Diagnostic Aids

DTC P0133 or slow response is most likely caused by one of following items:

• Fuel pressure - The system will go rich if fuel pressure is too high. The PCM/ECM can compensate for some increase, but if it gets too high a DTC P0133 may set.
• Leaking injector - A leaking or malfunctioning injector can cause system to go rich.
• Manifold Absolute Pressure (MAP) sensor - An output that causes PCM/ECM to sense a higher than normal manifold pressure (low vacuum) can cause system to go rich. Disconnecting MAP sensor will allow PCM/ECM to set a fixed value for MAP sensor. Substitute a different MAP sensor if rich condition is gone while sensor is disconnected.
• Pressure regulator - Check for a leaking fuel pressure regulator diaphragm by checking for presence of liquid fuel in vacuum line to pressure regulator.
• Throttle Position (TP) sensor - An intermittent TP sensor output can cause system to go rich due to a false indication of engine accelerating.
• O2S1 contamination - Inspect O2S1 for silicone contamination from fuel or use of improper Room Temperature Vulcanizing (RTV) sealant. The sensor may have a white powdery coating, resulting in a high but false voltage signal (rich exhaust indication). The PCM/ECM will then reduce amount of fuel delivered to engine causing a severe surge or driveability problem.