Not your average p0157. Please help.

My bad, what I mean is there was a violet wire hanging out of the junction, I'll have to double-check if it was PA11, and the the violet wire hanging off PCM e5-8, and I taped those together, but where the violet was hanging off the junction, the yellow/black was the pin below it. I'll take a pic tomorrow This is where I was under the impression that they junction together.

So when I give the sense wire power and it jumps them baselines at .015, am I spoofing the system then? Cause I was under the impression they stayed at 0 until the heat kicked in as well, which is what I saw when I initially began testing. I've I never give the sense wires voltage, they will stay at 0 until the engine is running for a few.

Yea that's where I'm at right now. Half of the taped splices that I've found so far don't make sense for an engine swap, I'm thinking the harness probably got yanked on when they pulled the engine, which I'm dreading cause that means the issue is probably tucked down behind the engine since I haven't found a break in the sense wire sheath yet. But I can't imagine I pulled on any of the wires under the dash or by the fire wall hard enough to make it that far down the loom. Idk. If I cut that sheath open to inspect, would I be able to just tape back over it with the shield wire tucked in there? Or would that ruin it altogether? Hell I'm almost getting ready to just buy a length of shielded wire and run my own sense wire from the pcm down there to do a hot fix. I don't wanna do it sloppy like that, but Im not equipped to pull the engine back out lol.

 

The wire you have circled here is Black/Yellow and that is at the Park/Neutral Position Switch.
The Yellow/Black wire at the Junction Box (PA Pin 10) is the L4 signal to the PCM.
Below is the pinout for PA (at least as far as I've gotten), working on pinouts for all junction connectors.

If you do they bypass test with a test light the signal should change regardless of engine status, I was saying if they are connected they will stay at 0 until they get up to temp because an O2 Sensor makes it's own voltage but only once it get's up to temp.

Could have been damaged in the collision as well but yea looks like a hackjob repair. You could run an overlay but I don't like doing that unless there is no other choice because typically when there is a broken wire in a harness there is other damage in that area.

 

Huh, okay. I'll double check tomorrow. Everything shifted fine and 4wd hi low and difflock all went into place just fine so I should be okay. Still odd that the nsw is completely cut and there's no indication that the ecm is having trouble with that.

I pulled the tape back off just Incase. When I popped the junction backside it looked like there was just a connection going straight up and down bridging 10 and 11, but there were bridges behind those as well, thats where I was getting hung up on that idea. Also that pinout sheet is badass!

Ahh okay I see. I was aware the heaters were to speed up the process until the heat from the cats kick in, I just didn't know at what point the sensors start putting out a signal. But I'm just getting hung up on why if I give the sense any sort of voltage, even for just a second, lower and hang at .015 instead of dropping back down to 0, regardless of anything else. Well at least until the working sensor gets up to heat.

I'd definitely rather not do this if I don't have to. But I do have to get this title in my name soon, and it might have to just be a temporary fix if I can't get the emissions system ready in the next few days. The good news is it only appears to be that sense wire as far as the O2 sensor goes. Heater voltage and ground have been consistent with their connection, idk about the heater control wire as I'm not sure how to test that just yet, if I'm understanding right that shouldn't give off voltage or ground right?

 

I don't think it would set a code for not seeing a park/neutral input, still not sure why they would have cut it.

The junction is essentially a box full of jumper wires.

They have to reach about 700F before they start working

Not sure what that's about, so you say if you touch the sense wire with a test light the voltage get's stuck at 0.015?

Ah so you have to have the monitors run and pass to get your inspection where you are?

It would set a heater circuit code if the heater circuit was open or shorted and the sensor would eventually get up to temp driving even without the heater.

 

Yea, so like if I have the key to just on, not turning over the engine, they start out at 0 on the live data, like normal, but if I touch voltage light to the sense wire, at least on obx2, it jumps to like 1.2xx and then falls back down to .015 instead of 0, when I remove voltage. I wanna say it did this on obx1 side as well but I can't remember now. But when I had everything wired back up initially, they both jumped to .015, without me giving any external voltage, and that was with obx2 still disconnected at the pigtail. I connected obx2 and drove around, and obx1 climbed as normal, while obx2 stayed at .015. it wasn't until I separated the shielding again, that they both went back to 0 after turning ignition off and back on. But if I give external voltage, it does it again.

Yea, California, super stupid strict. Don't love it here. Any little thing will fail you, regardless if it's not emissions related.

Ah okay, so if I'm not seeing a code for that it should in theory be working properly then?

 

It may be some kind of default strategy since it's not expecting an O2 signal with the engine off and also it's not expecting to see that high of voltage on the sense wire.

Ah yea that sucks.

Correct.

 

Okay I think I found the break. I went out at it again, but didn't get much time cause it started raining. Obx2 started out at 0, obx1 started up with .015 oddly. This is all with the shielding not grounded. Wiggling around the wires where they come out of the firewall made the voltage for obx1 fluctuate and hold at different voltages(engine off, ignition on). Went back down under the dash, and started wiggling around, obx2 still had nothing. Then I twisted the pcm and obx2 got 1.2xx volts from the test light at the pigtail. If I twisted it to the left, it dropped back down, but to .015, if I twisted to the right, it held 1.2xx. Entirely possible it may be the pin itself? The wire looks solid unless there's an internal break somewhere that I can't see because the wire itself has no faults to it. Not too thrilled about trying to depin the plug if that's the case, but at least it seems I've located the hotspot.

 

It's possible especially if someone was poking around in the pins with meter leads.
Alot of times you can visually see terminals that are spread but the best test is a pin drag test.
They aren't terribly hard to de-pin, just have to do 1 at a time and remember what slot they go in.
The file below shows how to disassemble most Toyota connectors.

 

Well I couldn't get the pin out, I don't have any suitable tools to hit that keyhole right. But I stuck a pin in the backside and was able to lock it in. Finally have voltage running to the pcm steadily. Drove around for a bit and it registered the O2 sensor was sending signal. Bank 2 was fluctuating like crazy though while bank 1 was holding fairly steady lines. I don't have the shields grounded so there may be some interference at play, or it could be the pin..


I can't imagine it's the sensor itself since it worked fine on bank 1. I didn't get a code for low voltage this time, but I did get a p0430. I wanna say this is probably from the fluctuating voltage and not that the cat is bad. At least I hope not haha.


Also got a code for the transmission range circuit, this would most likely be from that cut NSW wire right?


Slowly but surely getting there, I think lol

 

Bank 2 looks like a normal O2 sensor signal with a failed catyletic converter so no suprise you got a P0430, bank 1 looks good.

Yea the range sensor code could be from that or another part of the range circuit it's not happy with, I'll have to look up code set criteria for that one.

 

Dammit, one thing after another lol. Doesn't seem like an interference issue then huh? It started raining again, so I had to quit. But I'll go out tomorrow(or today if it stops) and ground the shields, connect the nsw and go from there. I'm starting to see why this truck was so cheap. Crazy that everything is happening to bank 2 side though.

 

I mean it could be but it doesn't look like it, you could do a WOT run and then decel fuel cut and see. They should both stay rich (>800mv) on a WOT pull and drop lean (<200mv) on a decel fuel cut.
Yea cheap vehicles alot of the time aren't so cheap to get back into shape but when you consider what Tacos go for in good condition with a good frame regardless of age or mileage it may be worth it.
Kinda sucks that you are in California and have to use California compliant converters.

 

I did hop on the freeway and gas here and there, and for whatever reason, a few times actually, both sensors dropped to .015 for a few seconds and then would pick back up. I recorded the whole trip. I thought it was blips in the live data, but watching the play back the #1 sensors did not have the same reaction.


Was odd to me that bank 1 had a slow steady climb back up on the graph line while bank 2 just shot right back up.

That was my reasoning when I bought it, I figure whatever I put into it is worth it in the long run, especially with the prices they're going for out here. Lots of salvaged with 270k on the clock still asking for 10k non 4wd, and that's just the 1st gens lol. My 05 runner I built up just got totaled, and I wanted to try the tacos out, but I needed to do it on a budget. So I half expected a lot of issues. I've never had to deep dive into electrical like this before though, so it was a bit overwhelming at first lol(you've been a huge help btw). Everything else I know I can fix.

Yea, if that wasn't the case I wouldn't wince at buying a new cat just to see. Everyone knows it's just a money grab by the state, like most of its regulations. Hoping to be out of here within the next year or so lol.

 

Hard to confirm downstream sensor operation without seeing what the upstreams are doing, that's why I said do a WOT and decel. At WOT the fuel ratio should be rich which should drive the downstreams full rich, a decel fuel cut will be lean so they should go full lean until the injectors come back on.

Yea at least electrical is relatively easy to repair if you can find and repair your own problems, if it does need converters though that could eat pretty deep into your budget unless you could find some used for a reasonable price.

Looks like P0705 sets when 2 or more position switch inputs are on at the same time or none are on so yea it could be caused by the Park/Neutral wire being open.

 

My bad, I've got the voltages for those too. When I went wot the upstreams shot up while the downstreams dropped down to the .015, as I deceled, the upstream voltages dropped while the downstreams climbed. This happened a few times, but wasn't consistent. I'll do another drive test tomorrow and get some better readings with more accurate snapshots.

This is accel





This is decel

If it comes down to that yea I'm hoping that too. Probably try to find a wrecked part out or something. I'm hoping it's just a one off. Truck was relearning everything and running pretty rough while I was driving since I had the battery disconnected and the pcm unplugged. Probably should have let it idle for a while before taking off. But that's just wishful thinking lol.

Oh for sure, thanks! I'll double check the pinout at PA and reconnect the wires tomorrow and see if that changes anything.

 

I think you need to add TPS & RPM in there, I'm pretty sure the decel is in the section I marked. If it's not your scan data is goofy or it's really lean on a WOT pull.



AFR Sensor


O2 Sensor

 

Hmm, yea, seems like they're backwards in my scan if that's the case, I'm sure I probably read it wrong trying to look at it and navigate traffic simultaneously. I'll add the parameters and do some more pulls tomorrow.

 

Yea that's problematic, need to determine if the sensors are working right though.
Adding TPS and RPM should allow us to know the relation of the sensor signals to the throttle though.
I'll try to get a capture of mine tomorrow if I remember so you can see what normal looks like.

 

Honestly at this point if they weren't working properly I wouldn't be surprised lmal
Will do, thank you!

 

It is cool that you have stuck with this.
Even cooler that you’re going to get graphs.
I haven’t followed this one close, but I need to go back and read it from the start.
Lost of good info here.