Fault code P0048 is called “Turbocharger/Supercharger Boost Control “A” Circuit High” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0048
This Diagnostic Trouble Code (DTC) is a generic powertrain code. Error P0048 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly from model to model.
Turbochargers and superchargers are air pumps that blow air into the engine to increase power. Blowers are driven from the engine’s crankshaft by a belt. And turbochargers are driven by the engine’s exhaust.
Many modern turbocharged cars use what’s called a variable geometry turbocharger (VGT). This type of turbocharger has adjustable blades located around the outside of the turbine. Which can be opened and closed to change the amount of boost pressure.
This allows the turbocharger to be controlled regardless of engine speed. Typically, the blades are closed when the engine is under light load. And they open when the load is increased.
The blade position is controlled by the powertrain control module (PCM), usually with an electronic control solenoid or motor. The position of the turbocharger is determined by a special position sensor.
On vehicles with a conventional turbocharger, the boost is regulated via a bypass valve. This valve opens to release the boost pressure. The PCM monitors this system using a boost pressure sensor.
Regarding fault code P0048, “A” indicates a problem in a part of the system circuit, not a specific symptom or component.
Code P0048 is set when the PCM detects a high signal on the boost control solenoid. Regardless of whether the engine uses a turbo VGT or a conventional turbo/charger.
Symptoms of vehicle malfunctions
The main signal that an error P0048 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the ECM memory as a malfunction).
- Increased power, resulting in detonation and possible engine damage.
The severity of code P0048, can range from medium to severe. In some cases, turbocharger/charger problems can cause serious engine damage. It is recommended that this error be corrected as soon as possible.
Factors that can cause this error code
The error code P0048 can mean that one or more of the following problems have occurred:
- Faulty turbocharger pressure sensor / turbocharger position sensor.
- Defective turbocharger / supercharger.
- Stuck bypass damper in open or closed position.
- Loose connection or damaged gasket between exhaust manifold and turbocharger.
- Control solenoid defective.
- Short-circuited or broken electrical wiring relating to the boost pressure sensor.
- Wiring problems or improper connection of electrical connector to charge pressure sensor.
- Defective PCM.
- Vacuum leaks if the valve is vacuum controlled.
How to fix or reset OBD-2 code P0048
Some suggested steps for troubleshooting and fix the error code P0048:
- Start by checking the electrical circuit. To do this, check for power and ground at the solenoid. The solenoid should be commanded to energize with a diagnostic tool when making these checks. If there is no power or ground, refer to the factory wiring diagram to determine the cause.
- After that, check the turbocharger / supercharger. Remove the air intake to check the turbocharger / blower for damage or debris. If damage is found, replace the unit.
- Check the position/pressure sensor and circuit. In most cases, there should be three wires (power, ground and signal) running to the position sensor. Make sure all three wires are present.
- Test the control solenoid. In some cases, you can test the solenoid by checking its internal resistance with an ohmmeter. For specific data, it is worth referring to the factory repair information. You can also connect the solenoid to power and ground to see if it works.
Diagnose and repair of problems
Start by visually inspecting the turbocharger control system. Look for loose connections, damaged wiring, vacuum leaks, etc. Then check the service bulletins (TSB) for the problem P0048. If nothing is found, you will need to move on to step-by-step system diagnostics.
The following describes a generalized procedure, as testing this code varies from vehicle to vehicle. To check the system accurately, you will need to refer to the manufacturer’s diagnostic block diagram.
Check the operation of the system by instructing the control solenoid to change position with the diagnostic tool. Raise the engine speed to approximately 1200 rpm. Toggle the solenoid between on and off.
The engine RPM should change and the position of the PID sensor on the diagnostic tool should also change. If the RPM fluctuates, but the PID position/pressure control does not change, the problem is in the sensor or its circuit.
If the RPM does not change, the problem is with the control solenoid, turbocharger / supercharger, or wiring.
On which vehicles does this problem occur most frequently
Fault code P0048 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Audi (A6)
- Chevrolet
- Chrysler
- Dodge (Caravan)
- Ford (F-150, Transit)
- Jeep
- Land Rover
- Mazda
- Toyota (Land Cruiser)
- Volkswagen
Fault code P0048 can sometimes be found with other errors. The most common are the following: P0045, P0046, P0047, P0049, P0100, P0400, P0440, P0441, P0404, P0446, P004A, P004E, P3348.
