Circuit Description

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

To provide best possible combination of driveability, fuel economy and emission control, a closed loop air/fuel metering system is used. While in closed loop, PCM monitors Bank 1 HO2S-1 signal and adjusts fuel delivery based on HO2S signal voltage. Changes made to fuel delivery will be indicated by long and short term fuel trim values that can be monitored with a scan tool. Ideal fuel trim values are about zero percent. If HO2S signal indicates a lean condition, PCM will add fuel, resulting in fuel trim values more than zero percent. If a rich condition is detected, PCM will reduce fuel delivery, resulting in fuel trim values less than zero percent. If an excessively lean condition is detected on Bank 1, DTC P0171 will set. The PCMs maximum authority to control long term fuel trim allows a range between -14 and 20 percent. PCM monitors fuel trim under various engine speed/load fuel trim cells before determining status of fuel trim diagnostic.

When DTC sets, PCM illuminates MIL on second trip after fault was detected. PCM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data.

PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC P0171 will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.