Diagnostic Aids

Check for a restriction in inlet air passage. A duct or inlet hose that collapses when hot or is blocked by debris can cause DTC to set. Ensure fuel pressure is within specifications. Fuel pressure that is too high will cause a rich condition. Check MAP sensor for correct values. A MAP sensor that reads low vacuum will cause a rich condition. When MAP sensor is disconnected, ECM will substitute a default value. If rich condition goes away, replace MAP sensor and recheck system. Check for fuel contamination. Small amounts of water in fuel tank can cause DTC to set. Check HO2S for silicone and other contaminants.

Check for a poor ECM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.