C 1500 Truck 2WD V6-262 4.3L VIN Z (1992)
The control module puts out a reference signal of 0.45 volts (450 mV). The reference signal serves two purposes. The first is to run the engine when it
is in OPEN LOOP mode of operation. When the air/fuel ratio is correct the control module senses 450 mV. When the engine is operating with a rich
air/fuel ratio there is a reduction of free oxygen in the exhaust stream and the O2 sensor voltage rises above the reference voltage.
When the engine is running lean the voltage drops below the reference voltage due to the excess oxygen in the exhaust stream. The O2 sensor provides
the feedback information for the CLOSED LOOP operating mode of the fuel delivery system. The O2 sensor indicates to the control module what is
happening in the exhaust. It does not cause things to happen. It is a type of gauge: Low voltage output = lean mixture = high oxygen content in the
exhaust; high voltage output = rich mixture = low oxygen content in the exhaust.
CONDITIONS THAT CAN SET CODES
An open O2 sensor, should set a Diagnostic Trouble Code (DTC) 13. A constant low voltage in the O2 sensor circuit should set a DTC 44. A constant
high voltage in the circuit should set a DTC 45. DTC 44 and DTC 45 could be set as a result of fuel system problems. REFER TO COMPUTERS
AND CONTROL SYSTEMS/DIAGNOSTIC CHARTS for diagnosis of these codes.
HEATED OXYGEN SENSOR TYPE
The heated oxygen sensor works in the same manner as the non-heated oxygen sensor. The exception is that B+ is supplied to a heating element that is
part of the sensor itself. The heater helps the control module control the fuel injection sooner for better fuel emissions. There are no Diagnostic
Trouble Codes (DTC's) to detect if the heater part of the sensor is working. To check the heater, REFER TO COMPUTERS AND CONTROL
SYSTEMS/DIAGNOSIS AND TESTING PROCEDURES/OXYGEN SENSOR TESTING.
