Secondary Air Injection

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

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

Since this process is dependent on both time and temperature, the solenoid valve closes and the pump stops either when a maximum of 80 seconds has elapsed or when engine temperature reaches 65°C (149°F), whichever occurs first.

At an engine temperature of 20° (68°F) the pump runs for about 80 seconds.

The pump will start only if the temperature of both the intake air and the coolant is between +1°C and +35°C (33°F - 95°F).





Principle Of Operation, Secondary Air Injection Pump
Roughly five seconds after the engine has started, the control module grounds pin 26 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 26 (air injection pump and valve activated) is dependent on time and temperature, so that the maximum connection time is 80 seconds or until engine temperature rises to 6°C (150°F), whichever occurs first.

No connection of the secondary air injection system occurs at engine temperatures below 1°C (33°F) or above 35°C (95°F).