K 1500 Truck 4WD V8-4.8L VIN V (1999)
Oxygen Sensor: Description and Operation
Front Heated Oxygen Sensors (HO2S)
The Heated Oxygen Sensors are mounted in the exhaust system where they can monitor the oxygen content of the exhaust gas stream. The oxygen
present in the exhaust gas reacts with the sensor to produce a voltage output. This voltage should constantly fluctuate from approximately 100 mV (high
oxygen content = lean mixture) to 900 mV (low oxygen content = rich mixture). The heated oxygen sensor voltage can be monitored with a scan tool. By
monitoring the voltage output of the oxygen sensor, the PCM calculates the fuel pulse width command to give to the injectors (lean mixture/low HO2S
voltage = rich command, rich mixture/high HO2S voltage = lean command).
The PCM sets the following DTCs when the PCM detects an HO2S signal circuit that is low:
^
DTC P0131 Bank 1 left front HO2S.
^
DTC P0151 Bank 2 right front HO2S.
^
DTC P0137 Bank 1 left rear HO2S.
^
DTC P0157 Bank 2 right rear HO2S.
The PCM sets the following DTCs when the PCM detects an HO2S signal circuit that is high:
^
DTC P0132 Bank 1 left front HO2S.
^
DTC P0152 Bank 2 right front HO2S.
^
DTC P0138 Bank 1 left rear HO2S.
^
DTC P0158 Bank 2 right rear HO2S.
The PCM sets the following DTCs when the PCM detects no HO2S activity:
^
DTC P0134 Bank 1 left front HO2S.
^
DTC P0154 Bank 2 right front HO2S.
^
DTC P0140 Bank 1 left rear HO2S.
^
DTC P0160 Bank 2 right rear HO2S.
A fault in the heated oxygen sensor heater element or its ignition feed or ground results in an increase in time to Closed Loop fuel control. This may
cause increased emissions, especially at start-up. The following DTCs set when the PCM detects a malfunction in the HO2S heater circuits:
^
DTC P0135 Bank 1 left front HO2S heater.
^
DTC P0155 Bank 2 right front HO2S heater.
^
DTC P0141 Bank 1 left rear HO2S heater.
^
DTC P0161 Bank 2 right rear HO2S heater.
The PCM also has the ability to detect HO2S response, switching, transition time, and incorrect ratio voltage problems. The PCM stores a DTC that
indicates degraded HO2S performance if a HO2S response switching, transition time, or ratio problem is detected.
