4.7l stuck in limp mode p1126

I'm stuck in limp mode code p1126.
It won't clear with battery disconnect or my crap diagnostic tool. The check engine light will blink off and return immediately.
It's a 2000 Toyota tundra 4x4 frame, box,and 4x4 tranny and 4x4 wire harness with a 2001 2wd cab and cabin wiring, 4x2 ecu, 4.7l V8 iforce.
I used the 4wd transmission computer from the 4wd truck and the 4 hi lo center bezel from the 4wd truck.
I did a water pump and timing belt while it was apart. It started immediately, but through this code and at one time I got the thing out of limp mode and things looked fine but it threw the code p1126 again and I've been stuck there ever since. It says it's a faulting the magnetic clutch circuit but when I test it with 12v it engages and the motor spins.
I'm at a loss. I can't rewrite the vin to a 4x4 ecu because the vin is 2wd, or am I wrong. I need some Master guru with some crazy in depth experience with this road I've gone down. Pins 3 and 4 on the throttle body motor are within specs. In limp mode it has high rpms that climb as the engine heats up. It ran at regular rpms when for that short while it wasn't in limp mode and the throttle was working. I also completely rebuilt the transmission band I'm not sure that's right because I can't fully test it in limp mode. Everything else works or seems to. I've tried a 4x4 ecu but it only cranks and won't fire. I've tried jumping pins 4 and 13 on the OBD2 port. Anyone want to take a crack at some sound troubleshooting advice.

 

Welcome to the forum. I would be guessing to say the mismatched ECU, wiring harness and drive configuration/trans is the issue. But it likely is. I'm not sure what the solution would be, other than get one complete matching configuration installed. Good luck with this, maybe one of the Toyota techies on here can shed some light.

 

Compare ECU pinouts, perhaps pins are switched from one year to another year and possibly 2wd to 4x4.

 

My guess would be mixed harnesses. I’m not sure if the 2wd cabin harness is different from a 4x4 one. But the engine harness and ecu are indeed different.
These older ones done have vins written to them so that shouldn’t be an issue

 

Out of all the text, this one section caught my eye. Not because I know jack shit about anything else you wrote or what could possibly be wrong, but knowing a fundamental concept many modern vehicles use for damn near everything is power, ground, signal wire, the bolded section speaks out to me.

It sounds almost as if a signal wire for the engine temp gauge is feeding into either throttle position, drive by wire sensor (which I don't think exists on your truck year or donor truck year), or similar.

I think you need to be poring over pinouts. I'd start with anything related to the temperature gauge. However, this may be like spearfishing for carp in a barrel with toothpicks unless you have a more competent diagnostic tool....

Piece of advice from someone who's done multiple drivetrain swaps (GenIII LS/LM/LQ) into other vehicles: You always, always, always use the harness original to the ECU, then adapt the extra features from there.

 

Ok, well done. I came to the same conclusions when I couldn't identify any actual problems. So I started repining the harness at ecu. The throttle body is now working. Thanks for getting back to me and so you know, you were all spot on. So it drives, but I think the 4wd harness camshaft and crankshaft sensor wires are spliced together in the wire harness and the 2wd harness has seperate wires for each. Anyway, I don't think it's communicating correctly and is maybe causing the valves to not be right. Or I screwed up the timing belt. The valves get pretty noisy when it heats up. Thanks to everyone for getting back to me and I'm very impressed and would welcome any further advice if you all are interested. Thanks

 

I'm not sure if I'm writing where I should. Replying to my own reply, but if anyone is following this mess,. I have a 4wd harness and a 2wd ecu.
After repining the the throttle actuator wire, I gained my throttle response and the p1126 code went away along with the check engine light. I had also moved the camshaft position sensor wire to the the position that was then open, per my two wheel harness I had removed from the motor and replaced with the 4wd harness. In doing so I the engine had valve clatter and ticking that increased and the oil pressure dropped as the engine became more out of tune. I shut it down and repinned it so that the camshaft sensor wire was in its original place. I let it cool till morning and cleared the ecu with a battery disconnect and shorted the terminals for a few 30 seconds or more. I started it and the valve clatter was there but went away as I started and restarted it. Eventually it settled down. The 4wd harness has the camshaft and crankshaft wires spliced together in the wire loom, whereas the 2wd harness has two separate wires that go to the ecu. My 4wd doesn't engage but I hear the actuator motor.

 

I think you wrote it in just the right place, it's bound to help someone in the future. Glad to see you're making heads or tails of it.

But really, what you just wrote is exactly why I said this a few posts up:

I think you may end up running into other nagging problems using the 4WD harness with that 2WD ECU. But maybe you'll get lucky, or maybe you're better at tracing this type of stuff down than me (I hate wiring diagrams)

 

So, thanks for the follow up. Here's my latest. I was being cautious when I heard what I thought was valve clatter and a crickets in the night sound. As it turns out, the noises were from my exhaust manifold heat shields that are only held on by two bolts each, not the four each as designed. Due to rusted heat shield mounts I elected to when doing the swap to cut that corner and put off that expense until I knew the truck was going to work. My excuses are many but the point is that I was potentially wrong about the valve noises being caused by my wiring at ecu. I'm not sure, but I finally felt comfortable test driving it and I put it through 4 gears. I'm happy to say that it shifted smoothly so far. I did my first transmission overhaul rebuild as well as the valve body. I completely expected to have made a mistake as I had no manuals. I'm not completely sure yet if it's going to work. Time will tell. Tomorrow I look into the 4wd. So up till now the only wire that was different at ecu was the throttle body actuator motor wire.

 

Exhaust bolts rusting away an/or breaking is one of the "5 major issues" documented in one of the 'problems with an early 1st gen' videos I found on YouTube when I started looking into getting one a few years back.

 

I got the 4wd working, the add actuator was corroded some. I cleaned it up and changed the diff fluid. I added my old power seat but used the existing upolstery. The connection was there under the seat but I had no power. I fished around under the driver's kick panel and found an open connector with the same colored wires and when I jumpered them together and I got power to the seat. It's not kosher though. Does anyone know if there is an actual disconnect for the power seats that plugs into the aforementioned connector. Funny thing is, the truck I took the seat out of has that same open connector. Is there a jumper plug that can be used. It's a 2001 base model, my guess is that if I were to upgrade there is a connector that plugs in there and routes to somewhere and completes the circuit from the 30amp power seat fuse.

 

So, an update on my progress, I had a burning smell that was coming from my exhaust. Not one I had ever smelled before. Very acrid and it was like being by a burning coach or some other burning toxicity paint sickness. I couldn't figure it out. I had assumed I screwed up on the tranny or again the timing belt or perhaps some siezed water pump or blown head and spiralling down past a chesier cat and while shrinking in a crooked room I stumbled upon... The power steering pump idle air control valve that if leaking can send atf from power steering pump vaccine lines directly into the air intake plenum where it can combust and smoke internally and find it's way into my cabin through any leaks in exhaust system. I had an extra part and I switched it out. I think it has solved the rabbit hole of wonderland. An alignment is in order and maybe I've gotten through this. Thanks and I hope something in here can be of use.

 

@Gooselake75 more info: https://www.tundras.com/threads/finally-some-good-news.95760/