P2438 indicates the engine control module has detected an abnormally high voltage signal from the secondary air injection system’s air flow/pressure sensor on bank 2. This usually means the sensor or its circuit is reporting excessive pressure or flow when little or none is present.
The sensor itself may have an internal short to voltage or a failed sensing element, causing it to report high pressure continuously.
Wiring between the sensor and PCM may be shorted to power, or connectors may be corroded, bent, or loose, causing a high-voltage signal.
A blocked air injection passage, check valve, or pump outlet can cause abnormally high back-pressure, which the sensor may interpret as a high flow condition.
A failing pump may operate erratically or create excessive pressure, leading the sensor to report high values.
A stuck-open check valve can allow exhaust gases to enter the air injection system, increasing pressure and triggering the sensor.
While uncommon, a PCM software error or internal short could cause a false high-voltage reading, but this is a last-resort diagnosis after all other causes are ruled out.
No. The PCM is rarely the cause of this code. Most cases stem from a faulty sensor, wiring issues, or problems in the secondary air injection system itself. Replace the PCM only after all other potential causes have been thoroughly tested and ruled out.
While the vehicle may still be drivable, prolonged driving with this code can lead to reduced fuel economy, potential damage to the secondary air injection system, or failure of emissions tests. It’s best to diagnose and repair the issue promptly.
The pressure sensor monitors the flow and pressure of air being injected into the exhaust system to ensure proper operation. This helps the PCM verify that the system is functioning correctly for emissions control and catalyst protection.
Disconnecting the battery may temporarily clear the code, but it will likely return if the underlying issue is not addressed. Clearing codes without diagnosis can also erase valuable freeze-frame data needed for troubleshooting.