Secondary Air Injection (AIR) System Diagnostic (MOTRONIC)

Requirements
The secondary air injection diagnostic must verity that turning on the electrically-driven secondary air pump has a real and measurable effect on the operation of the system. The secondary air injection system will be considered to be malfunctioning when it's failure to operate or improper operation will cause emission levels to increase to more than 1.5 times the FTP standards.

Theory of Diagnostic Operation
A secondary air system failure will turn on the MIL if a malfunction is detected during two consecutive driving cycles. The diagnosed procedure runs once per trip and is based on observing the reaction of the short term fuel after the secondary air pump has been turned on. The large increase in 9xygen entering the exhaust system when the pump is running will drive down the output voltage from the pre-catalyst heated oxygen sensor, affecting the short term fuel trim. If, on two consecutive trips, the short term fuel trim does not increase by approx. 12% within 20 seconds when the secondary air system is active, the MIL will be requested and a DTC set.

Secondary Air Injection Enabling Criteria
The secondary air diagnostic test will run when:

^ The diagnostic check has not been completed yet this trip.
^ Vehicle speed is 0.
^ The engine is idling.
^ The fuel system is operating in closed loop.

Hardware Required
No additional equipment needed to be added to permit diagnosis of the secondary air injection system. Diagnosis is carried out by observing the activity of existing components.