O2 Sensor question

Shredicus

Shredicus

Dedicated LVC Member
Joined
Dec 24, 2011
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Location
Palm Springs, CA
So I recently bought a bluetooth OBDII reader and hooked it up to the app "Torque". It popped up a few errors with the o2 sensors. Here's the report:

Test report:
------------------
MID:$01 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 1 Sensor 1
Max: 7.99527V Min: 0V
Test result value: 0.44994V
PASS
----
MID:$01 TID:$80
- O2 Bank 1 Sensor 1
Max: 7.99527V Min: 0.49996V
Test result value: 0.8213V
PASS
----
MID:$01 TID:$81
- O2 Bank 1 Sensor 1
Max: 3A Min: 0.465A
Test result value: 1.068A
PASS
----
MID:$02 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 1 Sensor 2
Max: 7.99527V Min: 0V
Test result value: 0.44994V
PASS
----
MID:$02 TID:$81
- O2 Bank 1 Sensor 2
Max: 3A Min: 0.27A
Test result value: 0.529A
PASS
----
MID:$03 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 1 Sensor 3
Max: 7.99527V Min: 0V
Test result value: 0.44994V
PASS
----
MID:$03 TID:$81
- O2 Bank 1 Sensor 3
Max: 3A Min: 0.22A
Test result value: 0A
FAIL
----
MID:$05 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 2 Sensor 1
Max: 7.99527V Min: 0V
Test result value: 0.44994V
PASS
----
MID:$05 TID:$80
- O2 Bank 2 Sensor 1
Max: 7.99527V Min: 0.49996V
Test result value: 0.83753V
PASS
----
MID:$05 TID:$81
- O2 Bank 2 Sensor 1
Max: 3A Min: 0.465A
Test result value: 1.039A
PASS
----
MID:$06 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 2 Sensor 2
Max: 7.99527V Min: 0V
Test result value: 0.44994V
PASS
----
MID:$06 TID:$81
- O2 Bank 2 Sensor 2
Max: 3A Min: 0.27A
Test result value: 0.521A
PASS
----
MID:$07 TID:$01
Rich to Lean sensor threshold voltage(constant) - O2 Bank 2 Sensor 3
Max: 7.99527V Min: 0V
Test result value: 0.44994V
PASS
----
MID:$07 TID:$81
- O2 Bank 2 Sensor 3
Max: 3A Min: 0.22A
Test result value: 0A
FAIL
----
MID:$21 TID:$80
- Catalyst Monitor Bank 1
Max: 0.64843Ratio Min: 0Ratio
Test result value: 0.10156Ratio
PASS
----
MID:$22 TID:$80
- Catalyst Monitor Bank 2
Max: 0.64843Ratio Min: 0Ratio
Test result value: 0.10937Ratio
PASS
----
Click to expand...

So basically it looks like I have 2 failed sensors on Bank 1 Sensor 3 and Bank 2 Sensor 3. I've noticed I get pretty poor gas mileage, it seems to "bog down" a bit and I have to give it a lot of gas for it to accelerate smoothly, and occasionally I'll get a "rotten egg" smell in the cabin on hard acceleration. I'm getting no DTC codes though. The coils and plugs were all changed out about 3k miles ago for Visteons/NGK Plat and VCGs were done, but prior to that I was getting misfires on at least 2 cylinders, although I dont remember which banks they were on.

Basically I'm wondering if it'll be worthwhile to change out these O2 sensors or if this is a sign of the cat(s) being toast. Any input?
 
I have the same rotten egg smell and my local mechanic told me that it was the cats.
 
I have the same exact reading for mine to. I figured it was just a software glitch.
 
Shredicus said:
So basically it looks like I have 2 failed sensors on Bank 1 Sensor 3 and Bank 2 Sensor 3. I've noticed I get pretty poor gas mileage, it seems to "bog down" a bit and I have to give it a lot of gas for it to accelerate smoothly, and occasionally I'll get a "rotten egg" smell in the cabin on hard acceleration.

Basically I'm wondering if it'll be worthwhile to change out these O2 sensors or if this is a sign of the cat(s) being toast. Any input?
Click to expand...

There are "only" 4 sensors; one each pre- and post-cat. The post-cat sensors are just monitors, they don't control anything.
 
There is no bank 1 sensor 3 nor bank 2 sensor 3. That's why those heater circuits have no current draw.
If you had a real problem, your check engine light would be on.
 
Actually, you may still have an O2 issue. O2 sensors can get lazy. They'll still do the job but do it badly, but not badly enough to show a fail on the computer. Poor mileage is a sign of this, especially if the mileage was doing better but suddenly went bad. I would go ahead and replace them with factory replacements and not the Bosch garbage they sell at the parts store.
 
Telco said:
Actually, you may still have an O2 issue. O2 sensors can get lazy. They'll still do the job but do it badly, but not badly enough to show a fail on the computer. Poor mileage is a sign of this, especially if the mileage was doing better but suddenly went bad. I would go ahead and replace them with factory replacements and not the Bosch garbage they sell at the parts store.
Click to expand...

Yeah, all things considered I'm leaning towards one or both cats being plugged from PO driving with marginal COPs for an undetermined amount of time. The rotten egg smell(although relatively minor) and acceleration lag are pretty big indicators of this. I also notice that I lose a lot of power going up hill. Any recommendations for Cats should it need to be done? I read a thread recently eschewing magnaflow and OEM tends to be prohibitively expensive when it comes to cats.
 
Well, I've got a Magnaflow high performance cat on my truck that seems to be OK. Or, if you aren't in California you can pick up a couple of Dynomax universals which I've also run in the past with no problems. A third alternative, you can try replacing them with a straight pipe, then mount the rear O2s in a spark plug antifouler adapter. Sometimes this will give the rears just enough exhaust to keep the computer happy with no cat. Here's a thread that discusses it. I've not done this myself, and it's not guaranteed to work on every vehicle. If you get caught with this in an emissions state you may be fined, and I've heard rumors that if you get caught with no cats in Texas on a Texas-tagged vehicle that they'll crush your car in front of you. I will note that the rear O2 is the only sensor that I feel makes no difference if its input to the computer is altered to keep the computer happy, since its primary function is to make sure you don't remove the cat.
 
Dynomax is made by Walker, and Walker makes OEM replacements for just about everything ever made, so I'm sure you can get a direct fit for it if you want one.
 
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