For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### DTC Descriptors

DTC P0412 : Secondary Air Injection (AIR) Solenoid Control Circuit
DTC P0418 : Secondary Air Injection (AIR) Pump Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Pressure Sensor 5-Volt Reference Voltage | P2432 | P2431 | P2431 | P2430, P2431
Pressure Sensor Signal | P2432 | P2432 | P2433 | P2430, P2431
Pressure Sensor Low Reference | -- | P2433 | -- | --
Pump Voltage Supply | P0411 | P0411 | 2444 | --
Pump Ground | -- | P0411 | -- | --
Solenoid Voltage Supply | P0411 | P0411 | P2440 | --
Solenoid Ground | -- | P0411 | -- | --
Pump Relay Coil Voltage Supply | P0411, P0418 | P0411, P0418 | -- | --
Pump Relay Coil Control | P0418, P2444 | P0411, P0418 | P0418 | --
Pump Relay Switch Supply | P0411 | P0411 | -- | --
Solenoid Relay Coil Voltage Supply | P0411, P0412 | P0411, P0412 | -- | --
Solenoid Relay Coil Control | P0412, P2440 | P0411, P0412 | P0412 | --
Solenoid Relay Switch Supply | P0411 | P0411 | -- | --

### Typical Scan Tool Data

#### AIR Pressure Sensor

Circuit | Normal Range | Short to Ground | Open | Short to Voltage
--- | --- | --- | --- | ---
Operating Conditions: Key ON, Engine OFF
5-Volt Reference Voltage | BARO | 41 kPa | 41 kPa | 111 kPa
Pressure Sensor Signal | BARO | 42 kPa | 41 kPa | 150 kPa
Low Reference | BARO | BARO | 145 kPa | BARO

### Circuit/System Description

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the secondary AIR injection pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The control module supplies the internal pressure sensor with a 5-volt reference, an electrical ground, and a signal circuit.

The AIR diagnostic uses 3 phases to test the AIR system:

1. DTCs P0411 and P2430 run during Phase 1
2. DTCs P2430 and P2440 run during Phase 2
3. DTC P2444 runs during Phase 3

During phase 1, both the AIR pump and the solenoid valve are activated. Normal secondary air function occurs. Expected system pressure is 8-10 kPa above BARO.

During phase 2, only the AIR pump is activated. The solenoid valve is closed. Pressure sensor performance and solenoid valve deactivation are tested. Expected system pressure is 20-25 kPa above BARO.

During phase 3, neither the AIR pump nor the solenoid valve is activated. AIR pump deactivation is tested. Expected system pressure equals BARO.

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The control module can detect faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly, and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

### Conditions for Running the DTC

• | The system voltage is between 9-18 volts.

• | This DTC runs on a 100 ms loop.

• | DTC P0412 and P0418 run continuously when the above conditions are met.

### Conditions for Setting the DTC

• | The actual and expected states of the AIR Solenoid Relay Control Circuit, DTC P0412, or the AIR Pump Relay Control Circuit, DTC P0418, do not match.

• | The condition exists for at least 2 seconds.

### Action Taken When the DTC Sets

DTC P0412 and P0418 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P0412 and P0418 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Controls Connector End Views

• | Engine Control Module Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Electrical Center Identification Views

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

Ignition ON, command the affected relay ON and OFF with a scan tool. Feel or listen to verify that the affected relay turns ON and OFF with each command.

### Circuit/System Testing

1. Ignition OFF, disconnect the affected relay.
2. Ignition ON, connect a test lamp between the positive terminal at the battery and the relay control circuit terminal.
3. Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒ | If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Connect an appropriately fused jumper wire between the positive voltage terminal at the battery and the load voltage supply circuit terminal and verify load activation.

⇒ | If the load does not activate, test the load voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the load.

5. Ignition ON, connect an appropriately fused jumper wire between the relay switch voltage supply circuit terminal and the load voltage supply circuit terminal and verify load activation.

⇒ | If the load does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all components connected to the fuse and replace as necessary.

6. Ignition ON, verify that a test lamp illuminates between the relay coil voltage supply circuit terminal and ground.

⇒ | If the test lamp does not illuminate, test the relay coil voltage supply circuit for a short to ground or an open/high resistance.

7. If all circuits and the ECM test normal, test or replace the affected relay.

### Component Testing

#### Relay Test

1. Test between the normally-closed switch terminals, if any, for 0 ohms.
2. Test between the normally-open switch terminals for infinite ohms.
3. Test between each switch terminal and either coil terminal for infinite ohms.
4. Connect the relay coil terminals to ground and fused power to energize the relay.
5. Test between the normally-closed switch terminals, if any, for infinite ohms.
6. Test between the normally-open switch terminals for 0 ohms.
7. Test between each switch terminal and either coil terminal for 0 volts.

### Repair Instructions

Control Module References for control module replacement, setup and programming

### Repair Verification

Ignition ON, command the relay ON and OFF with a scan tool. Feel or listen to verify that the relay turns ON and OFF with each command.