Secondary Air Injection System Description
The secondary air injection (AIR) system helps reduce exhaust emissions.
The system forces fresh filtered air into the exhaust stream in order to accelerate
catalyst operation.
The system includes the following:
| • | AIR pump--The AIR pump supplies filtered air through the
secondary air injection system into the exhaust stream. The control module
provides ground for the pump relay, battery voltage is then applied to the
pump. The filter is the only serviceable part of the pump. |
| • | AIR vacuum control solenoid--The AIR vacuum control solenoid
controls the AIR shut-off valves. When the secondary air injection system
is enabled, the control module provides a ground to the solenoid. Enabling
the solenoid, allows engine vacuum to be applied to the AIR shut-off valves. |
| • | AIR shut-off valves--The AIR shut-off valves are vacuum operated.
When the secondary air injection system is enabled, vacuum is applied to
the valves. The vacuum opens the valves and allows air from the AIR pump
to flow to the check valves. |
| • | Check valve--The check valve prevents back flow of exhaust
gases into the secondary air injection system. An AIR pump that had become
inoperative and had shown indications of having exhaust gases in the outlet
port would indicate check valve failure. |
| • | Plumbing--The plumbing carries the air from the pump to the
exhaust stream. The plumbing includes the hoses, pipes and clamps. The plumbing
can be tested for leaks using a soapy water solution. With the AIR pump running,
bubbles will form if a leak exists. |
Results of Incorrect Operation
If no air (oxygen) flow enters the exhaust stream, the start up emission
levels will rise. The control module can detect a system flow problem using
the pre catalyst heated oxygen sensor (HO2S) and short term fuel trim (FT).
If a system flow problem is present the HO2S voltage will not indicate an
expected lean condition, short term FT will not increase and a DTC will set.
If incorrect voltage is present on the vacuum control solenoid or the
pump relay control circuits the device will not operate. This will be detected
by the control module and a DTC will set.
The following DTCs can set if a secondary air injection
fault is detected:
| • | DTC P0410--A system flow problem has been detected. |
| • | DTC P0412--A vacuum control solenoid control circuit
problem has been detected. |
| • | DTC P0418--A pump relay control circuit problem has
been detected. |
