Installed a low mileage transmission on my 2004 lx 470 it won’t go into 1st and 2nd gear. Bad ECU? (1 Viewer)

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Not sure why you did not report P0771 in OP, or when I asked.
****P0771 came up 1 time. Once cleared, it never came on again.


I do recall a few reports of what "mud guys believed a defect", in the early 343 (98-02) IIRC pre May 2000 MFD. The biggest issue with the 750 (03-07). Was under filled from the factory. It was also believed a vent tube was allowing water in. But that may have been low fluid also.

I'll assume this is the donner transmission. A server wreck can cause damage to moving parts, dislodge connecting, etc. even those not directly impact. Was transmission pan pulled and inspection done?
**** Pan was not pulled or inspected in order not to void warranty.

Since you also said Dealership topped the transmission. BTW: This is no guarantee done correctly. Can we also assume you did not do the install yourself?
****Dealer topped off at proper temperature.

Are you doing the diagnostic or taking to someone?
****Dealer doing diagnostics.

Any other issues codes with your vehicle, any?
**** No other codes
 
Joined
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We also clear codes then see if returns. Since code didn't return, I'd only keep as footnote. Very likely during install or some service the code was tripped. Let us know what your Lexus Dealer reports.
 
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Check the speed sensor connections and check the sensors for damage. Link below is FJ Cruiser-specific, but it shows the logic the ECU uses. Since this page below seems to suggest that current data is getting compared to stored values, a reset of the ECM memory is also advised. Disconnecting the battery won't do that, it needs to be cleared with Techstream or by the dealership.

You could have some crud stuck in the SR shift solenoid, but you have to drop the pan to check and test it. I had an 2001 Ford Ranger once that would buck like a bronco at idle from a gummed up shift solenoid. Then one day, it just magically went away as whatever crud was in there worked its way out. I took that as a sign to trade it in (on a 2005 Titan, what a mistake that was!!!).

 
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Since we both seem to be having a similar issue. Use this link for the FSM for our MY trucks. http://www.dustbird.com/ih8mud/FSM/Diagnostics.pdf CTRL + F for P0771. We have the a750F trans.

Also you should try the manual shift test. disconnect the wireharness on the outside of the transmission. You can shift using the shifter. This will tell you if the problem is mechanical or electrical
 
Joined
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Since we both seem to be having a similar issue. Use this link for the FSM for our MY trucks. http://www.dustbird.com/ih8mud/FSM/Diagnostics.pdf CTRL + F for P0771. We have the a750F trans.

Also you should try the manual shift test. disconnect the wireharness on the outside of the transmission. You can shift using the shifter. This will tell you if the problem is mechanical or electrical
Never thought about that. Makes sense!
 
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I decided on changing the transmission yet again since the Lexus mechanics tested all the wiring and it was giving the proper readings so they thought it had to be mechanical . After installing the 3rd transmission it is having the same exact issue. This is driving everyone crazy!!!!!!!
 
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Marquette, MI
The plot thickens.....can't wait to hear more.

Reminds me of an issue I had with my 335d after a motor swap a few months ago. Long story short....some contact cleaner and compressed air eliminated the issue. Was very close to buying a DDE module and going through all the programming nightmare.
 

ramangain

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It is not easy for this community to process and provide feedback on things like "the Lexus tech tested all of the wiring and the signals were fine". What did they test, how did they test it, etc. is extremely useful.

if you can get a detailed work order report and post it, that would help us help you a lot.
 

Eicca

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Has anyone checked ground point EC on the back of the block by the firewall, passenger side? I know from experience that a loose bolt on that sucker will freak a transmission out real good.
 

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