Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2000 Pontiac Firefly (CANADA) L3-1.0LFACTORY OEM SERVICE PROCEDURE
Self-Diagnosis Function
The Powertrain Control Module (PCM) diagnoses any troubles which may occur in the engine control system when the ignition switch is in the ON position with the engine running. The PCM indicates a malfunction by illuminating the Malfunction Indicator Lamp (MIL) when a fault occurs in any of the following systems:
^ Heated Oxygen Sensor 1 (HO2S 1)
^ Heated Oxygen Sensor 2 (HO2S 2)
^ Engine Coolant Temperature (ECT) sensor
^ Throttle Position (TP) sensor
^ Vehicle Speed Sensor (VSS)
^ Intake Air Temperature (IAT) sensor
^ Manifold Absolute Pressure (MAP) sensor
^ Camshaft Position (CMP) sensor
^ Crankshaft Position (CKP) sensor
^ Exhaust Gas Recirculation (EGR) system
^ Evaporative Emission (EVAP) system
^ Idle Speed Control (ISC) system (including the CTP switch)
^ Early Fuel Evaporation (EFE) heater
^ Misfire Detection
^ Fuel-trim
^ Catalyst Monitor
^ Cooling Fan Control
^ Central Processing Unit (CPU) of the PCM
When the PCM detects a malfunction in one of the above areas, the PCM will illuminate or flash the MIL in order to notify the driver of the occurrence of a fault. The PCM will store a Diagnostic Trouble Code (DTC) when the PCM illuminates the MIL.
The PCM will turn Off the MIL after 3 consecutive ignition cycles (in which the diagnostic runs) without the malfunction occuring. The DTC will remain stored in the PCM memory after the MIL is Off.
^ Heated Oxygen Sensor 1 (HO2S 1)
^ Heated Oxygen Sensor 2 (HO2S 2)
^ Engine Coolant Temperature (ECT) sensor
^ Throttle Position (TP) sensor
^ Vehicle Speed Sensor (VSS)
^ Intake Air Temperature (IAT) sensor
^ Manifold Absolute Pressure (MAP) sensor
^ Camshaft Position (CMP) sensor
^ Crankshaft Position (CKP) sensor
^ Exhaust Gas Recirculation (EGR) system
^ Evaporative Emission (EVAP) system
^ Idle Speed Control (ISC) system (including the CTP switch)
^ Early Fuel Evaporation (EFE) heater
^ Misfire Detection
^ Fuel-trim
^ Catalyst Monitor
^ Cooling Fan Control
^ Central Processing Unit (CPU) of the PCM
When the PCM detects a malfunction in one of the above areas, the PCM will illuminate or flash the MIL in order to notify the driver of the occurrence of a fault. The PCM will store a Diagnostic Trouble Code (DTC) when the PCM illuminates the MIL.
The PCM will turn Off the MIL after 3 consecutive ignition cycles (in which the diagnostic runs) without the malfunction occuring. The DTC will remain stored in the PCM memory after the MIL is Off.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.