Firebird V8-5.7L VIN G (2001)
The component system includes the following items items:
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The component and circuit description.
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The on-vehicle service for each sub-system
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The functional checks and the diagnostic tables The DTCs also contain diagnostic support information containing circuit diagrams, circuit or
system information, and helpful diagnostic information.
Fuel Trim System Operation
The fuel trim system monitors the averages of the short-term and the long-term fuel trim values. If these fuel trim values stay at their limits for a
calibrated period of time, a malfunction is indicated. The fuel trim diagnostic compares the average of the short-term and the long-term fuel trim values.
If either value is within the thresholds, a pass is recorded. If either value is outside the thresholds, a rich or a lean fuel trim DTC will set.
Heated Oxygen Sensors (Pre-Catalyst)
The main function of the pre-catalyst Heated Oxygen Sensor (HO2S) is to provide the PCM with exhaust stream information in order to maintain the
proper fueling in order to hold the emissions within acceptable levels. These oxygen sensors are always located between the exhaust manifold and the
catalytic converter. After the sensor reaches the operating temperature, the sensor generates a voltage that is inversely proportional to the amount of
oxygen present in the exhaust gases.
The PCM uses the signal voltage from the fuel control heated oxygen sensors in a closed loop in order to adjust the fuel injector pulse width. While in a
closed loop, the PCM can adjust fuel delivery in order to maintain an Air/Fuel ratio which allows the best combination of emission control and
driveability.
If the oxygen sensor pigtail wiring, the connector, or the terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the
wiring, the connector, or the terminals. In order for the sensor to function properly, the sensor must have a clean air reference provided to it. This clean
air reference is obtained from the oxygen sensor wires. Any attempt to repair the wires, the connectors, or the terminals could result in the obstruction of
the air reference. Any attempt to repair the wires, the connectors, or the terminals will degrade the oxygen sensor performance.
Maintenance Schedule
Refer to the General Motors Maintenance Schedule for the appropriate service category for maintenance procedures that the owner or the technician
should perform in order to retain the emissions control performance.
Misfire Monitor Diagnostic Operation
The misfire monitor diagnostic is based on the crankshaft rotational velocity, or reference period, variations. The PCM determines the crankshaft
rotational velocity using the crankshaft position sensor and the camshaft position sensor. When a cylinder misfires, the crankshaft slows down
momentarily. By monitoring the crankshaft and the camshaft position sensor signals, the PCM can calculate when a misfire occurs.
For a non-catalyst damaging misfire, the diagnostic is required to monitor a misfire present for between 1000-3200 engine revolutions.
For catalyst damage misfire, the diagnostic responds to the misfire within 200 engine revolutions.
Rough roads may cause a false misfire detection. A rough road applies sudden torque variations to the drive wheels and to the drivetrain. This torque can
intermittently decrease the crankshaft rotational velocity. The ABS system detects uneven speed between the vehicles wheels and sends data via the
serial data bus to the PCM in order to disable the misfire monitor until the rough road is no longer detected.
On automatic transmission equipped vehicles, the Torque Converter Clutch (TCC) will disable whenever a misfire is detected. Disabling the TCC
isolates the engine from the rest of the drive line, and minimizes the effect of the drive wheel inputs on the crankshaft rotation.
When the TCC is disabled as a result of a misfire detection, the TCC will re-enabled after approximately 3200 engine revolutions if no misfire is
detected. The TCC remains disabled whenever the misfire is detected, with or without a DTC set. This allows the misfire diagnostic to reevaluate the
system.
