P0412

CIRCUIT DESCRIPTION
The purpose of the Secondary Air Injection (AIR) system is to reduce the Hydrocarbon (HC), the Carbon Monoxide (CO), and the Oxides Of Nitrogen (NOx) exhaust emissions by causing any combustible gases in the exhaust to reburn. This also causes the catalytic converters and the Heated Oxygen (HO2S) sensors to reach the normal operating temperatures more quickly, thus the Closed Loop operation occurs earlier.

When the engine is started, the Engine Control Module (ECM) commands the AIR pump relay and the AIR cut-off valve vacuum control solenoid ON, injecting clean air into the engine exhaust ports. The ECM switches the AIR system OFF when the oxygen sensors become active. The AIR cut-off valve prevents air from being drawn into the system when the AIR pump is OFF. The vacuum to the valve is controlled by the AIR cut-off valve vacuum control solenoid. A check valve close to the engine prevents hot exhaust gases from backing up into the AIR system.

The secondary air injection solenoid receives switched battery power from the engine controls power relay. The ECM controls the solenoid by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM commands a component ON, the voltage of the control circuit should be low, near 0 volts. When the ECM commands a component OFF, the voltage potential of the control circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this Diagnostic Trouble Code (DTC) will set.

CONDITIONS FOR RUNNING THE DTC
^ The engine speed is more than 40 RPM.
^ The battery voltage is between 7.5-15 volts.
^ The above conditions are present for 300 ms (0.3 seconds).

CONDITIONS FOR SETTING THE DTC
A short to ground, an open circuit, or a short to battery voltage detected on the control circuit

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
Use the J 35616-A Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

Check for the following conditions:
^ Poor connections at the ECM or at the component-Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Damaged harness-Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault.

Refer to Intermittent Conditions for the intermittents. Intermittent Conditions

TEST DESCRIPTION

Steps 1-8:

Steps 9-18:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the solenoid operates. Repeat the commands as necessary.
3. This check can detect a partially shorted solenoid coil which would cause an excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm, the coil may open, the amps drop to 0, or short, go to above 0.20 amp.
15. Perform the Idle Learn Procedure when replacing the ECM or the throttle body.