Ageing failure diagnosis method of engine catalytic converter

Abstract

The invention provides an ageing failure diagnosis method of an engine catalytic converter, which comprises the steps of: enabling condition judgment, first stage monitoring, second stage monitoring, oxygen storage time calculation, diagnosis judgment and failure diagnosis report, wherein the oxygen storage time calculation also comprises a special diagnosis mode, and can fully consider various conditions generated during the failure diagnosis; judgment conditions are more complete and full and can send related information to an OBD failure diagnosis unit under the condition of incapability of diagnosis so as to be convenient for accurately diagnosing the state of the catalytic converter and preventing from generating error judgment, such as incapability of carrying out failure diagnosis.By using the method, reasons of incapability of carrying out failure diagnosis can be known.

Description

technical field [0001] The invention relates to a fault diagnosis method for an engine catalytic converter, in particular to a method for diagnosing an engine catalytic converter aging fault with an on-board diagnosis (OBD) function. Background technique [0002] In the engine online diagnosis (OBD) system, it is necessary to ensure the normal operation of the catalytic converter connected to the engine exhaust pipe. When the limit value is 0.4g / km, the OBD system warning light should light up and record the fault information. [0003] Typically, the diagnosis of catalytic converter degradation is based on detecting the oxygen storage time (OSC) of the catalytic converter. Such as figure 1 As shown, when the catalytic converter 10 is in a normal working state, the voltage output value of the upstream oxygen sensor 261 fluctuates up and down with the operating conditions of the engine, but the voltage output value of the downstream oxygen sensor 262 is basically a straight ...

AI Technical Summary

Problems solved by technology

[0007] Disclosed in the U.S. Patent 6,694,243 is a diagnostic method for catalytic converter failures, in which the diagnostic process includes the judgment of diagnostic enabling conditions such as engine idle speed, but the objects of judgment are limited; in addition, the method is only based on the output results It is judged that the catalytic converter is working normally or there is a fault, but the cause of the abnormal output cannot be found out, thus affecting the authenticity and accuracy of the fault diagnosis result

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