Last night when accelerating from 40 to 60 mph I felt a “whoosh” and then the RMPs went to 3000 when I had my foot on the pedal. They dropped to 1200 if I let off. This morning the car would shift into reverse, but punching the accelerator did nothing. Other gears are fine. I rolled out of the drive, stopped at the mech and diagnostics showed only a bad speed sensor. I saw a post elesewhere that had a similar issue in 2006, same model Toyota Sienna 2000 xle. Mech pricing the transmission replacement. Could it just be malfunctioning speed sensor sending bad data to the ECM? Is there hope for me?
Reverse on this transmission does not use speed sensors or electronic control. The absence of reverse drive indicates a major problem with the transmission.
I assume that the mechanic has checked the level, color, and odor of the fluid. If every thing is okey there, a line pressure check should be done in reverse to verify the operation of the pump and the pressure regulator. If the trans tech has the equipment, a line pressure check while the transmission trys to shift in drive and/or overdrive.
I am concerned that the high/reverse clutch in the transmission has failed. This would leave you in second in the forward gears. It is possible that the Transmission Control Module could command overdrive even though the transmission is still in second instead of high. That would reduce maximum engine RPM yet still give the van freewheeling with throttle backoff.
Anyway, it looks like you have an internal problem that part replacement and/or further diagnosis will not solve.
BTW what was the Diagnostic Trouble Code that was pulled, i.e. the exact PXXXX code.
Good luck on this. Keep us appraised of the outcome and any post mortum done on the transmission.