Do these fuel trims look right for the codes?

95.5 4wd Tacoma 2.7 standard non Cal.
Codes I have managed to interrogate out of it are p0135 and p0141 which are the o2 heaters.
I uhm tested and both are at 0.00 so assume they are bad. Up until recently, I was getting p0420 cat, which I already knew was broke inside but still had good flow. I am waiting on both the sensors and cat to arrive.
So, are these trim’s indicative of those codes considering they are no resistance and not O/L?
Or would there be another underlying problem.

 

Open circuit heaters in the O2 sensors really doesn't affect the fuel trims.
The heaters allow the sensors to get up to operating temperatures faster

 

What is your air intake rate idle vs 2500rpm.......g/sec

 

No idea, this cheap scanner only gives a freeze frame when it pops a code and that is all the data it gives.

 

Difficult to answer your question, what we are looking at are the readings the moment the parameters for setting the CEL were triggered. It doesnt make sense to me. Your codes are related to O2 sensor heaters and your fuel trims are maxed out pulling fuel from the injectors, one has nothing to do with the other. Are there any pending codes? One issue might be when Toyotas O2 sensor testing stragey for the heater circuit takes place, most of the time I get those code within 20 seconds of starting the vehicle, Toyota might check this later on in the drive cycle, I could not find the list of what happens when after you start the truck.

there are other things that modify trims, like mentioned above, MAF airflow. The rule of thumb is that at idle the MAF should show 1 g/sec of airflow per liter of displacement, so yours should be ~ 2.7 ish g/sec. If it reports 10 g/sec, there is a problem.

When you are in enhanced mode, manufacturer specific or what ever that tool calls it when you enter the year make and model into the scanner you are looking at calculated data. If possible rerun your check using generic or OBD settings, this is usually the actual data. Many a time a tech has chased a problem only to realize that the tool is lying to him. The pros have many different scan tools becuase of this.

You have to be careful with scan tools, dont try reading too much into what the tool is telling you, experience will temper your judgement. If the readings dont make sense, change tools if possible.

 

Definitely need to get my hands on a better scanner as I can only get this one to pull codes when cruising. Once I stop, it looses contact with ECU and will either error or show no codes but won’t show the monitors. ( CIL stays lit).
I already tried the clearing method that we used last time to clear out a stuck code which was wiring battery cables together. But no luck.

 

Both your DTC codes P0135 and P0142 indicate each upstream O2 sensor has an issue with the heater circuit. driver side and pax side.

I’m not sure the Toyota code-set criteria. It seems unusual to me that you are in Closed Loop fuel mgmt strategy with those DTCs active.

Maybe there is an alternate PID such as downstream exhaust temp (?) or engine coolant temp that overrides and places the engine computer in Closed Loop.

Regardless, those fuel trims are way out of whack. Like -20 to -25% fuel control?!?!

STFTB1 and LTFTB1

I’m kinda surprised your truck is even running
With the computer pulling so much fuel on Bank 1.

since you already ordered upstream 02 sensors (hopefully OEM equivalent and NOT from Amazon or FleaBay). I would go ahead and replace the O2 sensors, clear the DTCs, and hope that resolves your issue

Deal with the P420 second

 

This truck only has 1 bank and both up and down stream sensors are heated. Actually idles well but has no power and hard miss around 3500 rpms and only getting about 12mpg. Running rich in all 4 cylinders.

 

Duh! My bad!!! I did not pay enough attention to your original post.

OK - reset - why is it running so rich?!?!!

And how are you in CL?

apologies for my boneheaded reply

 

This truck has been a pain the last couple of years. In 2023 I started a thread on the same type of misfires took me a few months to workout just getting this thing to give me the codes. Ended up having to hardwire drain all the capacitors for a few days to get the ECU to divulge them to my reader. Ended up being the cts connector which now has both oem sensor and connector and I see plausible reading for that on the freeze frame.
Currently I have not been able to clear the CEL light again,

 

Ever check your valve clearance? Exhaust valves will get tight over time. I’m assuming you checked plugs/wires? Check for exhaust leaks? Vacuum leaks?

 

Got the 02’s and cat changed out. Looks like that managed to calm the LTFT down but codes are still there, still missing at around 3000 rpm. STFT still out of wack and egr vsv still ticking away before truck gets cranked.

 

Your comment about the EGR VSV clicking before the truck gets cranked. This got me to thinking... the early tacomas have the carbon canister next to the battery and they will make a little burp sound on a regular basis. Try disconnecting the line from the cannister to the motor and see if the trims get better. If your carbon cannister is saturated that would add fuel vapor.

 

Though the vsv that’s clicking is the one under the intake, not the one at the canister, I am going to try this on my way home from work.
I know from the last time when the CTS plug went bad, that if the egr vsv stops clicking it runs great and codes stop