The Harsh 2-1 Down Shift With Lexus… It’s The ECM
Over the last two years I’ve been keeping track of this harsh 2-1 downshift complaint on Lexus model ranges from 2004 – 2006: LS430, GS300 & GS430, transmission A650E, A761E & A960E.
You might hear of this complaint; harsh down shift and a chatter on lock-up. The fluid is dark and smells and usually these vehicles have high mileage. This would have all the indications that it’s time for a rebuild.
Toyota has had ECM issues for many years, usually on specific units. But to have an ECM issue on a Lexus is pretty uncommon. My first dealing with this was a long painful road of testing and replacing of parts. The purpose of this article is to cut to the chase and save you both time and money.
This is my recollection of the first time I took on this problem. The transmission had been rebuilt, the fluid was smoked, harsh downshift, TCC chatter etc. During the rebuild they installed all new molded pistons, clutches and rebuilt converter.
After the install, resets and test drive, all of the up shifts were good and no codes were present. Unfortunately the harsh 2-1 downshift was still present. The first thing I asked was if the ECM had been reset after the rebuild?
The ECM was reset using the scan tool and the correct fluid was used for this transmission. Fluid types can be very picky when it comes to transmissions these days. They used Genuine Toyota ATF-WS. ATF-WS is NOT compatible with T-IV or Dexron ATF, in this case we have the right fluid.
The first step at this point is to check line pressure to see if we are dealing with a pressure problem. Checking the pressure in drive, it should be around 60 psi at idle. It was right at 60 psi.
We did a stall test; it was at 190 psi. In reverse at idle pressure was at 75 psi and stall was 230 psi. Line pressure was not the problem.
This transmission shifts clutch to clutch and has eight solenoids that can be a problem. Even though the valve body was vacuum tested and repaired we felt there might be some suspect there. This job needed to go, so they ordered a rebuilt valve body.
Before installing the valve body they did an air check using 25-30 psi and the air check passed so they installed the valve body and reset the ECM again. Only to find that it has the same problem.
At some point in this exercise we have to realize, there are only two things that cause comebacks and never-lefts: Parts or Technique. Simply put, either we have the wrong parts on this unit causing this problem or we are doing something wrong.
We both agree it’s NOT the transmission! We replaced and reset the ECM, and this time, IT WORKED!
Since then I’ve had several calls on the 2004 Lexus LS430 with the same problem after listening to what they have done and checked I will tell them the story I have just told you and about the ECM fixing the problem. But even though ECM failure is common on these vehicles you still want to follow the right steps before simply replacing it.
Here’s some added value:
In 2013 Lexus came out with a bulletin on replacing the ECM to fix the harsh 2-1 down shift. At the price of around $2,000 plus labor to install. HARSH 2-1 DOWNSHIFT WHEN COMING TO A STOP
Bulletin# L-SB-0126-12 Rev1 Superceded Bulletin(s): L-SB-0126-12, Date of Issue: December 04, 2012
For those of you that are out of any type of warranty I have found a source for computer repair I have had good feedback on repairs that have been done the repair cost has been about $275.
And like I tell everyone if you are happy with their work tell a friend if not tell me, this is their web site WWW.DIGITALAUTOTECH.COM located in riverside CA. and that’s not just smart.
THAT’S STREET SMART!
