2001 Toyota Sienna Check Engine Light ON

P0135 O2Sensor Heater Circuit Malfunction (Bank #1 Sensor #1)

The P0135 refers to the Heater on your oxygen sensor (it is built into the oxygen sensor) in the exhaust system. You can buy an after market sensor a lot cheaper than at the dealer. You have two sensors in the exhaust line before the Catalytic converter and one after for a total of 3. The Bank 1, Sensor 1 is the one on the back side of the engine next to the fire wall. I purchased an after market for my Sienna for about $150.00 and replaced it myself. Must be done when the engine is cold, other wise the exhaust will burn you. Looks like the P0135 is the factory code and the P1135 is an after market code from all the information I have been able to find.

Thanks for the information. It helps. BTW, I found that the OEM parts can be bought up to 30% off the retail price. -Cheers.