Need wiring wizard!!! 1995.5 5vzfe AUTO 4x4

First post, hope she doesnt turn out to be a doozy.

Truck came to me in shambles. Been cleaning up previous owners jerry rigged bonanza. This wiring is kicking my ass tho.

1995.5 TACO 3.4 4x4 Automatic california smogged. 170xxx miles

I guess the pertinent info starts with for whatever reason factory ignition is basically hot wired inside the collum. The ignition cylinder acts solely as a steering lock out and power all on or all off. Starter is wired to its cactory fuse and to a push button switch inside the cab. Neutral Safety switch has been bypassed

A ton of trivial wires (i.e. washer fluid pump, license plate light,7 factory front blinkers, have been either deleted or re routed to terminals. ) front abs sensor wires have been cut at the knuckles for who the f*$# knows why. Clock spring/spiral cable in steering wheel im sure is broken (no horn, air bag light always on and no cruise control. Cruise checked out in range everywhere but at the wheel) uhh, i think thats it. So ive been chipping away and tracing things fown, repairing cracked wires and missing heat shielding. Soldering and heat shrinking what should have been in the first place. Now todays problem
Check engine light. P0125 engine coolant temp insufficent for closed loop fuel system.
Ok on to the coolant temp sensor, more cracked insulation and exposed copper on the engine coolant temp sensor connector. And the connector breaks when i touch ot to look at said wires. Easy enough. Replace the wires and the 2 piece male connector along with a new sensor while im at it and im feeling good about myself. Codes gone, on doen the never ending line of wores i go.
Maybe 5 miles and w engine starts later Check engine light P0125, back to square one. Ok, test voltage to new engine coolant temp sensor, sensor resostence falls within range according to haynes service manual and my research on these here forums. Ok, make sure connections are tight, supposecoolant level could use a few splashes and a good burping. Do that, clear code, good till the next day. Now i do some rearch, some claim toyota mis-identifies this code, read as P0135 (i think thats what it was) basically bank 1 sensor 1 o2 sensor. That doesnt seem quite right, my rig os dependant on coolant sensor for closed loop system not the o2 heater sensor i believe they were pointing towards. Figure can only be a thermostat or a bad computer at this point. Or MAYBE it is the damn o2 sensors!?
O2 sensors tirns out, more cracked insulation and exposed copper. Ill be damned. Throw the multi meter on them, no short circuit, no open circuit, acceptable voltage coming out of there 4 pin connectors.
The resistence on the Up stream/bank 1 sensor (the one with the heater that may or may not be involved in my engine code discrpency is within range. On the edge of tolerable but in none the less.
Bank 2 /downstream sensor. Id bad. Dont care, (Southern Oregon. We dont have emissions here) not at all involved in the code i have now. Code remains only a P0125. Nothing else. Not the bad circuit codes or O2 codes.
So put a new orileys thermostat and gasket in it. Full coolant flush and fill, i had recently already replaced RAD hoses, radiator cap and confirmed water pump has good flow. Double check all my fuses with a meter invase i missed something visually. All are ok.
I dhould mention temp gauge on dash had always and continued to take appropriate time to reach operating temp and stay dead nuts in the middle of gauge. Heater blows hot and idle drops after a few minutes.
Check engine is gone, truck seem happy. Got it.
Till the next day. Same code same coolant tenp sensor. WHAT THE FUCK!?
Bitch and moan and dinally get around to starting from scratch at the ecm and testing volts down the line and at every intersecrion, splice and terminal on the shared wires that run to the ecm. Over 14 volts all the way to the coolant sensor, including the coolant sensor and past it down to the end of that circuit. Test all the realays and sensors my coolant sensor shares its power with. Those all test fine. Only thing i can think now is is my ecm fucking up?
Went through today and fixed up the wires to both my o2 sensors. Bank one works. Scan tool data on its monitoring systems function reads bank 2 o2 sensor not ready. Kneew this one was bad, shouldnt be related to my problem, no code for 02 sensors still. HO2S (bank 1 with the heater) good.
So CEL is off again after all that. And stayed off for almost 30 miles of driving. Great! Fixed it!
Then suprise!!! Check engine light. P0125 coolant temp sensor.
Yadda yadda yadda. Same code. Went through the scanner tests and down trream o2 sensor heater is now stuck on 'not ready' a.k.a.fucked.
Short of replacing the downstream sensor. or i had figured unrelated i would be deleting downstream o2 and using resisters with the upstream o2 '/ and tricking the computer by showing it the resistance on both circuits it wants to avoid the code p- o -4 -whatever it is you get for a code when you cut the cats out of the system and maybe it will solve my current coolant temp code in the process?
Only now, the next day, scanner says ho2s is good again, and check engine light is not on and there are no codes. Dont know why or what made the engine light go off and it to finally go into closed loop mode and stop running rich. Or why its not telling me about the o2 sensor that i know is bad. But since it was all good it has resorted to "ho2s not ready" with the check engine light about the coolant sensor again. I ignored it let the truck idle for a long time while fine tuning subs and amp and head unit. After probably an hour of idle scanner says ho2s is good and my light it out again on the dash.
My question it what the hell is going on? There is not detectable short or open in the circuits. The Ho2s in question tests as functional and yet doesnt behave anything like the way it should. Im out of ideas. Far as i can tell electrical is fuctional as is. (Albeit not built to last in a cpl places but damn sure good enough to work.
Idk. Anyone have any sort of idea here to look next? Ecm? Ecu?
Can that ho2 sensor be fluctuating within spec range 99% of the time and test good but then dip just far enough out of spec for the closed loop fuel system to detect him but manage to not set off an o2 code at the same time? Grounds and positives are all just fine to and from all of these sensors. I can find no bad fuses, no bad relays, no loose wores in backs of connectors, no broken or corroded pins in sensors. No parasitic drain. Battery holds consistent voltage. Alternator puts out 14v and some chain
Any input greatly appreciated at this point.

 

You will drive yourself insane trying to figure this out .

The Factory Service Manual or at least the Electrical Wiring Diagrams in your hand.

 

Is the cooling fan clutch stuck engaged? Cooling fan spinning full blast all the time?

What is the coolant temp reading while driving? Not the gauge but the scan tool reading

 

Not sure temp while driving. Cheap scan tool doesnt read vitals like that. Only dtc and sensor readiness. Jeater goes from cold as heck to nice and toasty though. Heater blower motor not blowing quit as well as it should. But more than adequate
Clutch fan always spins. Does gey audibly louder when motor heats up.

 

I have the haynes manual and factory witing diagram pdfs downloaded. Thats how i got this far

 

Really need to get a reading of what the computer thinks the temperature is to go further. do you have an infrared temperature gun like a Raytek? It would be nice to have a reading at the upper radiator hose to compare to the gauge

 

Are you sure you are replacing the correct sensor? There are 2, one for the ECM and one for the gauge on the dash.

https://www.tacomaworld.com/threads/3-4l-efi-engine-coolant-temp-sensor-location.419900/

 

Yup, 2 wire is the one ive been fucking with. I havnt even looked at the other one. Is it possible that if the wiring to the sensor for the dash is funky it could interfere with it? Or if that sensor is bad would it interfere with the closed loop system or it would only mess with my gauge?

 

Bump

 

Ok I pulled this from my FSM (I only have info for the 3RZ, but most of the things relate)

"To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three−way
catalytic converter is used, but for the most efficient use of the three−way catalytic converter, the air−fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air−fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the
stoichiometric air−fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and provide
feedback to the computer for control of the air−fuel ratio.
When the air−fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen
sensor informs the ECM of the LEAN condition (small electromotive force: < 0.45 V).
When the air−fuel ratio is RICHER than the stoichiometric air−fuel ratio the oxygen concentration in the exhaust
gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: > 0.45 V). The ECM judges by the electromotive force from the oxygen sensor whether the air−fuel
ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sensor
causes output of abnormal electromotive force, the ECM is unable to perform accurate air−fuel ratio control.
The main heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled
by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to
the heater to heat the sensor for accurate oxygen concentration detection."

After engine is warmed up, heated oxygen sensor (bank 1
sensor 1)output does not indicate RICH (> 0.45 V) even once
when conditions (a), (b),(c) and (d) continue for at least 90
sec.:
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 ∼ 100 km/h (25 ∼ 62 mph)
(c) Closed throttle position switch: OFF
(d) 140 sec. or more after starting engine

P0125 Possible Causes

• Air Induction System
• EGR system
• Fuel pressure
• Injector injection
• Gas leakage on exhaust system
• Open or short in heated oxygen sensor (bank 1 sensor 1)
• Heated oxygen sensor (bank 1 sensor 1)

First thing says to check voltage on your upstream sensor, which you did.
It also notes that if the vehicle runs out of fuel, it AF will go lean and throw P0125

Then check for for short in harness between oxygen sensor and ECM.
There could be a bad connection somewhere which is causing your intermittent results.

Check for misfire

Check air induction systems

Check EGR (does the 5VZ have this? I can't remember)

Check Fuel Pressure

Check injector injection

Check gas leakage on exhaust systems

 

So ecu says i have 0 volt at both o2 which i know to be false. I read voltage with meter.will say 'ready' for o2 heater test. Catalys and o2 stay 'not ready' temp reads right around 190. B1S1 o2 trim has a reading and i got it to go into closed loop system. But even after around 70 miles of highway/some town driving, more than 2 starts and a cold start the p0125 code came back on WHILE THE TRUCK WAS IN CLOSED LOOP!! fuel effeciency reading was 1 (whats that supposed to reat by the way?)
Timing advance read normal, fuel trim B1S1normal. B1S2 0% trim.
I will screen shot my ecu readings here in a bit when i leave for work.

Any idea if this seems like a bad ECU, or an open/short to O2 or a faulty o2 or a combo of?
Definitly have some wiring gremlins in the o2 wires. But how do i know if the ECU id acting up
I got my hands on FSM wiring and a bitching pin out of ECU from a member here.

 

UPDATE
engine temp comes up to 190 +/- as it should.
Both o2 sensors read voltage and pulse within spec with a multimeter on the sensors.
Both O2 and O2 heater wires are reading sufficient voltage at the ECU pin.
Engine light less frequent but will still occasionally come on with P0125 insufficient coolant temp for closed loop fuel while scanner says it's in closed loop.
Scan tool says my ecu reads 0v on both sensors at all times. Not even a blip. yet it completes emission tests and says 'ready on the live data' ecu is trimming fuel and entering closed loop while reading 0v on the live data. I've checked every sensor, relay, fuse I can think of. They're all fine. Tried to wiggle and bump every combo of wires to make it short out. It won't that I can find. Have no opens in circuit.

Found a couple pin holes in vaccum lines and sorted those out. No change.

Idles fine. Cold and then warm.

Catalyst test won't complete on the live data and I have a pretty decent rattle from the cat converter between o2 sensors at random intervals but goes away with any amount of throttle.

Throttle only reads about 80% at wide open but tps tests within spec and wiring to it is all sound
Everything related to intake is new/recently cleaned besides the plenum itself.

Could it be the wire between my ecu and obd2 port? Is that how those work? I'm stumped. Someone please help. Idk what to do from here.

 

Well, fuck it. I'll figure it out now. I'll report back for all you eager fucks.