ABS & TPMS warning lights

My 2001 Sienna XLE has a problem. The ABS and TPMS lights both come on after a few miles of interstate driving at 70-75 mph. I can detect an intermittent vibration in the gas pedal before the warning lights come on. The front brake rotors and pads have been replaced and the tires have been regularly rotated and balanced. The warning lights go out once the engine is shut off so there are no stored codes (I have a code reader). I have shifted the trans in neutral when the vibration occurs to see if it goes away but it still continues. The engine was tuned back in April (plugs, timing belt, etc) so I do not believe it is an engine misfire. Could it be a bad CV/axle that is causing a vibration which makes the ABS & TPMS systems think there is a problem?

I just realized that the vibration goes away once the ABS & TPMS lights activate. My wife normally drives the Sienna and she confirmed that she had noticed this as well. What would cause a vibration that triggers the ABS & TPMS lights but goes away once the lights come on? Is the computer disabling something once it faults?

Anyone have any guesses on this? I really want to get it fixed before it causes a bigger problem.

Could be something simple like a wheel about to come off. A whole month and you havent had it looked at by a professional? Sounds strange that the vibration would stop when the warning lights come on!

Wheels are on tight. I am trying to avoid going to the dealership, hence my posts for help here on AF. I believe I can fix it myself if I could just get the problem properly diagnosed.

At this point I am starting to believe that it is a bad ABS/speed sensor or a bad tone ring (reluctor wheel). I just need to figure out which wheel and go from there. Speed sensors are about $200 each so I only want to replace them if they are bad. If it is the tone ring it will require an axle replacement. Axles are only $50-$70 each but again I only want to replace what is bad rather than throwing parts (and money) at the problem in hopes of hitting it right.

I have read on other posts that when the ABS light comes on the ABS system is disabled. It seems this would point towards a bad ABS sensor.

Wheels are on tight. I am trying to avoid going to the dealership, hence my posts for help here on AF. I believe I can fix it myself if I could just get the problem properly diagnosed.

At this point I am starting to believe that it is a bad ABS/speed sensor or a bad tone ring (reluctor wheel). I just need to figure out which wheel and go from there. Speed sensors are about $200 each so I only want to replace them if they are bad. If it is the tone ring it will require an axle replacement. Axles are only $50-$70 each but again I only want to replace what is bad rather than throwing parts (and money) at the problem in hopes of hitting it right.

I have read on other posts that when the ABS light comes on the ABS system is disabled. It seems this would point towards a bad ABS sensor.
Getting the problem diagnosed properly starts with getting the codes read. Without that the best anyone here can do for ya would be an educated guess.
The ABS is disabled when the light comes on but I dont see the direct corellation between this and a sensor failure. Some pocket scanners will read ABS codes. Or have it read by a professional. It may cost you something but it'll probably be less than the first wrong part you might buy!

I tried my code reader again but it showed no codes so I jumpered the Tc and E1 terminals on the diagnostic port under the hood (to the left of the oil dipstick). The ABS light flashed 4 codes - 32, 33, 34, and 41. If anyone knows what these codes mean, please let me know. In the meantime I will search the forums for the meanings of these codes.

Found the codes in my Haynes manual. 32 is sensor signal problem left front wheel, 33 is sensor signal problem right rear wheel, 34 is sensor signal problem left rear wheel and 41 is abnormally low battery positive voltage. So what does this indicate? Surely I don't have 3 bad sensors. ABS ECU?