Hello, I've searched but didn't find my question answered per se....so Wife drives a 08 toyota highlander hybrid 08, we are second owner, bought certified used. Hybrid battery replaced when we bought it. All updates and recalls applied...we have the limited trim level with 3rd row. All maintenance at dealer @ recommended intervals & services. So her mileage plummeted from 28 to 11mpg...same gas, same driver, same type & amount of driving. All the variables are the same except the huge drop in mpg. took it to dealer, replaced vehicle battery, reset ecu...no trouble codes, no errors. nothing. they drove it 11 miles plugged into diagnostic computer, they got 21 mpg....still less than before. the black box recorder reports my wife hit the brake & accelerator 176 times @ the same time....my wife isn't 2 foot driving, so I'm thinking the brake by wire system is faulting somehow. We are meeting the engineer @ dealership....hope he can help. Anyone have any ideas? thanks in advance for your help.

 

I'd say you found your issue but what exactly is causing the braking/accel events to happen at the same time is another story. Let us know what you find out from the engineer and hopefully we can shed some light on what's going on and get your fuel economy fixed.

What was the mileage on your Highlander when the traction battery was replaced?