Diagnostic Aids
WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
- The system will go rich if fuel pressure is to high. The PCM can compensate for some increase, however, if the pressure becomes too high, DTC P0172 will be set.
- A leaking or malfunctioning injector can cause the system to go rich.
- An output that causes the PCM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the PCM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone while the sensor is disconnected.
- Check for a leaking fuel pressure regulator diaphragm by checking for the presence of liquid fuel in the vacuum line to the regulator.
- An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating.
- Inspect the O2S 1 for silicone contamination from fuel or from use of an improper RTV sealant. The sensor may have a White powdery coating and result in a high but false voltage signal, rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem.