I hope someone can help me problem solve my 2003 rav4 issues. Recently, my rav4 has been slipping from gears 2-3. After exhaustive research, I found out that my car is known to have a bad ecm. So I decided to get a fixed ecm and replace it in my car. Car still slips so, thinking the ecm is good, I had my transmission rebuilt. After rebuilding my transmission, it still slips from gears 2-3. Do I need to replace my ecm again to coincide with the new transmission? I’m completely at a lost.
We do not have enough info. How many miles on the trans and what was the service history. Was the ECM codes read before rebuilding the trans.
At this point it seems like random & costly repairs are done without a good diagnosis.
Is this an automatic transmission or manual? What do you mean by “slips from 2-3” ? You put it into 2, and it goes to 3 after a while? Or it is 2 or 3, and it slips by itself into neutral? Or in 2 and 3 and you press on the gas it seems like the engine speeds up but the car doesn’t, like the transmission is slipping? Suggest to explain a little more the symptoms.
A good write-up on common issues with this transmission:
http://www.sonnax.com/articles/126-Toyota-U140-U240-Series-Diagnostic-Information
It’s an automatic…so when it’s on 2nd and tries to go to third it feels like its on neutral for a split second and then kicks into third…so for a split second when I’m stepping on the gas the car doesn’t accelerate, then it jolts forward.
Thanks for the link @ insightful. I’m assuming that since the transmission just got rebuilt, the potentisl issues stated in the link shouldn’t be relevant to me?
@Galant…the car has 130k miles on it. The check engine light did not come up but the car was definitely driving very off and I just mentioned how the car was driving.
That is low miles for a Toyota Transmission, but if it saw a lot of stop and go or lack of maintenance, then it could happen. I think you need to go to a transmission specialist, different than what you have used and have them start the troubleshooting all over again. I believe that the transmission codes do not necessarily trigger an engine light and need a high end code reader to get to.
Thank you @galant. It is very low mileage for a Toyota transmission but 2001-2003 rav4 are known for having a faulty ecm that damages the transmission. I did take it to a transmission specialist but to no avail. 
I was hoping someone had dealt with something similar to my situation and had a solution for me. I’ll go back and see if the transmission guy has a high end code reader.
I'm assuming that since the transmission just got rebuilt, the potentisl issues stated in the link shouldn't be relevant to me?
That depends on the quality of the rebuild.
Did you go to the transmission specialist and tell him “I’m paying you to diagnose and repair my problem”
Or . . .
Did you go to the transmission specialist and tell him “I’m not paying you for diagnosis. I’m paying you to rebuild my transmission”
As for that ecm and the information you read . . . since you’re not a mechanic, I advise against throwing expensive parts at a car, just because you read something and some guys said something
What may be worthwhile . . . pay a Toyota dealer to check if your module has the latest software level. And if not, pay them to upload the latest software. Toyota has had some bulletins concerning shifting, and the repair has been updated software. Not sure if it applies to your vehicle, though
U paid a shop to rebuild the trans due to a poor 2-3 shift. U told shop about issue. They rebuilt trans and have warranty? U did talk to shop and discuss issue? Seems a renamed different trans might have been better route. Same r&r process and not much more money. Too late now.
Ok, I understand, the transmission seems to be slipping during the transition from 2 to 3. Here’s the thing: Automatic transmissions have clutches in them just like manuals. Little gadgets with friction surfaces on them. It’s just that with auto trans there more of them, and each one is smaller. And a frequent symptom is the friction surface wears out, and start to slip, producing this symptom.
Most likely possibilities
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The clutches are worn out, possibly they were not replaced (as would be expected) as part of the prior rebuild for some reason.
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In days of yesteryear auto trans were purely mechanical contraptions. Sort of mechanical computers in a way, operated by vacuum, fluid pressure, and centrifugal forces. But this transmission of yours is fairly new and is probably electronically controlled with a number solenoids. If one of those solenoids is on the fritz, this symptom is possible.
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The transmission fluid pressure is one of the forces used to keep the clutches from slipping. With newer trannys like yours, there’s a computer that monitors for slipping and this fluid pressure and will boost it up higher if it notices slipping occurring. But that will only work for so long, after which it can no longer provide enough boost to prevent slipping. That can happen if there’s an unwanted internal leak inside the transmission. It won’t leak onto the ground, but it won’t be able to boost the pressure high enough to prevent slipping. That’s what the rebuild was supposed to prevent, but maybe something went wrong. A shop has tools to measure the transmission fluid pressure to say Yes or No to this idea straight away.
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Modern automatics require a very specific transmission fluid, and each manufacturer seems to have their own. It’s a good idea to use the manufacturer’s fluid. The other thing about modern trannys, they are very sensitive to fluid level. Even a little off, high or low, can cause this symptom. And checking the level isn’t an easy thing to do these days. The vehicle has to be perfectly level, the fluid at the correct temperature, and often there’s a routine that has to be done that requires the use of a special manufacturer-specific scan tool.