Diagnostic Aids
WARNING: This page is about a different car, the 2002 Pontiac Sunfire, 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0133 or slow response is most likely caused by one of the following conditions:
- The fuel pressure - system will go rich if the fuel pressure is too high. The PCM can compensate for some increase, but if the fuel pressure becomes too high, DTC P0172 may set. Diagnose fuel system.
- A leaking injector - a leaking or malfunctioning injector can cause the system to go rich.
- The MAP sensor - an output that causes the PCM to sense a higher than normal manifold pressure, or a 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 MAP sensor is disconnected.
- The pressure regulator - inspect for a leaking fuel pressure regulator diaphragm by confirming the presence of liquid fuel in the vacuum line to the fuel pressure regulator.
- The TP sensor - an intermittent TP sensor output can cause the system to go rich due to a false indication of the engine accelerating.
- HO2S 1 contamination - inspect the HO2S 1 for silicone contamination from fuel or from the use of an improper RTV sealant. The HO2S 1 may have a White powdery coating which will result in a high but false voltage signal, indicating a rich exhaust. The PCM will then reduce the amount of fuel delivered to the engine, causing a severe surge or driveability problem.