2001 TUNDRA P1126

Help, has anyone ever actually fixed the throttle body issue with the early Tundras? I have found thread after thread with really good information on checking this and that but I have yet to find one that show a fix. There have been a few where it was a simple fuse , but that is not the case with mine. I have had both fuse boxes out of the truck. I have replaced the PCM and the throttle body assembly with new parts. I have traced every circuit. I did find that I don't have 12v at the blue wire with black tracer at the throttle motor but cannot find any information on a fix. Is there anyone who has a solution?

 

Hopefully you're still around. I just spent an insane amount of time fixing my own (link here).

To answer your direct post first. I don't think that you should be getting 12V on the wire you mentioned. The Factory Service Manual, at least for my truck 2002, show that as a signal that oscillates on 5v.

I'll probably repeat a bunch of stuff here you've already done, so forgive me, but here's how I would approach it:

1. Check fuses/rusted pins simple stuff
2. Check all the pins are in the right spots (Acceleration Position Pedal Sensor/APPS, Throttle Position Sensor/TPS, and Throttle Control Module/TCM). EWDs are available here.
3. Unplug the battery, unplug all the connectors, and check that the correct pins have connectivity end-to-end using a multimeter. It's a long reach so you might want to buy some alligator clips (youll probably want also some thin pins that fit into the ecu connector gently).
4. At this point, if you have a half decent diagnostic tool (I had a cheap Harbor Freight one Zurich ZR11 I think?) or access to TechStream (the toyota diagnostic) I would plug everything back in, and make sure the voltages look correct through the entire travel of the acceleration pedal. For more information about this I would check the P1120 DTC which talks about normal operating voltages.
5. I would also check the TPS by just pulling off the plastic air intake and slowly moving the butterfly throttle by hand and making sure you can see that change on the diagnostic (I think normally they just give something like "throttle percent open")
6. If either of those were bad you would probably have a different engine code, so now the meat of it. I would test the throttle motor independently. There's a guy who shows this on a Lexus. I took my whole throttle body out and tested it using a bench power supply with 5V which was enough to engage the clutch and run the motor (another reason I don't think you should be seeing 12V on the blue/black line).
7. If you see a lot of carbon around the butterfly/throttle opening at steps 5 or 6 you should remove the throttle and clean it (i think either Mass Airflow Sensor or Carb/Throttle specific cleaners are fine. I used both on mine and it still works)

If you get through all this all the following SHOULD be true.

• Your system has power. (1)
• Your wiring is correct and goes to the correct places. (2-3)
• Your computer is reading all it's inputs correctly (4-5)
• If given power, your TCM will throttle correctly. (6-7)

To be a bit of a nerd for a second. DTC P1126 is basically "Hey I can't operate the throttle." The FSM for 2002 says it triggers essentially if there is an over-current or under-current condition. Over current is likely if the throttle is trying to open but is experiencing resistance, under-current means the car can't supply enough (or any) voltage.

If you have access to techstream you SHOULD be able to find out which one is your problem in the ETCS data list with the "magnetic clutch current" value.