Circuit Description

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.

Air/Fuel (A/F) sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to control air/fuel ratio. A/F sensor includes a heater and may also be referred to as A/F ratio sensors. Heated A/F sensors are located on each exhaust manifold. Heated A/F sensor on rear (firewall side) exhaust manifold may also be referred to as bank No. 1 sensor No. 1. Heated A/F sensor on front (radiator side) exhaust manifold may also be referred to as bank No. 2 sensor No. 1. DTC P1135 is for A/F sensor bank No. 1 sensor No. 1. DTC P1155 is for A/F sensor bank No. 2 sensor No. 1. DTC is set when A/F sensor heater output is more than 8 amps or when heater output is less than .25 amp. If DTC exists, ECM will operate in fail-safe mode. Possible causes are:

A/F sensor heater circuit is open or shorted.
Defective A/F sensor heater.
Defective ECM.