RAV4 trans problem ECM or not... - Page 1
Forum section: electronics / general

author: manicdoc
author_rank: Unknown
timestamp: February 18, 2024, 10:35:41 pm
content: Hi,I've got a Rav4 2003 that's playing up after 30 minutes running on shifting from 1st to 2nd - rev ups and no power transfer... Now a trans mechanic reckons its the ECM mis driving the solenoids and getting the trans in a bad state... Thing is there is a known fault with 2003 Rav4 ecms, but I had the ECM out and its not the version impacted (which had one single power sense resistor per solenoid, mine has two in parallel) - for good measure I reflowed the resistors and everything measured in spec. We changed the trans fluid that was dark red (hadn't been changed since new I reckon) and a local mechanic changed the trans oil filter. Now the problem occurs shifting 2nd to 3rd.. Also no codes generated throughout.Just wondering if anybody else with Rav4 ECM experience has come across this and if there is an easy way to determine the core problem. BTW putting the shift into '2' and the problem goes away. Just wondering if with the change of oil it needs to adjust.Any help appreciated.

author: darkspr1te
author_rank: Frequent Contributor
timestamp: February 19, 2024, 06:44:06 am
content: Hi,Which auto box do you have ? Is a CVT series ? (k111-k114) these models require regular fluid change and a re-learn procedure after that is done.For the pre ctv boxes you can use the toyota OBD diagnostics software (techstream) to view the solenoid states and what the computer is telling them to do, or if you a have a good enough scanner that can show the same.if you just did a service and as a result you have new symptoms then you are on the right track. I had a auto rav4 on pre ctv that never in it's life had a fluid change, we did the first one and i had symptoms to yours (shifting changed) and toyota tech told me to do it again as draining the pan only removes about half the actual fluid and the rest is stored in valves and the primary pump and that needs clean fluid too. I can confirm this is most definatly the case on CVT base units as the manual actually specifies two fluid changes (first is drain and fill with toyota "atf cleaner" , warm up and short drive then drain and refill with final fluid, this is also mentioned in techstream software)I am doubting the ecm at fault here as the fluid change also changed the symptoms so it will more be old fluid in the system still or actual solenoids have stuck due to contaminatesdarkspr1te

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 19, 2024, 01:17:29 pm
content: Definitely wouldn't be a CVT since a CVT doesn't shift gears. Most likely the next thing to look at is the control valve assembly, hopefully it would be a simple fix. If there's problems in the main mechanicals, it probably wouldn't be worth fixing for such an old car.Here are a lot of videos on transmission troubleshooting:https://www.youtube.com/@AutomaticTransmission/videos

author: amyk
author_rank: Super Contributor
timestamp: February 20, 2024, 04:49:56 am
content: Look for "ATSG U140/U240" - I believe this is the service manual for the one used in your vehicle. It doesn't have hydraulic schematics but does have the electric ones, so you could add some test leads and a multimeter to check whether the appropriate solenoids are being driven by the ECM as it shifts:https://gearsmagazine.com/wp-content/uploads/2017/05/fig2-4.pngThe page that's from may also be useful:https://gearsmagazine.com/magazine/correcting-toyota-u140u240-shift-troubles/If manual 2nd works but auto 2nd doesn't, then it's not the geartrain or clutches that's the problem.