Fault code P2578 – turbocharger speed sensor circuit malfunction

Fault code P2578 is called “Turbocharger Speed Sensor Circuit Malfunction” 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 P2578

This diagnostic trouble code (DTC) is a generic transmission code. Error P2578 is considered a generic code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

Fault code P2578 – turbocharger speed sensor circuit malfunction

The turbocharger speed sensor converts the turbine speed into an electrical signal for the Powertrain Control Module (PCM). This information is typically used to fine-tune the amount of boost provided to the engine by the turbocharger.

In addition, the PCM also receives other information needed to calculate the boost pressure. And when there is a problem with the turbocharger speed, the PCM will detect the problem and set the code P2578. This error is relevant to the electrical circuit going to the sensor.

The troubleshooting steps may vary depending on the manufacturer, the type of sensor, and the colors of the wires going to the sensor.

Symptoms of vehicle malfunctions

The main signal that an error P2578 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Check engine control lamp on the control panel will light up (the code will be recorded in the ECM memory as a fault).
  2. Decrease of engine power.
  3. The engine does not accelerate well.
  4. Increased fuel consumption.
  5. Black smoke coming out of the exhaust pipe.
  6. Unusual noises from turbocharger or manifolds.
  7. Whistling noises may be coming from the hoses or bypass valve.
  8. Possible detonation in cylinders.

The severity of fault code P2578 is usually moderate, but can quickly escalate to a more serious level if not corrected in a timely manner.

Factors that can cause this error code

The error code P2578 can mean that one or more of the following problems have occurred:

  • Open circuit in turbocharger speed sensor signal circuit.
  • Voltage or ground fault in turbocharger speed sensor signal circuit.
  • Voltage or ground fault in turbocharger speed sensor signal circuit.
  • Faulty turbocharger pressure control actuator position sensor.
  • In very rare cases PCM transmission control module may be damaged.

How to fix or reset OBD-2 code P2578

Some suggested steps for troubleshooting and fix the error code P2578:

  1. Check sensor signal circuit, correct if necessary.
  2. Check for a ground fault.
  3. If a supply or ground fault is detected, correct the cause.
  4. If necessary, replace the faulty position sensor of the turbocharger pressure control actuator.
  5. If the PCM has failed, flash or replace it.

Diagnose and repair of problems

Locate the turbocharger speed sensor, it is usually screwed or bolted directly to the turbocharger housing. Visually inspect the connector and wiring. Look for scratches, scuffs, exposed wires, burn marks or melted plastic.

Disconnect the connector and carefully inspect the terminals inside the connector. Note the green tinge of oxidation or corrosion. If necessary, clean or replace the terminals or connector.

If you have a diagnostic tool, clear the diagnostic trouble codes from the memory and see if code P2578 returns. If it does not, you need to continue detecting the problem.

Next, test the turbocharger speed sensor and associated circuits. With the key turned off, disconnect the electrical connector on the turbocharger speed sensor. Connect the black wire of the digital voltmeter to the ground terminal on the sensor wiring harness connector.

Connect the red wire of the digital voltmeter to the power terminal on the turbocharger speed sensor harness connector. Turn the key to the engine on position. The voltmeter should read either 12 or 5 volts. If not, repair a break in the wiring in the power or ground wire, or replace the PCM.

If the previous test passes, we will need to check the signal wire. Without removing the connector, move the red voltmeter wire from the power wire terminal to the signal wire terminal. The voltmeter should now show 5 volts. If not, repair the break in the signal wire or replace the PCM.

If all previous tests are passed but error P2578 remains, it most likely indicates a failed turbocharger speed sensor. Although a failed PCM cannot be ruled out until the sensor is replaced.

On which vehicles does this problem occur most frequently

Fault code P2578 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 (A8, Q7)
  • Skoda
  • Volkswagen (Touareg)

Fault code P2578 can sometimes be found with other errors. The most common are the following: P2579, P2580, P2581, P2582.

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