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 valve. When the AIR 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 valve. |
| • | AIR shut-off valve--The AIR shut-off valve is vacuum operated.
When the AIR system is enabled, vacuum is applied to the valve. |
| • | Check valves--The check valves prevent back flow of exhaust
gases into the AIR system. |
| • | 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, or 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 diagnostic trouble code (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. |
