ECU question - can it turn voltage off? (LS460)

[OJWM]

Asking this question to make myself feel better / more optimistic...!

In an earlier thread, I had asked some questions relating to coolant issues. In the end, it turned out my LS460 needed a new water pump (and also suffered the infamous broken radiator connector in the process... meaning I got that replaced too).

To add some insult to injury (the above work being complete and 'successful'), car now has an unsteady idle, a dashboard lit up like the proverbial Christmas Tree, is in limp mode and has thrown codes relating to TPS sensor circuit (P0121 and PO123).

Mechanic attempted to solve, but couldn't. He did discover a wire within the throttle body connector had come unstuck. He seemed to almost discount that wire as a cause when he found that no voltage was going to connector's power wires...

Having thought on it, I think (and hope) that the below might fix issue:

• Rewire loose wire
• Disconnect Battery for 20 mins / pull ECU fuse to reset it
• Restart car + cross fingers

Does anyone know though (just so I can adjust level of optimism accordingly) - can the ECU decide to turn off power to certain wiring looms if it is suitably upset (as presumably it would have been in this instance)?

 

 

[ambermarine]

I find it extraordinary that a so called mechanic can find a wire in the throttle body that was connected to something and diregsrd it as irrelevant.These cars are electronic minefields and the designers at Lexus do not leave anything to chance ,so a loose wire as been doing a job they are not put in for decoration.

Take it to a  qualified up to the mark technician before you end up with a absoloute morass of pain and anguish.

[OJWM]

48 minutes ago, ambermarine said:

I find it extraordinary that a so called mechanic can find a wire in the throttle body that was connected to something and diregsrd it as irrelevant.These cars are electronic minefields and the designers at Lexus do not leave anything to chance ,so a loose wire as been doing a job they are not put in for decoration.

Take it to a  qualified up to the mark technician before you end up with a absoloute morass of pain and anguish.

I was probably wrong to say he discounted it. When he found it, he was confident it was the issue but lost that confidence when he couldn't find any voltage going to the wire. I suspect that was because ECU shut that relay down when it first found wire wasn't connected.

 

 

[steve2006]

Seems a bit strange that the guy couldn’t “find any voltage going to the wire”

Bit too much of a coincidence that before the work was carried out all was well electrically/electronically but since then a wire has broken causing a fault don’t you think?

There are basically three types of wire, supply voltage (12/5 volts)ground and signal the latter 2 having no discernible voltage present one being at ground so 0 volts and the other carrying either a specific waveform signal only viewable on an oscilloscope or a variable voltage.

If you want to see great examples of proper vehicle fault diagnosis take a look at “Diagnose Dan” on YouTube.

[OJWM]

Turns out that the obvious issue was the fix and that, indeed, Lexus don't design spare wires into their throttle connectors 😉

I reseated detached wire today (with Battery disconnected obv). On turning car back on, no code, stable throttle. Relief...

[steve2006]

And the mechanic?