Air Injection: Testing and Inspection

MONITOR OF SECONDARY AIR SYSTEM

Function Modules:






Principle of algorithm:

1. Evaluation during normal operation of secondary air injection (=SAI):












2. Evaluation after deactivation of SAI:
- Check of pilot control and reject result, if threshold exceeded.
- Adaption of pilot control directly after deactivation of SAI.

3. Fault evaluation:






Passive Monitors
The SAI is monitored only during normal operation of the secondary air injection system. The monitor of the SAI system is an air mass flow check to detect:
- a failure of the secondary air pump or
- a blocking or leaking between secondary air pump and exhaust manifold

The SAI monitor observes the calculated relative secondary air mass flow after engine start during catalyst heating. If this value is above a threshold the SAI will work properly.

Monitoring conditions for SAI monitor:
- upstream oxygen sensors are ready to measure
- lambda control ready for operation,
- altitude correction for fuel injection > calibration,
- air mass flow in between calibrated threshold,
- gradient of air mass flow < calibration,
- intake air temperature in between calibrated thresholds,
- engine coolant temperature in between calibrated thresholds,
- monitoring is prohibited through malfunction of other functions:
- e.g. faults of engine coolant temperature sensor, air charge sensor, intake air temperature sensor, SAI power stages, leak detection system, canister purge power stages, oxygen sensor(s) pre-catalyst, misfire, battery voltage, mixture system

Diagnosis of Secondary Air System - Overview Passive SAI Monitor