P0141 and p0170 codes and black liquid in exhaust

The p0141 (O2. Heater circuit bank 1 sensor 2) and p0170 (Fuel trim bank 1) codes are through on my 95 Tacoma. I am also having a black liquid come out of my exhaust. That truck has 145k miles on it so that paired with the black liquid I’m thinking that I’m going to need to replace the cat. That still leaves the heater circuit and fuel trim code being thrown. How can I fix these?

 

That black liquid is probably just condensation with soot in it, doesn't mean the converter is bad.

Look for any intake leaks like a rotted vacuum line. Clean the maf sensor, check fuel pressure with a gauge. You could reasonably throw a new sensor at that 02 heater code

You'll need some troubleshooting skills and a code reader that displays fuel trims to go further

 

By any chance do you know what normal fuel trim is so I can check it

 

Less than 4-5% plus or minus

 

+/-10% Total (short term + long term) trim is considered normal
Not sure how much data you can look at on a 95 but coolant temp and mass airflow sensor would be other data you would want to look at.

 

My mass air flow is reading about .45lb/min at idle and my O2s are both reading 0(V)

 

Even when I give it gas my o2s b1 s2 is getting 0 volts but sensor ones is getting voltage

 

Mass airflow is about right if you have a 3.4l, upstream O2 should bounce between about 0.2-0.8v when the truck is in closed loop.
The downstream sensor reading 0 isn't surprising since the heater isn't working in it, an O2 sensor has to be around 700 degrees before it will function.

 

It’s a 2.7l. It was reading stft b1 as 19.5% and ltft b1 as 23.4%. Could it be running so much fuel because the heater isn’t working right at first start? Thank you guys for your help

 

Those are really high trims. It's trying to add fuel to correct a lean condition. Or at least what it perceives as a lean condition

Look for vacuum leaks
Check fuel pressure
Maf is also suspect

The downstream oxygen sensor can sometimes affect fuel calculation. Try unplugging it.

 

so should I fix the heater circuit then go from there or is it my heater circuit that’s causing the high fuel trim

 

Heater circuit codes are really common and usually don't affect fuel trims. But I guess it's possible.

Dm what do you think? Could a heater circuit short into the sensor circuit and give dirty info to the pcm?

It's probably had the heater circuit code for a while and then something else is causing the lean condition

 

I have cleaned out my MAF already and erased the codes but it only last a couple days before the were back

 

My under is that, Low O2 voltages typically mean there is Lean condition.
When the ECM sees this, it adds fuel. Which coincides with the high fuel trims.
But 0v?

I find it unusual that both are reading 0v.
I’d check the heater circuit.

 

I have seen a bad heater on the upstream sensor cause issues but being it's the one on the downstream sensor it shouldn't affect fueling.
MAF g/s (lb/min x 7.56) should be about equal to engine displacement in liters at a hot unloaded idle (700-800 RPM)
If there's no obvious vacuum leaks I would really want to check fuel pressure.
How does it run otherwise, do the fuel trims improve while driving or get worse?
You can test O2 sensor operation by inducing rich and lean conditions by pulling a vacuum hose off (O2 should go low <0.2v) and then spraying carb cleaner in the intake O2 should go high (>0.7v).

 

The truck runs good when it is being given gas but is still a little high. It sometimes has a little studder when it is idling. I’m only driving it about 15 miles to school and back so it doesn’t seem that it is getting up to operating temp. I have had the cab off of it not to long ago, could when I was putting the cab back on could I have pinch a wire and cause the heater circuit to fail completely for the downstream sensor?

 

If it only hiccups at idle but has good power when you're driving around normally it's probably an intake leak

Check the intake boot between the math sensor and the throttle body really close for cracks . Check all the vacuum lines again and listen for hissing seconds

Spray some carb cleaner around and see if those fuel trims change

 

It's a possibility, never hurts to double check your work.
Just to be clear is this a 95 or 97 truck, your profile says 97?

 

95 Tacoma 2.7l manual 4x4. I don’t know how to change it on my profile

 

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