• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Pressure Sensor 5-Volt Reference Voltage | P2432 | P2432 | 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 | -- | -- |
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 |
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 powertrain control module (PCM) 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:
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 barometric pressure (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 PCM 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.
• | The system voltage is between 9-18 volts. |
• | This DTC runs on a 100 ms loop. |
• | DTC P0418 runs continuously when the above conditions are met. |
• | The actual and expected states of the AIR pump relay control circuit do not match. |
• | The condition exists for at least 2 seconds. |
DTC P0418 is a type B DTC.
DTC P0418 is a type B DTC.
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Ignition ON, enable and disable the AIR pump with a scan tool while observing that the AIR pump relay operates.
⇒ | If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the PCM. |
⇒ | 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 PCM. |
⇒ | If the pump does not activate, test the pump voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the pump. |
⇒ | If the pump 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 or test all connected components and replace as necessary. |
⇒ | If the test lamp does not illuminate, test the affected relay coil voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open or test all connected components and replace as necessary. |
Control Module References for control module replacement and programming
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.