P0438 Diagnostic Trouble Code

P0438 is a kind of OBD-II Diagnostic P-Powertrain Diagnostic Trouble Code.

It is considered generic because it applies to all makes and models of vehicles, although specific repair steps may be different depending on your car model.

Symptoms

Symptoms of a P0438 diagnostic trouble code may include:

Lack of power
Faulty O2 Sensor
Poor acceleration
If the DPF is not cleared the ECU will revert to the "Limp Home Mode" until the situation is corrected

Possible Causes :

A large air leak at or near the number one oxygen sensor would also cause a lean mixture.
Faulty IMRC actuator relay (if equipped)
Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0307 for number 7.

Repair Processes :

You might continue by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio.

Process Tips

Diagnostic trouble code P0438 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before P0438.

Fortunately, P0438 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.

P0438 Trouble Code For Specific Cars

P0438 Mazda Familia Trunk Key Cylinder Switch Failure
P0438 Volkswagen Type 4 SCP (J1850) Invalid or Missing Data for Brakes
P0438 Bmw 420 Child Seat Detection Circuit Short to Ground
P0438 Peugeot Expert Enable Signal Circuit Short to Battery
P0438 Porsche 962 Fuel Level Sensor B Intermittent/Bypass Line Monitor
P0438 Venturi Cabriolet Purge flow Sensor Circuit High Input
P0438 Marmon V16 Transmission 4-Wheel Drive Mode Select Circuit Failure