Note. For circuit reference, see WIRING DIAGRAMS article.
Circuit Description
Changes in fuel delivery will be indicated by long term and short term fuel trim values that are displayed on scan tool. Ideal fuel trim valve is about zero percent. PCM will add fuel when oxygen sensor signal is indicating a lean condition. PCM will reduce fuel when oxygen sensor signal is indicating a rich condition. Additional fuel is indicated by fuel trim values that are greater than zero percent. Fuel reduction is indicated by fuel trim values that are less than zero percent.