Air Injection: Testing and Inspection
Secondary Air Injection (AIR) System:
- The secondary air injection diagnosis consists of a flow test and a leak test. These are two diagnostic versions, one diagnosis is conducted under normal Customer Operations, the other a targeted, retrievable Workshop Diagnosis. Because of the V6 engine, diagnosis is conducted for both banks.
OBD II CHECKS THE FOLLOWING:
- Flow in the multi-function valve,
- Flow in the Secondary Air Injection pump,
- Electrical function of the switching valve with the aid of comprehensive components diagnosis,
- Electrical function of the pump relay.
Process:
- An activated secondary air injection system leads to an increase in oxygen content in the exhaust through the air flow in the secondary air pump. This is acquired by the Pre-CAT 2 sensors (reduced 2-sensor voltage) and sent to the engine control module.
- If engine management gives the opening-signal to the secondary air injection valve and switches on the pump, an extremely lean mixture is found at the 2-sensors, if the secondary air system is OK. The 2-sensor control indicates a clear standard tolerance.
CUSTOMER OPERATIONS
Flow Diagnosis:
- During customer operation the flow diagnosis takes place during normal pump running time after an engine start at temperature range +8°C to +55°C, and the pump running time is constant and vehicle is driven at low load/rpm.
Leak Test:
- The leak test during customer operation occurs after the following conditions are attained:
- Flow test beforehand is OK
- Idle
- Engine Coolant temperature > 70°C (158°F)
- Time after engine start 16 minutes
- For leak test the secondary air pump is switched on when idling warm. The multi-valve remains closed. Is the system leakproof, then the ~control does not react with an enrichment. The customer-leak test is only conducted if the customer flow diagnosis ends with an OK.
WORKSHOP DIAGNOSIS:
- To begin a targeted diagnosis (workshop diagnosis) of the secondary air injection system select "Basic Setting" function 04 and input display group 020 or 021.
- This was made in order to conduct a diagnosis in the workshop without the mandatory condition of a cold start in idle.
- This workshop diagnosis is conducted one time only per engine start. The engine coolant temperature must be higher than 70°C (158°F).
Flow diagnosis (Display group 20):
- During the flow test, oxygen sensor control is shut off (the engine is running rich at this time). Simultaneously, the secondary air injection pump is switched on, thereby supplying fresh air into the exhaust manifold, increasing the oxygen percentage in the exhaust. The Heated Oxygen Sensor (HO2S) now detects higher oxygen content in the exhaust, usually the indication of a lean mixture.
- To confirm the test, the engine control module checks for indication of a lean mixture over a specific time period. This means that the secondary air injection system supplies a sufficient amount of air and the system is OK.
Leakage diagnosis (Display group 21):
- A confirmed flow test is a requirement for the leakage test. With a warm engine the secondary air injection pump is switched on at idle. The combination valves however, are not triggered by the secondary air injection intake valves, meaning that they remain closed. When switching on the secondary air injection pump, Oxygen Sensor (02S) control from the ECM is monitored.
- If the system is tight (not leaking) fresh air cannot enter the exhaust manifold, and 02S control should must not react (rich or lean).
- If the system is not tight (leaks), 02S control must react to the lean mixture (with oxygen in the secondary air injection inlet) with a clear enrichment of the mixture, and this enrichment is recognized by the engine control module.