Circuit Description

PCM uses a closed loop air/fuel metering system to provide the best possible combination of driveability, fuel economy and emission control. When vehicle is first started, PCM controls fuel delivery in an open loop mode. PCM ignores signal from fuel control HO2S and calculates air/fuel ratio from ECT, TP and MAF sensors.

PCM uses fuel control sensors (HO2S) to control fuel delivery (closed lop) when HO2S voltage signal is switching from less than 300 mV to greater than 600 mV, ECT greater than 183°F (84°C) and engine running for at least 2 minutes.

DTC will set when length of time for engine coolant to reach a stabilized temperature of 41°F (5°C) takes longer than it should. The amount of time ranges between 2-23 minutes depending on ECT at start-up and amount of air cycled by engine since start-up.