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PO440, PO441, PO446, and P1135 Fault Codes on 2001 Toyota Sienna: Causes, Fixes, and Sensor Identification

Model: 2001 Toyota Sienna Fault Code: P0440 Posted: 2009-07-29 21:25

My 2001 Toyota Sienna with 155,000 miles has recently triggered several diagnostic trouble codes: PO440, PO441, PO446, and P1135. I took it to the dealership, where they suggested a faulty charcoal canister as the root cause. The repair estimate was over $400, including labor—something I couldn't afford. I continued driving it until I noticed a significant drop in fuel efficiency. Upon rechecking the codes, P1135 appeared, and now my vehicle won’t idle properly when cold; it only stabilizes after warming up. My main question: Is an Air/Fuel (A/F) sensor the same as an Oxygen (O2) sensor? If not, which one is relevant here, and how can I determine if it’s defective? Any guidance on diagnosis or repair options would be greatly appreciated.

Related fault codes
P0440P0441P0446P1135
Comments (5)
Anonymous 2009-07-30 06:52

In short, to a parts technician, an O2 sensor and an A/F sensor may sound similar—but they are fundamentally different. One is typically a wide-band O2 sensor, the other a conventional (narrow-band) O2 sensor. To avoid confusion, it's best to consult your Toyota dealer to ensure you're purchasing the correct part. The charcoal canister issue is also very common in many Toyota models and likely contributes to codes PO440, PO441, and PO446.

Anonymous 2009-07-30 06:54

P1135 refers to the Air/Fuel Sensor Heater Circuit Response (Bank 1, Sensor 1). While A/F sensors share some similarities with O2 sensors, they are not interchangeable. Testing via resistance measurement is possible, but in most cases, replacement is necessary for proper function.

Anonymous 2009-07-30 15:00

Jeff Compton wrote: In short, to a parts technician, an O2 sensor and an A/F sensor may sound similar—but they are fundamentally different. One is typically a wide-band O2 sensor, the other a conventional (narrow-band) O2 sensor. To avoid confusion, it's best to consult your Toyota dealer to ensure you're purchasing the correct part. The charcoal canister issue is also very common in many Toyota models and likely contributes to codes PO440, PO441, and PO446. Hi Jeff—thanks for the clarification. If these sensors are similar but different, how can I tell which one is a wide-band O2 sensor versus a conventional one? To be safe, I’ll remove the sensor and take it to the dealer for proper diagnosis. Are there any specific tests available to confirm whether the charcoal canister is faulty? Any advice would be appreciated.

Anonymous 2009-07-30 16:04

Mohawkmtrs wrote: P1135 refers to the Air/Fuel Sensor Heater Circuit Response (Bank 1, Sensor 1). While A/F sensors share some similarities with O2 sensors, they are not interchangeable. Testing via resistance measurement is possible, but in most cases, replacement is necessary for proper function. Thanks for your input. Is Sensor 1 on Bank 1 the A/F sensor? If not, where would it be located? And what’s the difference between this sensor and a standard O2 sensor?

Anonymous 2009-07-31 15:09

The sensors look very similar and are typically mounted in the same exhaust location. However, a vehicle will have either one or the other—not both—depending on its design. The dealership staff should be able to identify which sensor is required based on your model year and engine configuration.