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.

PCM supplies a bias voltage of about 450 mV between HO2S high and low circuits. When measured with a 10 megohm DVOM, display may be as low as 320 mV. HO2S varies voltage within about 1000 mV when exhaust is to rich, down to about 10 mV when exhaust is lean. PCM constantly monitors HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If Bank 1 HO2S voltage remains at or near 450 mV bias for an extended period of time, DTC P0134 will set, indicating an open HO2S signal or HO2S low circuit.

When DTC sets, PCM illuminates MIL as soon as fault was detected. PCM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data. Vehicle with operate in Open Loop mode only.

PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC P0134 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.