PINPOINT TEST HF: Catalyst Efficiency Monitor and Exhaust Systems: Introduction
Do not disconnect, disable, or touch the high voltage cables, components, or wiring during the module reprogramming procedure because high voltage is present. The high voltage warning labels containing the high voltage symbol are located on each high voltage component. High voltage cables and wiring are orange in color. Failure to follow these instructions may result in personal injury or death.
Appropriate repair methods and procedures are essential for the safe, reliable operation of all motor vehicles, as well as the personal safety of the individual doing the work. This article provides general directions for repairing vehicles with tested, effective techniques. Following them helps to establish reliability. There are numerous variations in procedures, techniques, tools, and parts for repairing vehicles, as well as in the skill of the individual doing the work. This article cannot possibly anticipate all such variations and provide advice or cautions as to each. Accordingly, anyone who departs from the instructions provided in this article must first establish that they compromise neither their personal safety nor the vehicle integrity by their choice of methods, tools, or parts.
This pinpoint test is intended to diagnose the following:
- catalytic converter
- exhaust system
The catalyst efficiency monitor uses precatalyst and post catalyst heated oxygen sensors (HO2S) to infer the hydrocarbon (HC) efficiency based on the oxygen storage capacity of the catalyst. Under normal, closed-loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the post catalyst HO2S (B) very slow and reduces the amplitude of those switches as compared to the switching frequency and amplitude of the precatalyst HO2S (A). As catalyst efficiency deteriorates due to thermal and chemical deterioration, its ability to store oxygen declines. The post catalyst HO2S (B) signal begins to switch more rapidly with increasing amplitude, approaching the switching frequency and amplitude of the precatalyst HO2S (A).
For additional information refer toCATALYST EFFICIENCY MONITOR and Catalyst and Exhaust Systems.