P0135, P0141, P0155, P0161, all four o2 sensor codes at once

[frawstme]

Hello, I got all four of these codes at once:

P0141 – Bank 1 Sensor 2 Heater Circuit
P0135 – Bank 1 Sensor 1 Heater Circuit
P0155 – Bank 2 Sensor 1 Heater Circuit
P0161 – Bank 2 Sensor 2 Heater Circuit

I cleared them, then they came back when I checked again (about 5 drives, ~20 miles). For context I do have aftermarket high flow headers and cats, but I don't think that's the cause. The cats do have downstream spacers. I really am not educated on o2 sensors but from the research I've found online, the spacers shouldn't effect the heater circuit at all.

All of the sensors have voltages in line with where they should be:

• B1S1 = 0.075 V
• B1S2 = 0.820 V
• B2S1 = 0.135 V
• B2S2 = 0.860 V

Fuel trims are nearly perfect-
Bank 1:

• STFT = -0.04%
• LTFT = -3.16%

Bank 2:

• STFT = -0.04%
• LTFT = -5.50%

What would be recommended next steps for this? I understand the system but I am not educated on diag

Thanks in advanced

edit:
probably unrelated but I also have "VERY LOW" as the value for ECU IG power

 

[OEMGUY0720]

1st question since you mentioned you have AM headers and catalytic converters, do you have new or old (how many miles/years) upstream and downstream O2 sensors? Any chance you have a picture of the probes?
2nd question, have you tried an exhaust leak test (soapy water and spray bottle method on all connecting ends of your exhaust system from headers to outlet?

 

[frawstme]

1st question since you mentioned you have AM headers and catalytic converters, do you have new or old (how many miles/years) upstream and downstream O2 sensors? Any chance you have a picture of the probes?
2nd question, have you tried an exhaust leak test (soapy water and spray bottle method on all connecting ends of your exhaust system from headers to outlet?

The sensors are original, 104k miles and it's a 2000 model. I did inspect them, they looked fine but unfortunately I don't have any photos on hand. The tips were light brown.

And no sir I haven't tried any leak tests. I thought that leaks would be a different code unrelated to the heater circuit

 

[ceylonfj40nut]

My son’s 100 series had similar codes on original TEQ cats (320k miles). He did a PhD on it trying to figure out cause. It did not smell like cats not working. Car drove without issue. Turned out the gas cap was not tightened to three clicks most Toyota’s need. Similar has occurred on my wife’s GX460. Sharing. Check the gasket on your gas cap. If it is cracked or stiff, replace. Three clicks.

 

[frawstme]

My son’s 100 series had similar codes on original TEQ cats (320k miles). He did a PhD on it trying to figure out cause. It did not smell like cats not working. Car drove without issue. Turned out the gas cap was not tightened to three clicks most Toyota’s need. Similar has occurred on my wife’s GX460. Sharing. Check the gasket on your gas cap. If it is cracked or stiff, replace. Three clicks.

Lol this is going to sound stupid but mine does not click three times, it's a different mechanism than American models. By design it's one hard click then impossible to turn any further. I'll inspect the gasket though once I get out to my car

Do you know what other diag he tried in the meantime?

 

[TahoeZ]

- Replace gas cap with OEM (one click is sufficient when tightening)
- Try replacing a sensor. O2 sensor failure is very common and, yes, they can all fail/throw a code at the same time.

 

[frawstme]

- Replace gas cap with OEM (one click is sufficient when tightening)
- Try replacing a sensor. O2 sensor failure is very common and, yes, they can all fail/throw a code at the same time.

okay. I'm assuming only go OEM with these sensors? They're kind of expensive

And are you saying to replace one, then if the codes go back try to swap out a different one until I've gone through all four?

my cap looks in good condition..I can order another but it'd come from Japan so it'll be a few weeks before I can confirm that is or isnt the problem

 

[TahoeZ]

I would replace one upstream and one downstream.

Do you hear a pressure release when you remove the gas cap?

 

[frawstme]

I would replace one upstream and one downstream.

Do you hear a pressure release when you remove the gas cap?

Yessir, I can take a video of that. I'm used to driving newer cars so it caught me by surprise first time I opened the cap

 

[OEMGUY0720]

The sensors are original, 104k miles and it's a 2000 model. I did inspect them, they looked fine but unfortunately I don't have any photos on hand. The tips were light brown.

And no sir I haven't tried any leak tests. I thought that leaks would be a different code unrelated to the heater circuit

The codes you have refer usually to a general misfire, I see your LTFT has a negative readout. I wouldn’t rule out the O2 sensors but will prioritize checking all the spark plugs if they are tight to factory spec and check the tips for any heavy carbon buildup, the ignition plugs if they are browning or case of possible oil intrusion, the intake manifold and the MAF sensor for any loose connections/vacuum leak. Normal LTFT readouts always have a positive value, a negative value present a rich air-to-fuel mixture which is related to the errors you shared.
Here’s a realtime STFT and LTFT for example

 

[frawstme]

that wasn't my understanding of how it works at all, lol

Maybe because it's a different brand but in my shop anything less than +/- 5% is considered borderline excellent, you want it as close to 0% as possible. +/- 10% and greater is where red flags start to go off

I thought that if it's positive or negative only determines if the ECU is adding or removing fuel depending on if it thinks the engine is running rich or lean based on what it's learned from driving habits

In your screenshot, you've got a positive 10% value which means the engine is having to add an additional 10% fuel at all times to run where the ECU thinks that it needs to be

My negative 4% is just meaning that it's learned to remove a small amount of fuel which presumably is from the MAF being dirty or maybe some variation in injector flow

Full disclosure i might be wrong but that's the way I've understood it to work / the way I was taught that it works

Worth noting that I do have new spark plugs but I'm unsure about the injectors, not sure how difficult that is to check on these but I'll look into it shortly

 

[white_lx]

edit:
probably unrelated but I also have "VERY LOW" as the value for ECU IG power

This "VERY LOW" indicates a voltage drop somewhere. If there is voltage drop in the supply or ground side to the ECM, none of its measurements are valid. Start with fixing this. Given your fuel trims are within spec, the sensors are probably fine. Start with power and grounds at the ECM while running. Also check the O2 heater fuse.

 

[frawstme]

This "VERY LOW" indicates a voltage drop somewhere. If there is voltage drop in the supply or ground side to the ECM, none of its measurements are valid. Start with fixing this. Given your fuel trims are within spec, the sensors are probably fine. Start with power and grounds at the ECM while running. Also check the O2 heater fuse.

oh boy, sounds like a nightmare on this car

Any idea which fuse might be O2 fuse?

See the bronze wires around my fuse box btw? There's like 20 running around my bay, almost everything in my car is grounded to the same point

 

[white_lx]

"20A EFI or ECD" fuse feeds the oxygen sensor heaters (top left). Turns out the MAF and a few other things use the the same power circuit. So if the fuse would be bad, I expect other codes too. Check the voltage at both terminals of the fuse to battery ground (directly on the terminal) and to chassis ground. That would be a good start without opening up anything other than the fuse box lid.

 

[frawstme]

"20A EFI or ECD" fuse feeds the oxygen sensor heaters (top left). Turns out the MAF and a few other things use the the same power circuit. So if the fuse would be bad, I expect other codes too. Check the voltage at both terminals of the fuse to battery ground (directly on the terminal) and to chassis ground. That would be a good start without opening up anything other than the fuse box lid.

I did this, and actually checked the voltage of every other fuse too. Everything was good. After that I installed new battery terminals and cleaned all my grounds (which seriously, that was a task).

Also cleaned my MAF sensor and throttle body, the TB was absolutely filthy and gunked up. Im sure it doesnt have anything to do with the codes but just curious if it will level out my LTFT even more over time.

Went through and double checked to make sure none of the o2 sensor lines have gotten damaged or melted since relocation from the header install. Everything looks pretty good.. im hesitant to buy new o2 sensors but it's looking like it might have to be the next step

As of right now techstream shows everything as normal, but I've only driven the car 4 miles since having the battery disconnected. I'll see what it says over the next few days. The "VERY LOW" indicator isnt there, but the box is also blank. This is a side effect of the vehicle being japanese, many boxes are blank for me.

 

[white_lx]

Those codes are 2-trip logic. So it should take 2 drive cycles for them to show again, if still present. But after a single trip they would be 'pending'.

The missing low voltage indicator is a good sign. Did you find any suspect connections? What is the voltage at the ECM, vs at the battery?

Before purchasing new O2 sensors, I would at least confirm the presence of the battery voltage at the black-yellow wires of the connectors of each oxygen sensor (assuming the Japanese vehicle has the same wiring colors as North America). You can then also check the O2 heater resistance. All 4 throwing error codes points to something else than just the sensors - unless they all failed at the same time....