SC430 - 2nd Gen (2001-2010)

ECU or Transmission

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Old 09-06-18, 09:06 PM
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Giddyup08
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Default ECU or Transmission

I had posted a thread a few months ago regarding my 2006 SC430 (79,645 miles). When I slow down, the car is thrown into 1st gear (causing me whiplash half the time). I can tell that it doesn't shift right when reaching 40mph. There's like a delay. I took it to the dealer and they said it was either the engine computer or the transmission. They gave me a price of $3000 (ECU) or $7000 (transmission). I got some great advice from some of the posters here, thank you for steering me in the right direction.

I ended up taking it to a local transmission shop. It sat there for over a month. They said the same thing, ecu or transmission. No help whatsoever. I ended up with a dead battery that I had to replace. If you have a trusted mechanic, be very thankful!

I decided to replace the ECU myself. I found one online to match my computer number exactly. I contacted a locksmith for all the re-programming. This morning he came and did what he had to do. Total cost $357 (part and labor). I couldn't wait for him to leave to test the car out. I drove it around the subdivision and to my surprise my problem was solved....so I thought.

I was all excited driving to work. And then it happened. I was approaching a red light and boom....jolted and thrown into 1st gear.

So, at this point, I'm thinking that I never made it out of 2nd gear when riding around the subdivision. I made it into at least 4th gear on the way to work. Any thoughts? I was going to try replacing the solenoid next. I've gotten a price of $700. But will still call around.

I called the dealer for the heck of it and talked to one of the guys from service. He was quite nice and said the odds of it being the transmission was slim. He looked it up and said that since 2013, they had 5 transmissions replaced.

As a reach, I'm going to disconnect my battery for 10 minutes and say a quick prayer. I'm not optimistic though.

Thank you in advance!
Old 09-07-18, 03:22 AM
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Bgw70
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https://www.clublexus.com/forums/sc4...nsmission.html

here is your old thread...it provides the rest of the story.
BTW, it was easy to find, I just clicked on your name and clicked, “find more post by this person”

so, did you ever change the fluid?
Toyota and especially Honda like clean fluid...
Old 09-07-18, 06:55 AM
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Caflashbob
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Back flush the trans.
Old 09-07-18, 01:55 PM
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Coleroad
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Were they talking the transmission ecu or the main ecm? That's crazy the kept the car that long, and to only give a guess. Sorry you were treated like that.
Old 09-08-18, 06:55 AM
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sixonemale
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Originally Posted by Giddyup08
So, at this point, I'm thinking that I never made it out of 2nd gear when riding around the subdivision. I made it into at least 4th gear on the way to work. Any thoughts? I was going to try replacing the solenoid next. I've gotten a price of $700. But will still call around.
If disconnecting your battery was unsuccessful, I believe you may be on the right track going after the solenoid. I once had a transmission rebuilt on another vehicle with an aftermarket solenoid and about a year after the rebuild it began to make harsh shifting adjustments similar to what you have described. My only advice is that if you do replace the solenoid go with OEM and not an aftermarket solenoid.
Old 09-08-18, 08:02 AM
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DshngDaryl
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Have you checked your motor mounts? As silly as it sounds, MANY people report serious transmission problems, only to find out it was their motor mounts.

Here is just one example: https://www.clublexus.com/forums/sc4...problem-2.html
Old 09-08-18, 09:50 AM
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Bgw70
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What causes the P0756 code?

There are a number of causes that could be behind this code appearing. They are:
  • Hydraulic blockages occurring inside the fluid passages of the internal transmission
  • Low amounts of transmission fluid
  • Failures having to do with the mechanical aspects of the internal transmission
  • Dirty transmission fluid It’s also worth pointing out that the actual computers could be wrong. The PCM or the vehicle’s transmission control module could both be at fault, though this tends to be pretty rare.
Again, I would start with the transmission fluid.
Has it ever been changed?
if yes, did they use the wrong type?
if not, Change it! it’s not difficult and it may correct the problem.
the 2006 and above have a different procedure and a different way to check the fluid level. It’s still easy, just different.

BTW, how much have you spent so far?
Old 09-08-18, 10:36 AM
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sixonemale
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Originally Posted by Bgw70

What causes the P0756 code?

There are a number of causes that could be behind this code appearing. They are:
  • Hydraulic blockages occurring inside the fluid passages of the internal transmission
  • Low amounts of transmission fluid
  • Failures having to do with the mechanical aspects of the internal transmission
  • Dirty transmission fluid It’s also worth pointing out that the actual computers could be wrong. The PCM or the vehicle’s transmission control module could both be at fault, though this tends to be pretty rare.
Again, I would start with the transmission fluid.
Has it ever been changed?
if yes, did they use the wrong type?
if not, Change it! it’s not difficult and it may correct the problem.
the 2006 and above have a different procedure and a different way to check the fluid level. It’s still easy, just different.

BTW, how much have you spent so far?
Good thoughts. It's always best to begin with the least expensive repair and work your up to more costly repairs if necessary.
Old 09-10-18, 08:43 PM
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k7q
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I would say ecu. LS430 & 06+ GS has this problem. I seen some on the LS page send their ecu out to SIA electronics to get rebuilt.
Old 09-11-18, 04:40 AM
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Goldwinger
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As you mentioned in your other post you had a shift solenoid code. Its time to follow the proper repair steps and you might find the solenoid needs to be replaced.
They do get dirty. As the trans wear the particles stick to the magnets in the solenoids and BANG they can't work
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