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 HO2S and Short Term 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:
| • | P0410 - A system flow problem has been detected. |
| • | P0412 - A vacuum control solenoid control circuit problem has
been detected. |
| • | P0418 - A pump relay control circuit problem has been detected. |
