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BigBob, Shop manager/Service Manager
Category: Toyota
Satisfied Customers: 4838
Experience:  Shop Manager with 25 years experience
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2002 toyota sienna: obd code..fuel 1 sensor

Customer Question

obd code for 2002 toyota sienna reads P1155
Air/fuel sensor heater circuit (bank 1 sensor 2 )
Where is this sensor ? And what does this control ?
Thanks -Chris
Submitted: 7 years ago.
Category: Toyota
Expert:  BigBob replied 7 years ago.

Actually that code is for ban2 sensor 1
P1155 - A/F Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)


The A/F sensor has the characteristic that provides output voltage* approximately proportional to the existing air-fuel ratio. The A/F sensor output voltage* is used to provide feedback for the ECM to control the air-fuel ratio.

By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air-fuel ratio and control the proper injection time immediately. If the A/F sensor is malfunctioning, ECM is unable to perform accurate air-fuel ratio control.

The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection.

*: The voltage value changes at the inside of the ECM only.

This is the most common failure on a Toyota air fuel sensor, the heater circuit. If you replace the unit only use and air fuel sensor, not an oxygen sensor.

Let me know if I can help further,
BigBob and 2 other Toyota Specialists are ready to help you
Customer: replied 7 years ago.
Hi Bob, so its the A/F sensor right in the front thats the most accessible?
Expert:  BigBob replied 7 years ago.
yes that is correct