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2005 LS430 Downshifts from 2 to 1st too early, causing jerk/jolt/clunk/.
Lexus dealer diagnosed that the problem is ECM and quoted me $2272 ($1800 parts + labor + tax). It seems little expansive to me. They said there are no TSB to fix this issue for 2005 model.
Has anybody send out their ECM/ECU for repair to some shop listed online and was it successful?
Can you buy a ECM from ebay and reprogram it yourself or can only be done by the Lexus dealer?
Any help would be greatly appreciated
Thanks
Very weird that Lexus dealer made such a huge discrepancy in their final word which cost you a lot of money. While I still trust Lexus dealers in doing proper diagnostics because they have tools approved by Lexus, I should say that they need to double check you newly repaired ECM for any transmission-generated codes if any exist.
From my perspective, Your transmission problem looks like there is a problem in valve body. I suggest a highly qualified technician who knows Japanese cars to look at this element.
Fortunately, Ebay sells pre-owned valvebodies in case if you confirm the problem is there. Also, I suggest to replace sensors there only if you see the code or the resistance is going out of normal.
Here is a copy of TC006-04, just in case if you don't have it readily available...
Thanks rkw77080 for the info, if i am reading this TSB correctly
2005 model year LS 430 vehicles produced BEFORE the Production Change Effective VIN shown: JTHBN36F*5005700
and my vin is : JTHBN36F655011259 then this TC does not apply to my car. is this correct?
I don't believe the transmission speed sensors caused the harsh shifting from 2nd to 1st. However, if you want to remove, clean, and reinstall these sensors, here are the details (location, torque specs, etc.) for your reference...
What do you use to clean these sensors. Same stuff you use for MAF sensor?
I can measure the resistance with an volt meter.; correct?
you said "don't believe the transmission speed sensors caused the harsh shifting from 2nd to 1st."
So I am desperately trying to understand how the transmission decide to down-shift or up-shift. I would have thought that this is decided by the some speed sensor on the engine. which might be the front sensor on the Transmission. Sorry I don't have the knowledge I am just guessing.
Also wondering if the error codes are cleared using a OBDII, can you retrieve them back or not or do I need to drive few hundred miles before they show up again?
Thanks rkw77080 for the info, if i am reading this TSB correctly
2005 model year LS 430 vehicles produced BEFORE the Production Change Effective VIN shown: JTHBN36F*5005700
and my vin is : JTHBN36F655011259 then this TC does mot apply to my car. is this correct?
Confirmed. Your VIN is after the cut-off VIN JTHBN36F*5005700 and therefore this TSB does not apply to your car.
Very weird that Lexus dealer made such a huge discrepancy in their final word which cost you a lot of money. While I still trust Lexus dealers in doing proper diagnostics because they have tools approved by Lexus, I should say that they need to double check you newly repaired ECM for any transmission-generated codes if any exist.
From my perspective, Your transmission problem looks like there is a problem in valve body. I suggest a highly qualified technician who knows Japanese cars to look at this element.
Fortunately, Ebay sells pre-owned valvebodies in case if you confirm the problem is there. Also, I suggest to replace sensors there only if you see the code or the resistance is going out of normal.
one of these :
LS430 Automatic Transmission Valve Body W/ Harness
The A761 Trans is EXTREMELY sensitive to incorrect fluid levels. Now that you know it's not the ECU, aka expensive potential fix, i would revert back to cheap and simple. Start with a basic drain and fill, which involves replacing 2 to 3 quarts, and replace with Toyota WS. The critical thing here is getting the new fluid level correct. It can be tricky, as your car does not utilize a trans dipstick, so it might be in your best interest to pay a professional to do the job. Your local Toyota dealer has the proper tools and I'd hope they won't try to sell you a new ECU like Lexus did?!?
Also VERY important- keep the drain and fill simple with just a few quarts. The main goal here is achieving a proper fluid level. Don't do all the fluid at once and definitely don't do any type of power flushing service. Hope this helps and keep us updated on the results.
Thanks for this very valuable info - When I take it to the Toyota dealer do I tell them to do only "drain and refill" and not a power flush? Drain only part of the old fluid and not all of it??
Approximately how much should this cost?
Simply draining what is in the pan is only a few quarts. The majority of the fluid is trapped in the torque converter and cooling lines during this process. Again the main objective is achieving a proper fluid level but it won't hurt to get a little fresh fluid in there during the process. Stay away from any service that uses pressure to remove the old and replace the new aka a "flush". Depending where you go it should be under $100...
What do you use to clean these sensors. Same stuff you use for MAF sensor?
I can measure the resistance with an volt meter.; correct?
you said "don't believe the transmission speed sensors caused the harsh shifting from 2nd to 1st."
So I am desperately trying to understand how the transmission decide to down-shift or up-shift. I would have thought that this is decided by the some speed sensor on the engine. which might be the front sensor on the Transmission. Sorry I don't have the knowledge I am just guessing.
Also wondering if the error codes are cleared using a OBDII, can you retrieve them back or not or do I need to drive few hundred miles before they show up again?
You are correct, the ECM uses these speed sensors to control transmission gear shifting. Your car will throw a P0717 DTC if the NT (transmission input) speed sensor is bad, within seconds of driving. Likewise, it will give you P0500 if the SP2 (transmission output) speed sensor is bad. These DTCs will also activate the MIL (Malfunction Indicator Light) on your instrument cluster.
Thanks for posting image of valve body with wire harness...
Not a fan of single wire to critical components such as valve body solenoids...too dependent on integrety of engine grounds. Reminds me of early General Motors single wire oxygen sensors that relied on the exhaust sytsem for the negative ground path..
Check your negative battery cables and all negative grounds..
Also, cropped the original image of harness where I believe transmission temperature sensor is located..
If a resistive element, then probably past its prime...
The receipt from SIA Electronics says "Rebuilt transmission circuitry"
Each ECU has 2 types of memories - ROM (Read-Only memory) and RAM (Random-Access memory).
ROM is non-volatile and its contents are retained even after the power is switched off. All the default settings and control algorithm of the ECU are store in the ROM. Vehicle identification info is also stored there.
RAM is referred to as volatile memory and is lost when the power is turned off. Your car keeps track of your operation habits in the RAM to try to optimize the car's performance. Sometimes the data stored in the RAM can "confuse" the ECU, and one way to un-learn what is stored in the RAM is to disconnect your battery's negative cable to wipe clean the RAM.
As long as the ROM was not altered, your repaired ECM should still remember its identities. Sorry for the long winded reply - the short answer is: I think you're OK!
Thanks rkw7708 , great write up . Finally it makes sense to me when people say disconnect the battery to reset the ECU.
Today I spoke to a Master Toyota Technician and he said he would do a total flush of the Transmission but from a Lexus or a Toyota dealer to make sure it is done correctly. Then I spoke with a Transmission expert and he said no he would only do drain and refill.
02-10-18, 07:41 PM
