Circuit Description

When vehicle is first started, computer system operates in open loop. Air/fuel ratio is determined by inputs from Engine Coolant Temperature (ECT), Throttle Position (TP) and Manifold Absolute Pressure (MAP) sensors. PCM will begin using input from HO2S(s) to control fuel delivery (closed loop operation) when vehicle obtains normal operating temperature. DTC P0125 will set when correct engine temperature required for closed loop operation is not reached within a predetermined amount of time.