Firebird V8-5.7L VIN G (2001)
^
Cause a false failure for a normally-functioning catalyst
^
Prevent the diagnostic from running
Some contaminants that may be encountered are phosphorus, lead, silica, and sulfur. The presence of any of these contaminants will reduce catalyst
efficiency, and will lead to emission failures.
Catalyst Monitor Heated Oxygen Sensors
In order to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides Of Nitrogen (NOx), the system uses a 3-way catalytic
converter. The catalyst promotes a chemical reaction which oxidizes the HC and the CO present in the exhaust gas, converting these chemicals to
harmless water vapor and to carbon dioxide. The catalyst also reduces NOx, converting the NOx to nitrogen. Each catalyst monitor HO2S, or the
post-catalyst HO2S, is always located downstream of the catalytic converter.
The PCM can monitor this process using the post-catalyst HO2Ss. The pre-sensors produce an output signal, which indicates the amount of oxygen
present in the exhaust gas entering the 3-way catalytic converter. The post sensor produces an output signal which indicates the oxygen storage capacity
of the catalyst. The oxygen storage capacity indicates the catalyst's ability to efficiently convert the exhaust gases. If the catalyst is operating efficiently,
the pre-HO2S signal will be tar more active than the signal produced by the post HO2S.
In addition to catalyst monitoring, the post-heated oxygen sensor has a limited role in controlling the fuel delivery. If the post-HO2S signal indicates a
high oxygen content or a low oxygen content for an extended time while in a closed loop, the PCM adjusts the fuel delivery slightly in order to
compensate.
Comprehensive Component Monitor Diagnostic
Comprehensive component monitoring diagnostics are required in order to monitor the emissions-related input and output Powertrain components.
Input Components
The PCM monitors the input components for circuit continuity and for out-of-range values. The monitoring includes performance checking.
Performance checking refers to indicating a fault when the signal from a sensor does not seem reasonable, for example, a throttle position sensor that
indicates a high throttle position during low engine loads or during low MAP voltage. The input components may include but are not limited to the
following sensors:
^
The Vehicle Speed (VSS) Sensor
^
The Accelerator Pedal Position (APP) sensor, if the vehicle has this equipment
^
The Mass Airflow (MAF) sensor
^
The Intake Air Temperature (IAT) sensor
^
The Crankshaft Position (CKP) sensor
^
The Knock Sensor (KS)
^
The Throttle Position (TP) sensor
^
The Engine Coolant Temperature (ECT) sensor
^
The Camshaft Position (CMP) sensor
^
The Manifold Absolute Pressure (MAP) sensor
In addition to the circuit continuity and rationality check, the ECT sensor is monitored for its ability to achieve a steady state temperature in order to
enable the closed loop fuel control.
Output Components
Diagnose the output components for the proper response to the PCM commands. Components where functional monitoring is not feasible will be
monitored for circuit continuity and for out-of-range values if applicable.
The output components to be monitored include, but are not limited to, the following circuits:
^
The Idle Air Control (IAC) motor
^
The EVAP system
^
The electronic transmission controls
^
The A/C relay
^
The cooling fan relay
^
The VSS output
^
The MIL control
^
The cruise control inhibit, if the vehicle has this equipment
Computers and Control Systems Information
The driveability and emissions information describes the function and operation of the PCM.
The engine controls information contains the following:
^
The component locations
^
The wiring diagrams
^
The PCM terminal end views and the terminal definitions
^
The Powertrain On-Board Diagnostic (OBD) System Check
^
The Diagnostic Trouble Code Tables (DTCs)
