Secondary Air System Monitoring: Notes

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To reduce HC and CO emissions while engine is warming up, system uses a secondary air injection system. Immediately following a cold engine start, fresh air/oxygen is injected directly into the exhaust manifold. By injecting oxygen into exhaust manifold, warm up time of catalyst is reduced and oxidation of hydrocarbons is accelerated. Activation period of air pump can vary depending on engine type and operating conditions. See SECONDARY AIR SYSTEM MONITORING table.

SECONDARY AIR SYSTEM MONITORING

Requirement	Status/Condition
Oxygen Sensor	Open Loop
Oxygen Sensor Heating	Active
Engine Coolant Temperature	14 to -40°F (-10 to -40°C)
Engine Load	Predefined Range
Engine Speed	Predefined Range
Fault Codes	No Secondary Air Faults Currently Present
Average Lambda Value Deviation	Steady/Stable Load

System components include electric air injection motor/pump, electric motor/pump relay, non-return valve, vacuum/vent valve, stainless steel air injection pipes, vacuum reservoir, vacuum reservoir check valve, and in-line resistor for speed control (V12 engine only).

Secondary air injection system is monitored via use of pre-catalyst oxygen sensor(s). Once air pump is active and is air injected into system, signal at oxygen sensor will reflect a lean condition. If oxygen sensor signal does not change within a predefined time, fault will be set and identify the faulty bank(s). If after completing the next cold start and a fault is again present, CHECK ENGINE light will be illuminated.