DTC Descriptor
DTC P0418 : Secondary Air Injection (AIR) Pump Control CircuitDiagnostic Fault Information
Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
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 | P2444 | -- |
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
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:
- DTCs P0411 and P2430 run during Phase 1
- DTCs P2430 and P2440 run during Phase 2
- 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 P0418 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The actual and expected states of the AIR Pump Relay Control Circuit do not match. |
| • | The condition exists for at least 2 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
With the ignition ON and the engine OFF, enable and disable the AIR pump with a scan tool while observing that the pump relay operates.
| ⇒ | If the pump relay does not operate then proceed with Circuit/System Testing. |
Circuit/System Testing
- With the ignition ON, the engine OFF, and the pump enabled with a scan tool, observe the relay and the pump while manipulating all related wiring and connectors.
- With the ignition ON, the engine OFF, and the pump relay removed, connect a test lamp from the relay coil voltage supply circuit to ground and observe that the lamp illuminates.
- With the ignition ON, the engine OFF, and the pump relay removed, connect a test lamp from the relay coil voltage supply circuit to the relay control circuit and observe that the lamp does not illuminate.
- With the ignition ON, the engine OFF, the pump relay removed, a test lamp connected from the relay coil voltage supply circuit to the relay control circuit, and the AIR pump enabled with a scan tool, observe that the test lamp illuminates.
- If all circuits and the control module are OK then replace the pump relay.
| ⇒ | If manipulation does affect the relay or the pump then repair the harness or connector. |
| ⇒ | If the lamp does not illuminate then test the voltage supply circuit for high resistance or a short to ground. |
| ⇒ | If the lamp illuminates then test the control circuit for a short to ground or a faulty control module. |
| ⇒ | If the lamp does not illuminate then test the relay control circuit for high resistance, a short to voltage, or a faulty control module. |
Component Testing
Connect the relay coil connections to fused battery voltage and ground. Measure resistance through the relay contacts at 0 ohms.
| ⇒ | If resistance measures more than 0 ohms then replace the relay. |
Repair Instructions
Control Module References for control module replacement and programming.
Repair Verification
With the ignition ON and the engine OFF, enable and disable the AIR pump with a scan tool while observing that the pump relay operates.
