For 1990-2009 cars
Engine Controls Components
Power, Ground, A/C Compressor Clutch, and AIR
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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:

1. DTC P0412 AIR Solenoid Valve Control Circuit and P0418 AIR Pump Relay Control Circuit should be diagnosed first if either are set.

2. This step begins testing for a short to ground in the AIR pump feed circuit.

3. Listen for a running motor, command both the ON and OFF states. Repeat the commands as necessary.

4. This step begins testing for a short to voltage in the pump feed circuit.

5. This step tests for voltage at the AIR pump relay switch feed circuit.

6. This step bypasses the relay.

7. This step tests for voltage on the AIR pump feed circuit.

8. This step tests for an open on the pump ground circuit.

9. 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? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are DTCs P0412 or P0418 set? | -- | Go to Diagnostic Trouble Code (DTC) List/Type | Go to Step 3
3 | Is the AIR pump relay switch feed fuse OK? | -- | Go to Step 4 | Go to Step 14
4 | With a scan tool, command the AIR pump ON and OFF. Does the AIR pump turn ON and OFF with each command? | -- | Go to Step 11 | Go to Step 5
5 | Does the AIR pump run continuously? | -- | Go to Step 17 | Go to Step 6
6 |

1. Disconnect the AIR pump relay.
2. Probe the relay switch feed circuit using a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 18

7 | With a fused jumper wire, jumper the relay switch feed circuit to the AIR pump feed circuit. Does the AIR pump operate? | -- | Go to Step 8 | Go to Step 9
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? | -- | Go to Step 30 | Go to Step 25
9 |

1. Leave the fused jumper in place.
2. Disconnect the AIR pump.
3. Probe the feed circuit of the pump with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 19

10 | Connect a test lamp between the feed circuit of the pump and the ground circuit of the pump. Does the test lamp illuminate? | -- | Go to Step 28 | Go to Step 20
11 |

1. Disconnect the AIR hose/pipe from the AIR pump.
2. With a scan tool, command the AIR pump ON.

Is air flow present at the AIR pump outlet?

--

Go to Step 12

Go to Step 29

12 |

1. Reconnect the AIR hose/pipe to the AIR pump.
2. Disconnect the AIR hose/pipe from the AIR combination valve.
3. With a scan tool, command the AIR pump ON.

Is air flow present at the AIR hose/pipe outlet?

--

Go to Step 13

Go to Step 23

13 | Visually inspect the following:

• | With the engine running, test for engine vacuum at the AIR combination valve. If vacuum is not present, inspect for a damaged, pinched, or disconnected vacuum line, a blocked/restricted vacuum port, or a faulty vacuum control solenoid valve.

• | Inspect for a damaged, pinched, or disconnected vacuum line between the vacuum control solenoid and the combination valves.

• | Inspect for a short to voltage on the AIR Solenoid Valve Control circuit.

Did you find and correct the condition?

--

Go to Step 24

Go to Step 27

14 |

1. Disconnect the AIR pump relay. Refer to Secondary Air Injection Pump Relay Replacement .
2. Test the feed circuit of the relay switch for a short to ground.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 15

15 |

1. Disconnect the AIR pump. Refer to Secondary Air Injection Pump Relay Replacement .
2. Test the feed circuit of the pump for a short to ground.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 16

16 |

1. Reconnect the relay.
2. Reconnect the AIR pump.
3. Install a new fuse.
4. With a scan tool, command the AIR pump ON.

Does the fuse open?

--

Go to Step 29

Go to Diagnostic Aids

17 | Disconnect the AIR pump relay. Is the pump still running? | -- | Go to Step 25 | Go to Step 26
18 | Repair the open relay switch feed circuit. Refer to Wiring Repairs in Wiring Systems . Did you complete the repair? | -- | Go to Step 30 | --
19 |

1. Test for an open in the AIR pump feed circuit.
2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 30

Go to Step 26

20 | Repair the open/high resistance in the AIR pump ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 30 | --
21 | Repair the short to ground in the relay switch feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 30 | --
22 | Repair the short to ground in the AIR pump feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 30 | --
23 | Visually inspect the following and repair as necessary:

• | A blocked or damaged combination valve

• | A restriction, blockage, disconnect, or other damage to the AIR hoses/pipes from the combination valve to the exhaust system

Did you complete the repair?

--

Go to Step 30

--

24 | Repair the vacuum system as necessary. Did you complete the repair? | -- | Go to Step 30 | --
25 | Repair the short to voltage in the AIR pump feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 30 | --
26 | Replace the AIR pump relay. Refer to Secondary Air Injection Pump Relay Replacement . Did you complete the replacement? | -- | Go to Step 30 | --
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? | -- | Go to Step 30 | --
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? | -- | Go to Step 30 | Go to Step 29
29 | Replace the AIR pump. Refer to Secondary Air Injection Pump Replacement . Did you complete the replacement? | -- | Go to Step 30 | --
30 |

1. With a scan tool, clear the DTCs.
2. Turn OFF the ignition and wait 15 seconds.
3. Operate the vehicle within the conditions that are required for this diagnostic to run. Refer to Conditions for Running the DTC.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 31

Go to Step 2

31 | With a scan tool, review Captured Info. Are there any DTCs that have not been diagnosed? | -- | Go to applicable DTC table | System OK