Toyota RAV4 ECU Re-Installation & Troubleshooting Guide

Here are two simple procedures that will help you eliminate the cause of the problems that may occur when installing the ECU back into the vehicle. (01-03 Rav4, Picnic, Avensis. 4x4 – AWD & 4x2 – FWD)

Procedure 1:

There is a common issue with the connections on these models when reinstalled. The 5 white plugs that connect to the ECM are so tightly cut in length that these connectors tend to be too stretched when engaged and end up disconnecting partially from the ECM terminals even when the plastic part is still in place and looks well and engaged.

Please make sure that all 5 connectors snap all the way in and also check that there are no wires backing up while you push the connectors in. Any single wire in any of the five connectors that backs up while any of the plugs are pushed in, will turn into an incomplete or intermittent connection. If that is the case, you may push that single wire or multiple wires to its place with a pin or any other pointed object.

Also, make sure that there is no foreign material between any of the connectors and the terminals in the ECM they go connected. Dust or metallic debris, will either cause a poor connection or a short between one or more wires in that area.

Finally, make sure that wires are not too stretched. Try to use the same path the wires had when installed from the factory. Otherwise, vibration from the vehicle will induce connection problems to the ECM in the long run.

Symptoms:

If the above happens, the vehicle will either have the same or similar symptoms as when the ECM was failing.

Procedure 2:

Your ECM was reprogrammed to go to relearn mode as soon as installed, which is an automatic process where the ECM attempts to relearn the proper shifting codes from the transmission in your vehicle while in use.

Many vehicles work flawlessly as soon as a new or repaired ECM is installed; however, there are some others that will need to go through a longer relearn process to adapt to mechanical changes in the transmission. These mechanical changes are induced when the transmission suffers some wear while it is used with a failing ECM. If this is the case, all symptoms should have gone away, except for some hesitation when shifting to third gear.

The relearn process should not take more than 15 minutes of driving the vehicle in normal cases, but it may last even up to a week in rare cases. The more the transmission wear, the more time it will take to complete this process. A relearn process that takes more than a day to finish, it will mean that the transmission has considerable wear.

Please note that for the process to end, the vehicle should be driven normally. If it is turned on while parked, no changes will occur, as the transmission is not shifting while parked.

Symptoms:

All symptoms should have gone, except the hesitation while shifting into third gear