Secondary Air Injection

SECONDARY AIR
To get the catalytic converter working as soon as possible after a cold start, ambient air is pumped into the exhaust manifold where the oxygen in the air starts a chemical combustion process together with C0, HC and NOx pollutants, thus generating heat.

About ten seconds after the engine fires, the secondary air injection pump starts and a solenoid valve opens the passage leading to the exhaust manifold.

Since this process is dependent on both time and temperature, the solenoid valve closes and the pump stops either when a maximum of 120 seconds has elapsed or when engine temperature reaches 70°C (158°F), whichever occurs first.





PRINCIPLE OF OPERATION, SECONDARY AIR INJECTION

Secondary Air Injection Pump
Roughly between one second (hot engine) and five seconds (cold engine) after the engine has started, the control module grounds pin 23 and causes the secondary air injection pump relay to operate and supply the pump and solenoid valve with current.

The length of time during which the control module grounds pin 23 (air injection pump and valve activated) is temperature dependent, so that the maximum connection time is 100 seconds for a cold engine (below 20°C) and 15 seconds for a hot engine (above 70°C).

No connection of the secondary air injection system occurs at engine temperatures above 78°C (162°F).