Rav4 ECU/ECM/Transmission Problem Recap

Some months ago, our 2001 Toyota Rav4 (2WD, automatic) had a problem where, late one night in Tampa, it started from a light extremely slow. Turns out it was in third gear and this was a common problem with 2001-2003 Rav4s. The computers frequently go bad and send bad signals to the transmission.

I didn’t find this out until the transmission rebuild was already done, which was unfortunate. Maybe the transmission wasn’t yet dead as my wife pulled over as soon as possible and we had the car towed.

We had someone in Minnesota repair the computer for $69 over the long Christmas weekend. He said they had trouble with the computer but didn’t provide any details and eventually told us it was done.

After rebuilding the transmission and getting the computer repaired at the same time, the car wasn’t the same. Power would drop out if you took your foot off the gas, it just seemed strained and its top highway speed was reduced. And if you went to pass someone starting from 60mph on the highway, there was just no power anymore.

There was a persistent Check Engine light even before the computer/transmission problem came to our attention. We were assured it was an outgoing O2 sensor (P330, I believe) and that it wouldn’t impact the car’s performance in any way. So we didn’t fix it right away.

Last week I spoke to Sergei, another person who fixes these computers (eBay ID: chkengine) and we discussed that the power problems might be the computer or they might be the mass air flow sensor (MAFS) or something else. Then, on Friday, I spoke to his tech, Vladmir, and he suggested we start from a known-good computer before we try to debug it further. So I bought a repaired-by-them ECU for $300, which included Express shipping. USPS delivered it this past Saturday. Nice. These guys so far have just been very helpful and, for whatever reason, I have confidence in their Rav4 ECU repairs.

Today my mechanic was unable to get a code off the car with the old ECU installed. That’s a new symptom. I gave him the go-ahead to install the new ECU anyway. They installed it and the old code (O2 sensor) was gone, replaced by a new code, P1135, bad fuel/air mixture sensor heater.

We’ll drive it a few days and see if the O2 sensor fault code recurs. I’ll pull codes each night when I get home to see if there is any change.

And I’ll look into that P1135 code. Maybe it’s the MAFS after all and it just needs to be cleaned, which I’ve seen reference to on the internet since first talking to Sergei last Wednesday.