[Rebbers332]

This light just came on today. What does this mean?

 

[Skinny guy]

This light just came on today. What does this mean?
View attachment 205975

Did you use air conditioner?
If so than most likely your coolant bypass valve failed.

 

[Tazio Nuvolari]

The "Engine Maintenance Required" is a special message to dread. It IS the coolant bypass valve. Search this forum and you will unfortunately find several long, detailed and angry threads about it. It is a $600-$1K dealer repair. You CAN do it yourself if you are an experienced amateur. It is do-able but no one has ever said it is a fun job.

 

[Rebbers332]

No i didn’t use it yesterday because it was kind of a cool day. And my radiator fluid is full, it wasn’t over heating and everything was working normally. I only turned on air conditioning full blast to show my brother in law when I asked him if he knew what was wrong. And then when I used my vehicle about 6 hours later that message was gone and never came back on again. Could it be my battery?

 

[Skinny guy]

And then when I used my vehicle about 6 hours later that message was gone and never came back on again.

One of mine friends has similar issue. His coolant level is OK, warning message was gone last fall and he drove his RAV4 all winter without problem till he switched on AC.
So it is easy to verify the problem playing with AC switch. Or use good bidirectional scanner for trouble codes.

 

[Tazio Nuvolari]

. Could it be my battery?

No-not the battery. The coolant bypass valve is a well known issue. Yours is toast. the same valve fails on Camrys and Corollas. Literally thousands of posts on this forum, Toyota Nation and Reddit Rav4 Club. Several YouTube videos.

 

[Tazio Nuvolari]

No i didn’t use it yesterday because it was kind of a cool day. And my radiator fluid is full, it wasn’t over heating and everything was working normally.

The valve just fails randomly at different mileages in posters' cars--can be as little as 20K miles. There are some who claim their valves have never failed at over 100k miles. Nothing you did broke that valve...they are just defective in design and manufacture.

I only turned on air conditioning full blast

The warning message "Engine Maintenance Required" only comes on when you have turned on the A/C. The coolant bypass valve's main purpose is to shut off engine coolant flow to the heater when the A/C is operating.