Technical Description of OBD-II Trouble Code
The circuit for the air flow/pressure sensor in the secondary air injection system is detecting high levels of pressure in Bank 2.
What does that mean?
This is a generic diagnostic trouble code (DTC) that applies to many OBD-II vehicles (1996-newer). This includes vehicles from various manufacturers such as Buick, Chevrolet, Cadillac, Lexus, Toyota, BMW, Subaru, etc. The exact repair steps may vary depending on the year, make, model, and powertrain configuration.
OBD-II trouble code P2438 and related codes P2435, P2436, P2437, and P2439 are associated with the air flow/pressure sensor circuit in the secondary air injection system of Bank 2. Bank 2 refers to the side of the engine that does not contain cylinder #1.
The purpose of the air flow/pressure sensor circuit in the secondary air injection system of Bank 2 is to reduce hydrocarbon exhaust emissions during engine start-up in cold weather conditions. The Power Control Module (PCM) activates the air pump to supply pressurized fresh air, which helps accelerate the catalyst operation and reduce harmful exhaust gas levels. This process also helps the engine reach its normal operating temperature faster. The air system pressure sensor monitors the pressure at the air control solenoid valve inlet and opens or closes the valve based on predetermined temperatures and pressures recommended by the manufacturers.
When the PCM detects voltage or resistance that is significantly higher than the normal expected range in the air flow/pressure sensor circuit of Bank 2, it sets code P2438 and may illuminate the check engine light.
Components of the secondary air injection system:
What is the severity of this DTC?
The severity of this code can vary from moderate to severe depending on the specific symptoms of the malfunction. Several symptoms associated with this trouble code can make driving the vehicle extremely hazardous.
What are some of the symptoms of the code?
Symptoms of a P2438 trouble code may include:
What are some of the common causes of the code?
Causes for this P2438 code may include:
What are some P2438 troubleshooting steps?
The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins (TSB’s) for the specific vehicle based on its year, model, and power plant. This can save a lot of time in the long run by providing guidance in the right direction.
Based on the specific vehicle, this circuit may incorporate several components including the secondary air injection pump, check valve, pressure sensor, air control valve, and the PCM. Perform a thorough visual inspection to check the associated wiring for any obvious defects such as scraping, rubbing, bare wires, or burn spots. Next, check the connectors and connections for security, corrosion, and damaged pins. This process should include all wiring connectors and connections to all components, including the PCM. Consult the specific technical data for the vehicle to verify the circuit configuration and confirm every component incorporated within the circuit, which may include a fuse or a fuse-able link. Test the check valve to ensure that the airflow is in one direction only. If ice forms in the secondary air injection pump during extremely cold weather conditions, it indicates a defective one-way check valve that is allowing condensation from the exhaust to enter the pump.
Advanced Steps
The advanced steps are highly specific to the vehicle and require advanced equipment to perform accurately. These procedures involve using a digital multimeter and referring to the specific technical references for the vehicle.
Voltage Checks
The reference voltage and acceptable ranges may vary based on the specific vehicle and circuit configuration. The specific technical data will include troubleshooting charts and the appropriate sequence to follow for an accurate diagnosis.
If this process identifies the absence of a power source or ground, continuity testing may be required to check the integrity of the wiring, connectors, and other components. Continuity tests should always be performed with the power removed from the circuit, and the normal readings for wiring and connections should be 0 ohms of resistance. Resistance or no continuity indicates faulty wiring that is open, shorted, or corroded and must be repaired or replaced.
What are some common repairs for this code?
Common Mistake
We always recommend seeking professional service to mechanically solve this issue. However, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to be addressed. If you are interested in this option, please upload your ECU file to our portal.
