Circuit Description

Heated oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. ECM uses input signal to determine fuel injection system operation. Heated oxygen sensors include a heater. DTCs are set when after engine is warmed up, heated oxygen sensor (bank 1, 2 sensor 1) output does not indicate RICH (0.45 volts or more) even once when engine speed is at 1400 RPM or more, vehicle speed is 25-81 MPH, and throttle valve does not fully close 180 seconds or more after starting engine for at least 65 seconds. Possible causes are:

• Open or short in heated oxygen sensor circuit.
• Defective heated oxygen sensor No. 1.
• Leaking air intake system.
• Fuel pressure problem.
• Faulty fuel injector.
• PCV.
• Gas leakage in exhaust system.
• Faulty ECM.