Test Group TBM5.4VJGFEK

Secondary Air System Monitoring General Description -  At cold start, secondary air pump and valve are switched on for their normal operating function. Secondary air delivered into exhaust gas is causing an increase of the lambda sensor signal until it reaches a predetermined value. This fixed limit corresponds to the minimum amount of secondary air (low flow limit check). For secondary air system monitoring flow chart, see Fig 1.

Check Conditions -  To start diagnosis, several condition have to be satisfied:

• Secondary air system is on.
• No error from coolant temperature sensor.
• Lambda sensor is heated up (stabilizes condition).
• No error from the fuel system.
• Altitude driving conditions below 8000 ft.
• No output stage error from the evaporative system.
• No error from secondary air pump relay.
• Closed evaporative system purge valve.

Furthermore, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted.

Check Procedure - 

• All adaptions of the fuel system are inhibited.
• Closed loop function of lambda control is inhibited.
• Secondary air pump and valve will be switched on.
• In case of not reaching fixed limit by lambda sensor signal, a fault will be detected and stored in the memory.
• Diagnosis procedure will be ended and secondary air system resumes its operating function.