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 provides an overview of each diagnostic category.

### DTC Descriptor

DTC P2431: Secondary Air Injection (AIR) System Pressure Sensor Performance
DTC P2432: Secondary Air Injection (AIR) System Pressure Sensor Circuit Low Voltage
DTC P2433: Secondary Air Injection (AIR) System Pressure Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5 V Reference | P0642 | P0641 | P0643 | P2431
AIR Pressure Sensor Signal | P2432 | P2432 | P2433 | P2431
Low Reference | -- | P2433 | -- | P2431

### Circuit/System Description

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The electric air pump forces fresh air into the exhaust stream in order to accelerate the catalyst operation. A secondary air injection pressure sensor is used to monitor the air flow from the AIR pump. The engine control module (ECM) supplies 5 volts to the 5 V reference circuit and supplies a ground to the low reference circuit. The sensor provides a signal voltage to the ECM relative to the pressure changes within the AIR system.

### Conditions for Running the DTC

#### DTC P2231

• | TBD

• | TBD

### Conditions for Setting the DTC

#### DTC P2231

• | The ECM determines that the difference between the AIR pressure sensor and the BARO sensor signals is greater than XX kPa when the AIR pump is commanded OFF.

| OR

• | The ECM determines that the difference between the AIR pressure sensor and the BARO sensor signals is greater than XX kPa when the AIR pump is commanded ON.

#### DTC P2232

The pressure sensor signal is less than 0.2 volt for at least 12.5 seconds.

#### DTC P2233

The pressure sensor signal is more than 4.8 volts for at least 12.5 seconds.

### Action Taken When the DTC Sets

DTCs P2431, P2432 and P2433 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P2431, P2432 and P2433 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Secondary Air Injection System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the diagnostic trouble code (DTC) information with a scan tool. Verify that DTCs P0641, P0642, P0643, P2227, P2228, or P2229 are not set.

⇒ | If any of the above DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Observe the scan tool Secondary Air Injection Pressure Sensor voltage parameter. The reading should be between XX-XX V.
3. Compare the scan tool BARO pressure parameter to the Altitude Versus Barometric Pressure table. The BARO should be within the specified range displayed in the table for the specific altitude.

⇒ | If not within the specified range, refer to DTC P2227, P2228, or P2229 for further diagnosis.

4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B157 secondary air injection pressure sensor.
2. Ignition OFF, remove the fuse that supplies B+ to circuit terminal 56 X2 of the ECM.
3. Test for less than 5 Ω between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

4. Install the fuse that supplies B+ to circuit terminal 56 X2 of the ECM.
5. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.

⇒ | If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

⇒ | If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

6. Verify the scan tool Secondary Air Injection Pressure Sensor voltage parameter is less than 0.5 V.

⇒ | If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the K20 ECM.

7. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 1. Verify the scan tool Secondary Air Injection Pressure Sensor voltage parameter is greater than 4.8 V.

⇒ | If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

8. If all circuits test normal, test or replace the B157 secondary air injection pressure sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Secondary Air Injection Pressure Sensor

• | Control Module References for engine control module replacement, setup, and programming