P0138 O2 Sensor Circuit High Voltage Bank 1 Sensor 2

[rgnjc]

Over the last few days, my 2005 AWD Vibe has had brief low power issues when accelerating after a red light. This would only happen once or twice when the engine was cold and it doesn't happen after warming up. There was no CEL, but my Blue Driver OBDII scan tool found a single error code: P0138 O2 Sensor Circuit High Voltage Bank 1 Sensor 2. See attached images for the error code and the Sensor 1 and Sensor 2 voltages.

Can somebody interpret this? Has the sensor 2 gone bad and need replacing? Is it also possibly my catalytic converter is bad?

I ask about the cat, because over the last year I've been slowly losing oil (see the attached picture comparing oil volumes in my 2 vibes on their most recent oil changes). I do have oil leaking somewhere visible on the engine (rear/side passenger side) which I suspect may be the main oil seal. No oil ever ends up on my driveway though, so I have been wondering if the engine might be burning oil too.

Can somebody advise on how to proceed? Should I just replace the O2 sensor and see what happens in the future? How do I determine if the engine is burning oil and fouled the catalytic converter? Is there a way to determine if the O2 sensor is faulty without replacing it? Also, how do I access the wire plug for the O2 sensor? It seems to be somewhere under the passenger seat but I'm not sure where exactly. This car is at 191k and this is the original rear O2 sensor.

[SeattleJeremy]

That's a big difference. I did 5000 mile oil changes on my Vibe, even though blackstone labs recommended 7000 mile.

[rgnjc]

Normally

That's a big difference. I did 5000 mile oil changes on my Vibe, even though blackstone labs recommended 7000 mile.

Normally my OCI is 4-5k mi, but I recently moved and and have a baby so I haven't had the time. As for the oil leak, I think its coming from crankshaft oil seal. I'm not sure of the seal's GM part number is though so I may have to pull it out and get the number off the seal. I also threw a can of Liqui Moly Oil Saver in for now. Other than the known issues of Toyota engines burning oil (because of the drain holes on the pistons getting clogged), I have no obvious indications that I'm burning oil and fouling the cat/O2 sensor (no soot in exhaust, no smoke, no sulfur smell).

Today my CEL came on and BlueDriver said it was a P0420 (along with the P0138 that I got a few days ago). The P0420 is
Catalyst System Efficiency Below Threshold Bank 1", which I'm hoping is due to the O2 sensor not working correctly and not due to the cat being faulty. I did a temperature test on the cat, front temp was around 500, back temp was around 570, which I think indicates that it is working correctly.

I ordered a GM GENUINE O2 Sensor (2131507) from rockauto.com that should be here Friday. I will start soaking the O2 sensor overnight with PB Blaster, and we shall see if this repairs the issue. Crankshaft seal will have to wait until I find the correct part number for the 2005 AWD Vibe.

[joatmon]

a common oil leak on the 1ZZ's is the timing chain tensioner O-ring, but if yours seems to be from a crankshaft seal, then its probably not the tensioner O-ring.

A 2003 Matrix manual on the sensor 2 gives this test for sensor 2 malfunction (P0136)

Code: Select all

a) Connect the hand – held tester or OBD II scan tool to the DLC3.
(b) Warm up the engine to normal operating temperature.
(c) Read the voltage output of the heated oxygen sensor when engine is suddenly raced.
HINT:
Perform a quick racing to 4,000 rpm 3 times using the accelerator pedal.

Heated oxygen sensor output voltage: Alternates from 0.4 V or less to 0.5 V or more.

I don't have the Toyota doc for P0138



The same manual provides the attached PDF on how to R&R the exhaust system. To pull the rear )2 sensor, it's a lot easier on 2WD Vibes, only do step 6, where for the AWD, you have to do steps 1,2,3,4,5 and 7



decades ago beloved and unfortunately long gone genviber pmh013 had repeated great troubles with cat fouling on her 03 AWD Vibe, obstructed to where she'd have ludicrous loss of power and fuel economy. Not sure if they ever figured out why. Seems like a number of members here have experienced general loss of cat converter efficiency, causing P0420's without any noticeable driveability issues, which they worked around by using spark plug antifoulers on the second O2 sensor.

[rgnjc]

Thanks for that diagram! Huge help for removing and re-installing the wire/plug.

I took a close look at the crankshaft seal and it is not the source of my oil leak. I did replace the O-ring tensioner about 2 years ago, and it didn't look like the source of this leak. It may be the timing chain cover unfortunately, so I hope some Liqui Moly Oil Saver slows or stops the leak. I will need to take a closer look at things, maybe use a dye.

I was able to get the O2 sensor off, with far less trouble than anticipated. Soaked in PB blaster for a few hours and with a little moderate effort and an 18" breaker bar & sensor socket it came right off. The O2 sensor has a small amount of white on it, probably from running lean. Will replace on Friday when it arrives and report back here what comes of it.

While I was under there I did notice the driveshaft center support rubber was torn a bit, which sucks because I replaced it 2 years ago (Anchor Driveshaft Center Support 6097). I don't know why it would already be busted, its possible I didn't align it right and it self-destructed. A little grease was spattered out of the joint too. Probably won't take a look at it till Fall, after this O2 sensor non-sense is solved.

[rgnjc]

Seems like a number of members here have experienced general loss of cat converter efficiency, causing P0420's without any noticeable driveability issues, which they worked around by using spark plug antifoulers on the second O2 sensor.

Not sure I understand the work around here, how do spark plug antifoulers help with O2 sensor readings from a loss of cat efficiency?

[joatmon]

In general terms, (as I understand it, which means I can easily be wrong) the first O2 sensor is used to help regulate air/fuel ratios, while the second O2 sensor is just to measure the converting of the catalytic converter. Computer compares the readings from the second to the first. If the converter isn't doing enough, the computer doesn't see enough difference between the two and throws a 420. Stacking a couple antifoulers backs the sensor out of the actual exhaust flow, which makes it read lower, and the computer interprets this as an indication that the converter is doing its job, even if its not.

viewtopic.php?t=35971 is a recently active thread on doing it

The goal should be to actually get it all working the way it should so we all pollute less, but sometimes money can be a higher short term priority than the important but long term climate concerns. Pretty much why there's a climate crisis in general (if your political stance allows for such a thing that is. Don't want to get into the politics of it all, that's for a different subforum)

[rgnjc]

Short update: I replaced the rear O2 sensor - it was a piece of cake. Plug for sensor on 2005 AWD Vibe was under the passenger seat so I needed to remove seat (4 bolts) plus the radio amp (3 bolts). However, after replacing sensor the car is still losing power when accelerating from stop when engine cold. No codes are being thrown, but issue is still there. Inside of exhaust at the rear O2 sensor hole looked brand new, no soot, oil, deposits, etc. Old sensor looks clean for 191k (see pics). Attached are the O2 sensor readouts+rpms. As far as I can tell everything looks normal (sensor 1 oscillating normally, sensor 2 responds by increasing when increasing rpms and decreasing when letting off the throttle). The only thing that looks odd is a delay when letting off the throttle and sensor 2 decreasing - I thought it should be more immediately responsive. Does this mean its running rich?

I did find a small leak in the exhaust flange donut gasket. I sprayed windex on it when cold and started up. Bubbles started forming immediately (see pic). Leak seems to be minor when idling. This seems like a good way to test for leaks but you only have maybe 20 seconds before the pipe gets too hot and the windex burns off. Will need to replace this gasket, perhaps it is leading to wonky O2 readings and air/fuel mix. Testing catalytic converter temperatures again after driving. Front of cat = 490-500, rear = 550-570. Again, this indicates to me the cat is fine.

In the mean time I'm going to have a local mechanic look at it on Monday to see if there's any other major issue. I will probably replace the exhaust flange donut myself if that's all it is. I can't get to it till next week so I figured I might as well have somebody with more experience take a look at this car in the mean time.

[rgnjc]

*PROBLEM SOLVED*

Here's my conclusive update on this issue: I took it to the mechanic and he said the diagnostic indicated the MAF was faulty and needed to be replaced ($253 for an aftermarket part!). I took the car back and got the GM Original part (88969106) off rockauto.com for $90 and replaced it myself. I didn't suspect this because I kept the MAF clean, since it was a regular part of my maintenance to clean it.

Before replacing it I looked at the MAF sensor with my bluedriver OBD reader. I recorded the live readings of rpms, TPS, and MAF rate. See attached for readouts. Basically, the MAF sensor mostly worked, but every now and then I would get a funky MAF reading that didnt match the throttle position. As I understand it, the TPS and MAF basically overlap mostly, except for a small lag between the throttle position and MAF response. Occasionally I would see a weird MAF reading that didn't match the throttle position, which was causing my slight but noticeable hesitation. The new MAF sensor seems to work perfectly and I've looked at a lot of live readings and everything seems to be working. I added pics here so people have a reference if they ever want to diagnose their MAF with an OBD reader.

I did however get 2 new codes after changing the MAF sensor: P0102 (Mass or Volume Air Flow Sensor "A" Circuit Low) and P0113 (Intake Air Temperature Sensor 1 Circuit High Bank 1). I didn't reset the ECU after changing the MAF, so the computer probably thinks something is funny because it learned the fuel and O2 trims on the old faulty MAF. I cleared codes and drove around for a half hour and they haven't come back.

Long story short: rear O2 sensor was probably not faulty (maybe it was lazy, maybe not), but since it was only $100 I'm not going to sweat it, I look at it as a lesson learned. Replacing the MAF sensor seemed to solve the problem. Car test drives fine and is on its way to 200k! I did however find 2 new problems: the center support bearing rubber is cracked, and the exhaust flange is leaking. I'll fix those next. I can do both, although I'm not sure how to make sure the driveshaft is aligned (I replaced it 2 years ago and it probably failed again because it wasn't aligned perfectly). I'll have to find a shop to do the alignment after my repair. These 2 issues can wait till the fall though.

[JeffW]

My 2004 Vibe with 408,000+ miles usually has P0136 codes when it gets cold outside. Of course, I have to pass emissions testing being the Atlanta metro area by mid-December each year. When on a business trip driving from Memphis on a cold morning (40F) last week Friday, I plugged in my OBD2 reader, and it said P0136 (O2 sensor) I reset/ erased the code. I am pretty sure these us heated O2 sensors, so I checked back every 15 minutes or so while driving and it kept coming back up until the outside temp warmed up to about 58F. I decided I would try wrapping the O2 sensor in fiberglass insulation (non-combustible) and then aluminum foil to keep it from blowing off), then small strips of duct tape for extra support to keep aluminum foil from blowing off - all wrapped from the exhaust up to the O2 sensor wiring. It was 40F the next morning in ATL, when I went on a 40-mile trip for an ATV outing and later that evening to a friend's about 60 miles farther. P0136 never showed up, and OBD2 reads green, so going to get my emissions test tomorrow, Yeah! Coincidence or is the theory correct? Not sure, but maybe try insulating/ wrapping yours in cold weather.

[tpollauf]

Coincidence or is the theory correct? Not sure, but maybe try insulating/ wrapping yours in cold weather.

Nice detective work and thanks for sharing. I'm one of the lucky ones where in NW Ohio there is NO inspection required. That's a very high mileage Vibe you got and hopefully you keep it going to where you hit the half-million mark!