Pulsed Secondary Air Injection System Diagnostics

The pulsed secondary air injection system reduces the emission of hydrocarbons (HC) and carbon dioxide (CO) and heats the catalytic convener more rapidly. When the engine is started from cold the pulsed secondary air injection system (PAIR) introduces fresh air (oxygen) into the exhaust manifold in order to promote afterburning (oxidation) of hydrocarbons and carbon monoxide. This makes it possible to increase injection period and retard ignition, increasing exhaust temperature and activating the catalytic convener more quickly. If the pulsed secondary air injection system is not working exhaust emissions will increase when cold-starting and possibly during normal driving. To avoid this the engine control module monitors the pulsed secondary air injection system.

The diagnostic test is divided into phases in which the various components are tested, if a fault is detected the diagnostic test is interrupted and a diagnostic trouble code is stored for that component. The main principle of the diagnostic is to interfere with long term fuel trim using the pulsed secondary air injection system and study the behavior of the integrator.

1. Long-term fuel trim idling and partial load is blocked and canister purge (CP) valve control is stopped. The engine control module starts by checking what the integrator is doing. If the integrator is at maximum the pulsed secondary air injection system pump is operating continuously and the pulsed secondary air injection system valve is leaking, diagnostic trouble code EFI-42 Pulsed secondary air injection system, EFI-46 Pulsed secondary air injection system valve and EFI-448 Pulsed secondary air injection system pump will be stored.

2. The pulsed secondary air injection system pump is started and the pulsed secondary air injection system pump is kept closed. The integrator should remain unchanged, if it rises above a certain limit within 7 seconds this indicates a leaking pulsed secondary air injection system valve and diagnostic trouble code EFI-46 Pulsed secondary air injection system valve is stored (MAX FAULT).

3. The pulsed secondary air injection system valve is opened and the pulsed secondary air injection system pump continues to operate. The integrator should now rise above a certain limit within 7 seconds, if this does not occur this indicates that the pulsed secondary air injection system pump is not operating or that the pulsed secondary air injection valve has not opened, diagnostic trouble code EFI-445 Pulsed secondary air injection system pump is stored (MIN FAULT).

4. The pulsed secondary air injection system pump is shut down, the pulsed secondary air injection system valve is closed and long-term fuel trim idling and part load are released. The diagnostic test is completed.

To carry out the diagnostic:

^ Engine temperature must be between -10 - +40°C (+14 - +104°F) when the engine is started.
^ No permanent faults must be stored for the throttle position (TP) sensor, either of the heated oxygen sensors, the canister purge valve, battery voltage, fuel trim, the pulsed secondary air injection solenoid, pulsed secondary air injection pump and the engine must not be misfiring.
^ Engine idling.
^ Speed lower than 4 km/h (2.4 mph).
^ The integrator must not be at minimum.
^ Engine coolant temperature (ECT) must not exceed 95°C (203°F).

The diagnostic test will not start until 10 minutes after the engine has been started when all conditions have been fulfilled, it then takes a maximum of 20 seconds. If the diagnostic is interrupted it will try again the next time all conditions are met, but not until 11 minutes have passed since the previous attempt. The engine control module makes a maximum of 3 attempts in one journey, if the diagnostic test is interrupted all three times it will not try again until the engine is started again.