Circuit Description
The purpose of the Secondary Air Injection (AIR) system is to reduce Hydrocarbon (HC), the Carbon Monoxide (CO), and the Oxides of Nitrogen (NOx) exhaust emissions by causing any combustible gases in the exhaust to re-burn. This also causes the catalytic converters and the heated oxygen sensors to reach the normal operating temperatures more quickly, thus Closed Loop operation occurs earlier.
When the engine is started, the ECM commands the AIR pump relay and the AIR Cutoff 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 Cutoff 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 Cutoff Valve Vacuum Control solenoid. A check valve close to the engine prevents hot exhaust gases from backing up into the AIR system.
The ECM uses the Short Term Fuel Trim in order to diagnose the AIR system. When the AIR system is enabled, the ECM monitors the Short Term Fuel Trim. If the Short Term Fuel Trim goes below a threshold, the ECM interprets this as an indication that the AIR system is operational. When the AIR pump is disabled, the Short Term Fuel Trim should return to normal.
Conditions for Running the DTC
| • | One or more of the following DTCs are not set: P0100, P0110, P0115, P0116, P0120, P0133, P0153, P0171, P0172, P0174, P0175, P0300 thru P0306, P0560, P0440, P0441, or P0443. |
| • | The Closed Loop is enabled |
| • | The EVAP purge disabled. |
| • | The IAT is greater than 5.3°C (41.5°F). |
| • | The ECT is greater than 18.8°C (65.8°F). |
| • | The engine is at idle. |
| • | Vehicle speed=0 miles/h. |
| • | The short term fuel trim is above the minimum limit of approximately -25%. |
| • | The start up ECT is between 0° and 36°C (32° and 97.0°F). |
Conditions for Setting the DTC
The Short term fuel trim remains below a predetermined value for at least 20 seconds.
Action Taken When the DTC Sets
The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes. |
| • | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The ECM battery voltage is interrupted. |
| • | The scan tool clears the MIL/DTC. |
Diagnostic Aids
| • | Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals. |
| • | Check the AIR system for an intermittent problem. Check for the following conditions: |
| - | An intermittent short to B+ on the pump feed circuit. |
| - | Sticking relay contacts |
| - | A sticking AIR cutoff valve |
Refer to Symptoms for the Intermittents.
Test Description
The number(s) below refer to the step numbers on the diagnostic table.
-
At start up, the ECM may be commanding the AIR pump on if the conditions are appropriate. Let the engine run long enough in order to enter a Closed Loop operation.
-
Inspect the check valve. Check the hoses after the check valve for evidence of heat damage. A heat damaged hose indicates that the check valve is stuck open, allowing exhaust gas back into the AIR system, and allowing the outside air to be drawn into the exhaust stream.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | ||||||||
Does the AIR pump turn ON and OFF? | -- | |||||||||
3 | Remove the AIR pump relay. Is the AIR pump OFF? | -- | ||||||||
4 |
Does the test lamp turn ON and OFF? | -- | ||||||||
5 |
Is the test lamp illuminated? | -- | ||||||||
6 |
Is the valve stuck open? | -- | ||||||||
7 |
Is a vacuum present when the solenoid valve is OFF? | -- | ||||||||
8 | Inspect for the following:
Did you find and correct the condition? | -- | Refer to Diagnostic Aids | |||||||
9 | Repair the AIR pump feed circuit between the AIR pump and the AIR pump relay shorted to B+. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
10 | Repair the relay control circuit shorted to ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
11 | Replace the relay. Is the repair completed? | -- | -- | |||||||
12 | Replace the secondary AIR cutoff valve vacuum solenoid. Refer to Secondary Air Cutoff Valve Vacuum Solenoid Replacement . Is the action complete? | -- | -- | |||||||
13 | Replace the AIR cutoff valve. Refer to Secondary Air Injection Cut Off Valve Replacement . Is the action complete? | -- | -- | |||||||
14 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |||||||
Is this DTC set? | -- | |||||||||
16 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
