Overdrive Wiring for standard Lexus Auto Gearbox

[Tonyd]

Guys,

Just got one last wire to connect before sending the first 1UZFE powered Lexus Cobra in the UK to the trimmers.

I need to finalise which wire I send 12v down into the ECU to switch overdrive on and off.

I have a four connector ECU and loom with 28/16/22/34 pin from a 1993 LS400 and looking at the wiring diagrams from this site and others, although none give a definitive answer I can see, I tend to think that pin 6 ( blue and yellow wire) in the 28 pin plug is the one to connect to the overdrive switch to send 12v down when I want o/d.

Obviously I dont want to risk frying the ECU so can anyone confirm my thoughts or give me a definitive answer re the correct pin for the overdrive signal?

cheers,

Tony

 

[mshawari1]

Find the OD pin and connect it to ground "-ve"​

 

[Tonyd]

Find the OD pin and connect it to ground "-ve"​

And the number of the OD pin is?

Cheers,

Tony

 

[Tonyd]

And the number of the OD pin is?

Cheers,

Tony

I'm going boggle eyed at these wiring diagrams here but please correct me if I'm wrong.

Putting power down the blue yellow wire into pin 6 of the ecu tells the ecu to engage overdrive when condition allow.

Then when you switch the power from the ecu to the overdrive off light ( by using the o/d switch) the ecu then prevents overdrive being engaged.

Earthing the OD pin would render Overdrive permanently disengaged, whilst putting power down the OD pin would mean OD would be pernmanently engaged when appropriate.

In my diagrams theres only two OD wires, one is blue yellow and goes to the OD switch and light and the other is violet red and goes to the Cruise control ECU.

As I see it theres only the one option ( blue yellow) , but I'd hate to buggar it all up now.

Cheers,

Tony

 

[madmont]

I would be earthing the blue/yellow wire to tell it not to go into overdrive. Earthing this wire turns on the "OD OFF" light which is also your malfunction light.

 

[devojet]

This Document might help.

http://www.autoshop101.com/forms/h16.pdf

 

[Tonyd]

This Document might help.

http://www.autoshop101.com/forms/h16.pdfhttp://www.autoshop101.com/forms/h16.pdfhttp://www.autoshop101.com/forms/h16.pdf

Thanks Devojet the very useful document confirmed exactly what I was thinking. It is the clearest explanation of how the ECT works I've yet seen. My mind is now at peace and I'll finish the wiring and get the car into the trimmers.

Le Mans Classsic here we come !!


Cheers,

Tony:slomo:

 

[devojet]

Yeah it's a good document, I can't count how many times I have read it. There are more good toyota documents on that web site as well.

cheers

Daniel.