop around.
The front's spend money on not the rears.

 

[wsudu]

Thanks guys, did not think that the resonator had anything to do with it but you never know. I went to the dealer and with my clubhouse discount it was $165, so I called another dealer with my discount it was $135. I found a Denso for $50 bucks on Amazon so I'm going to do that, it is getting here today.

 

[wsudu]

So I put the new Denso O2 sensor in and it seems to have not fixed the problem, which is what I was afraid of. I noticed that after I got it up to temperature and I reved it up to WOT, bank 1 02 voltage drops down to about .15 V but no matter what, the new sensor I replaced on bank 2 stays constant about .85 V, close to maximum. Fuel trims on that bank are also significantly higher in long-term. Here is a screenshot from tech stream, maybe this will help. What else should I be looking at? I was thinking about swapping bank one and bank two sensors just to try.

 

[Spike555]

I'd swap sensors form side ot side and see what happens.
But, everytime you reset the check engine light the ecu needs to run a complete drive cycle before it will stop using the default fuel mapping.

 

[wsudu]

Thanks Spike, I just tried that and got the same result. Now Im a bit lost. Someone up above said to check the pressure regulator and fuel pulsation damper. I have no idea how to do that so off I go to search. I have heard everything from a vacuum leak, to clogged cats, to a loose spark plug so who knows.

I'd swap sensors form side ot side and see what happens.
But, everytime you reset the check engine light the ecu needs to run a complete drive cycle before it will stop using the default fuel mapping.

 

[Spike555]

I have no idea about the fuel damper.
Faulty fuel pressure regulator could cause over fueling.
Loose spark plugs cause incomplete combustion.
Vacuum leaks cause lean conditions.
Clogged cat's cause exhaust restriction, loss of power and over heate cats.

 

[wsudu]

Well, after reading this thread here: P0156 and P0158 error codes it was the A/F sensor just above it. Even though it was throwing no codes itself and the voltages and ratios looked good, it was lying to me and causing the O2 code I was getting initially. I swapped the A/F sensors and have identical numbers on bank 1 now, so I know it is wrong. Hopefully this can help someone with this code or a P0138 code for the bank 1 O2 sensor.

 

[schnee]

Sorry to revive this thread, but just wanted to relay my experience in case it can help anyone.

A week ago, CEL went on with P0138 (High voltage on Bank 1 sensor 2). This is the same as P0139 which is for bank 2. I cleared the codes by disconnecting the battery and then took a 60mi highway trip. My MPGs were in the 12s (down from 16-17) and after about 30mi, the CEL came on again and it was the same P0138 code. Since the code didn't indicate an error with O2 sensor 2 on bank 1, I found this thread and figured I would try diagnosing the A/F sensor.

I took off the A/F sensors on each bank and cleaned them using CRC Intake Valve cleaner, following this video:

The CEL is off and the engine appears to be running normally. I'm not sure this will fix it for long, so I may need to buy a couple of A/F sensors in the future. By the way, Amazon has the Denso part for a lot less than the dealer: Amazon product ASIN B0018JUJ9O

 

[wsudu]

Sorry to revive this thread, but just wanted to relay my experience in case it can help anyone.

A week ago, CEL went on with P0138 (High voltage on Bank 1 sensor 2). This is the same as P0139 which is for bank 2. I cleared the codes by disconnecting the battery and then took a 60mi highway trip. My MPGs were in the 12s (down from 16-17) and after about 30mi, the CEL came on again and it was the same P0138 code. Since the code didn't indicate an error with O2 sensor 2 on bank 1, I found this thread and figured I would try diagnosing the A/F sensor.

I took off the A/F sensors on each bank and cleaned them using CRC Intake Valve cleaner, following this video:

The CEL is off and the engine appears to be running normally. I'm not sure this will fix it for long, so I may need to buy a couple of A/F sensors in the future. By the way, Amazon has the Denso part for a lot less than the dealer: Amazon product ASIN B0018JUJ9O

Well, if it makes you feel any better since this thread posted, it's been about 2 1/2 years and I've had 10 to 15,000 miles on the truck with these four new sensors, no problems at all.

 

[schnee]

Thanks @wsudu, it turns out the cleaning didn't do much good. I had the CEL turn on 30mi later, so I bought a pair of the Denso A/F sensors and installed them. It's been running great ever since.