Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Secondary Air System Monitoring: Notes
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.
| 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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.