Hey guys I’m really trying to figure out what’s wrong with my car, it’s a 2004 Lexus LS430 with 160k miles. It started the other day when I’m slowing down under 10mph it will just slam the car into first gear before it’s at a complete stop but very harshly and you somewhat feel 3-2 hard shift as well but 2-1 is very violent and jerky. I do not believe it is the transmission because I’ve had other cars with transmission issues and you’ll start feeling signs of slipping or other issues before it gets bad but my Lexus was good one day and acting up the next day. Please let me know if anyone has had this issue and what is the fix for it. I just took it to a shop and they said it was the transmission and 3k to fix but you know how shops are. Also there is no error codes or check engine lights and the car accelerates fine it just acts up when it’s time to downshift.

 

Pretty common, unfortunately. And you’re right, it’s not the trans. Further reading: Start here

 

Ecu problem. Needs a new ecu or send yours out for repair. I read sia electronics can fix this problem.

 

After trying to figure out what was wrong my local Lexus mechanic mentioned he had replaced another customer’s tranny w/same problem and it DIDNT fix it. Ordered a used ECU(81 not 80) and transmission ran normally after installed. Took to Lexus dealer for 2nd opinion and they recommended a new transmission for $5K. Said no thanks and had my local guy pull the ECU and I shipped it to SIA in Chicago. SIA said this was a common problem with this ECU and they would rebuild the transmission portion of the unit and mail back. Took about 10 days but got ECU back, installed and car runs like new. SIA charged me $135 for the whole repair. I guess the Lexus dealer was going to put in a new transmission and when it didn’t fix the problem tell me I needed a new ECU. For $2k. Don’t know if they are just idiots or trying to stick it to me but they definitely have a credibility disconnect with me. Anyway SAI fixed the issue and saved me a ton of cash.

 

try this before you spend any money. Worked for me and others and totally free

https://www.clublexus.com/forums/sc4...t-the-ecu.html

 

Are the ECUs problematic for the 04-06 LS430s with regards to the transmissions?

 

Had identical problem w/ slow speed 2>1 abrupt downshift. Had the ECU reset. Changed the ATF 3x. End of problem. Also upshifts very smoothly (even under full acceleration).

 

+1 on SIA...pleasure doing business with them and solved the issue. Was happy to give them my money when the dealership wanted to replace transmission.

 

i went in to lexus and they had a update for the ecm they tried to charge me 4 hours of labor so i left not worth

 

This is really sad when dealers basically defraud customer’s wallets to do some simple stuff like connecting mongoose cable and setting up quick ECM flashing which lasts maximum of 10 minutes... but the iceberg of the “fraud” scheme is replacing expensive computers instead of organizing normal repair service inside dealership facility.

 

I did this and nothing, once I remove the key do I have to wait again or can I just put the key back in and turn it on?

 

where is the ECU and is it easy to remove? And what’s the turn around time for SIA is it the location in Illinois?

 

The ECU is just behind the driver's side headlight. Just a few clips and 10mm bolts and then a few wires. Took me all of 10 minutes with no knowledge of anything under the hood.

 

I sent the unit out on Saturday and had it back by Wednesday. It is the location in Illinois. I am located in Chicago so that might have expedited things, but they still had it sent out same day they received it, so I would say having it back in a week is within reason, regardless of where you are located.

 

I was able to take on my ECUand did a visual inspection and it seems fine no leaking capicitors like others mentioned so I’m still hesitant to send it to SIA what if it’s not the computer :/