Circuit Description
An AIR pump is used on this vehicle in order to lower the tail pipe emissions on start-up. The powertrain control module (PCM) grounds the AIR pump relay control circuit, which energizes the AIR pump. The PCM also grounds the AIR combination valve vacuum control circuit, which energizes the AIR vacuum solenoid valve. Vacuum is then applied to both AIR combination valve diaphragms which open the shut-off valves. The PCM enables both circuits simultaneously when AIR system operation is desired. When the AIR system is active, the AIR pump forces fresh air into the exhaust stream in order to accelerate catalyst operation. The AIR solenoid valves replace the conventional check valves. When the AIR system is inactive the shut-off valves prevent air flow in either direction. DTC P0412 applies to the AIR vacuum control solenoid circuit. DTC P0418 applies to the AIR pump relay control circuit. DTC P0410 sets if an air flow problem is detected.
The PCM will run up to 3 diagnostic tests using the HO2S 1 voltage to diagnose the AIR system. The first is a passive test, it has 2 parts. The 2 parts are the AIR Passive Test 1, and AIR Passive Test 2. The second test is an Active Test, it has one part. This test is named AIR Active Test.
The AIR Passive/Active Tests consist of the following:
AIR Passive Test 1
| • | When the AIR system is enabled, the PCM monitors the HO2S 1 voltage for a specific amount of time calculated by the coolant temperature at start-up. The HO2S 1 is monitored for 10 seconds if the coolant temperature is more than 90°C (194°F), or 70 seconds if the coolant temperature is less than 90°C (194°F). |
| • | If the HO2S 1 voltage goes below a calibrated amount, the PCM interprets this as an indication the AIR System is operational and it is considered a test passed. |
| • | When the AIR Passive Test 1 completes, the PCM then runs the AIR Passive Test 2. |
AIR Passive Test 2
| • | When the AIR System is disabled, the PCM monitors the HO2S 1 voltage. The HO2S 1 voltage should increase above a calibrated amount and switch normally. |
| • | When the AIR Passive Test 2 is complete and both AIR Passive tests indicate a pass, no further action is taken. If either one of the above tests have failed or is inconclusive, the diagnostic will proceed to the AIR Active Test. |
AIR Active Test
| • | During this test the PCM turns the AIR system on during Closed Loop operation. When the AIR system is activated, the PCM monitors the HO2S voltage. If the AIR system is operating properly, the HO2S 1 voltage should go below a predetermined level. |
| • | The PCM will repeat this test up to 3 consecutive times with a short delay between each command. |
| • | If the PCM determines that the HO2S 1 voltage did not respond as expected during the tests, DTC P0410 will set. |
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0300, P0412, P0418, P0442, P0443, P1441, and HO2S are not set. |
| • | The engine operates for more than 2 seconds. |
Condition For Not Passing AIR Active Test
The HO2S 1 voltage changes less than .06 or is more than 225 mV for 1.5 seconds during 2.5 seconds of AIR pump operation.
Conditions for Setting the DTC
| • | The pre-catalyst HO2S voltage remains above 300 mV (Passive) or 150 mV (Active) for a calibrated period of time. |
| AND |
| • | The Short Term FT does not increase a calibrated amount during the test. |
| • | Both the above conditions exist for 3 consecutive tests. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
Inspect for the following:
Important: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Faulty terminal connection--Inspect the harness connectors for the following conditions: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Faulty terminal to wire connection--Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. |
| • | Damaged harness--Inspect the wiring harness for damage. |
| If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. |
| • | Clean and secure connections at the PCM and the engine grounds. |
If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
DTC P0412 AIR Solenoid Valve Control Circuit and P0418 AIR Pump Relay Control Circuit should be diagnosed first if either are set.
-
This step begins testing for a short to ground in the AIR pump feed circuit.
-
Listen for a running motor, command both the ON and OFF states. Repeat the commands as necessary.
-
This step begins testing for a short to voltage in the pump feed circuit.
-
This step tests for voltage at the AIR pump relay switch feed circuit.
-
This step bypasses the relay.
-
This step tests for voltage on the AIR pump feed circuit.
-
This step tests for an open on the pump ground circuit.
-
The AIR Pump is not designed to run continuously. If the pump needs to be replaced, inspect for conditions that may cause continuous pump operation.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||
Are DTCs P0412 or P0418 set? | -- | |||||||||
Is the AIR pump relay switch feed fuse OK? | -- | |||||||||
With a scan tool, command the AIR pump ON and OFF. Does the AIR pump turn ON and OFF with each command? | -- | |||||||||
Does the AIR pump run continuously? | -- | |||||||||
Does the test lamp illuminate? | -- | |||||||||
With a fused jumper wire, jumper the relay switch feed circuit to the AIR pump feed circuit. Does the AIR pump operate? | -- | |||||||||
8 | Inspect the AIR Pump Relay Control circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
Does the test lamp illuminate? | -- | |||||||||
Connect a test lamp between the feed circuit of the pump and the ground circuit of the pump. Does the test lamp illuminate? | -- | |||||||||
11 |
Is air flow present at the AIR pump outlet? | -- | ||||||||
12 |
Is air flow present at the AIR hose/pipe outlet? | -- | ||||||||
13 | Visually inspect the following:
Did you find and correct the condition? | -- | ||||||||
14 |
Did you find and correct the condition? | -- | ||||||||
15 |
Did you find and correct the condition? | -- | ||||||||
16 |
Does the fuse open? | -- | Go to Diagnostic Aids | |||||||
17 | Disconnect the AIR pump relay. Is the pump still running? | -- | ||||||||
18 | Repair the open relay switch feed circuit. Refer to Wiring Repairs in Wiring Systems . Did you complete the repair? | -- | -- | |||||||
19 |
Did you find and correct the condition? | -- | ||||||||
20 | Repair the open/high resistance in the AIR pump ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
21 | Repair the short to ground in the relay switch feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
22 | Repair the short to ground in the AIR pump feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
23 | Visually inspect the following and repair as necessary:
Did you complete the repair? | -- | -- | |||||||
24 | Repair the vacuum system as necessary. Did you complete the repair? | -- | -- | |||||||
25 | Repair the short to voltage in the AIR pump feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
26 | Replace the AIR pump relay. Refer to Secondary Air Injection Pump Relay Replacement . Did you complete the replacement? | -- | -- | |||||||
27 | Replace the affected AIR combination valve. Refer to Secondary Air Injection Check Valve and Check Valve Pipe Replacement - Bank 2 , or Secondary Air Injection Check Valve and Check Valve Pipe Replacement - Bank 1 . Did you complete the replacement? | -- | -- | |||||||
28 | Test for faulty connections at the AIR pump. Refer to Testing for Intermittent Conditions and Poor Connections . Did you find and correct the condition? | -- | ||||||||
Replace the AIR pump. Refer to Secondary Air Injection Pump Replacement . Did you complete the replacement? | -- | -- | ||||||||
30 |
Does the scan tool indicate that this test ran and passed? | -- | ||||||||
31 | With a scan tool, review Captured Info. Are there any DTCs that have not been diagnosed? | -- | Go to applicable DTC table
| System OK |
