Circuit Description

Secondary Air Injection (AIR) system is used to lower tailpipe emissions during start up. PCM supplies ground to AIR pump relay, energizing pump. PCM enables both circuits simultaneously when AIR system operation is desired. When AIR system is active, AIR pump forces fresh air into the exhaust stream to accelerate catalyst operation.

PCM runs 2 tests using HO2S voltages to diagnose AIR system. Tests consist of:

1. Test I
   
   PCM monitors HO2S voltages when AIR pump is enabled. If HO2S voltage drops to a predetermined range, PCM assumes that AIR pump is operational. If HO2S voltage increases to a predetermined range, PCM assumes that AIR pump is disabled. If HO2S voltages are out of range or inconclusive, diagnostic will proceed to next test.
2. Test II
   
   During this test, PCM will activate AIR pump during "closed loop" operation. When AIR is activated, PCM will monitor HO2S voltages and short term trim values for both banks of engine. If PCM determines that HO2S voltages for both banks does not respond as expected during tests, DTC P0410 will set. If only one sensor responded, PCM will set either a DTC P1415 or P1416 to indicate which bank AIR system is inoperative.

DTC will set when the following conditions are present:

TEST I

• DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0300, P0412, P0418, P0442, P0443, P1441 or any HO2S DTCs not set.
• Engine operating for more than 3 seconds.
• Engine load less than 80 percent.
• Engine airflow less than 35 gm/s.
• Ignition voltage greater than 11.5 volts.
• Air fuel ratio greater than 13:1.
• ECT less than 104°F (40°C).
• IAT greater than 50°F (10°C).
• HO2S voltage does not drop to less than 300 mV for 25 seconds during pump operation.
• HO2S voltage does not got greater than 600 mV for 15 seconds after pump operation is turned off.
• Power enrichment, deceleration fuel cut-off, or catalyst over-temperature not active.
• AIR system is enabled for 50 seconds (60 seconds on hot starts).

TEST II

• DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0300, P0412, P0418, P0442, P0443, P1441 or any HO2S DTCs not set.
• Engine operating greater than 5 minutes.
• Engine speed greater than 400 RPM.
• EVAP purge active.
• Maximum airflow is 35 gallons per second.
• Ignition voltage greater than 11.5 volts.
• Engine load less than 80 percent.
• Fuel system operating in closed-loop.
• This test will fail if HO2S voltage is greater than 300 mV for 4 seconds during pump operation.