Interesting. The TB on the 2013 failed before the one on your older 2007. So you believe you got a short in a capacitor within the control circuitry, allowing an unmodified voltage signal to pass through? Makes one wonder. So if it is a capacitor faliure, did a high voltage transient at one time cause a dielectric breakdown within one of those tiny control circuit capacitors or was it a slow fail due to a manufacturing defect? Failures in TBs are relatively rare, fortunately. How many miles on the 2013?

 

No idea why it quit. 226k miles on the 2013. 179k on the 2007.

All I know is I have 4.8v at the VTA1 terminal. The ecu is putting out the proper 5v and it’s not being lowered by any throttle body circuitry. I’m actually hoping this fixes it, waiting on rockauto now…

 

What's the failure mode of a hall effect sensor? If it failed, would it allow the full voltage to get to the ECU?

 

I don’t think the Hall effect failed. There is really nothing to fail. I think it was a capacitor in the black housing.

 

Capacitors do fail. Over voltage is the usual failure mode as current blows through the dielectric material and causes a short, but manufacturing defects can also occur. There's really no way to test those unless one can get the circuit board out of the housing and separate the components to individually test them. I also doubt the Hall effect part of the system failed unless there was mechanical damage to the housing.

 

Agree on the hall effector not being a failure point. There are really no moving parts of it to fail, other than the butterfly flap becoming separated from the plastic gear, but that looks very unlikely, and would be very easy to detect.
Here’s how the hall effector works:

In the housing is a fixed magnet. That’s the horizontal dark line. This magnet creates a field which is sensed by the magnets on the rotating butterfly flap, thus creating a system that can make a usable signal for the ECU to interpret.


This field interacts with other magnets that are fixed on the rotating butterfly flap. As it rotates, these magnets act as a potentiometer, which changes the 5 volt reference voltage being routed back to the ECU. The ECU interprets the varying voltage as throttle angle. When the flap is closed, the ECU knows it should see about 0.8v. When the throttle is wide open, it should see about 4.5v. In my case, I see 4.8v coming back to the ECU from the reference voltage, which can only be a short in the internals of the throttle body.

Now that I think about it, when I first brought this FJ home back in August, I couldn’t get it up the driveway because it was in limp mode. I had to put the differential in 4L to get it up my slightly inclined driveway. I had 16 CELs when I brought her home. I attributed that to the suspected bad head gasket. Now I’m thinking it was this.

In the schematic is where I think I have a problem.

UPS hosed me, my part is now delayed until Monday, and I leave Sunday night for work. Will have an update next week….

Hope unpacking the internals of the throttle body helps someone someday!

 

It figures. FedEx is worse.