Method for vehicle emission control

Abstract

A method for vehicle emission control is provided. In one example, a method for an engine may include indicating degradation of a hydrocarbon trap based on an amount of NH3 in exhaust gas in responseto satisfying a plurality of diagnostic entry conditions. In some examples, the NH3 amount may be determined based on one or more NOx sensor outputs. In some examples, the plurality of diagnostic entry conditions may include that the engine has been in operation immediately after an engine cold start for an initial duration. When the NH3 amount is determined from the one or more NOx sensor outputs, conditions of the exhaust gas after cold start of the engine may be utilized in good time. In some examples, a predetermined air-fuel ratio may actively provide the exhaust gas to satisfy at least one of the plurality of diagnostic entry conditions.

Description

technical field

[0001] The present description generally relates to methods for controlling exhaust emissions based on the presence of ammonia in exhaust emissions from a vehicle. Background technique

[0002] Regulations on vehicle emissions are trending toward stricter policies aimed at mitigating chemical compounds that can cause damage to macro-ecosystems and the global climate. To address such regulations, component catalysts of exhaust treatment systems may be developed to mitigate one or more of these potentially problematic chemicals in conjunction with other component catalysts of the exhaust treatment system. As an example, nitrogen oxides (NO x ), hydrocarbon (HC) and carbon monoxide (CO) emissions.

[0003] For example, an HC trap may be employed to trap at least HC emissions in the exhaust stream during conditions where other component catalysts may not have reached appropriate light-off temperatures (e.g., immediately after a cold engine start) . When the e...

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