Fault code P012B – turbocharger/supercharger inlet pressure sensor circuit range/performance (downstream of throttle valve)

Fault code P012B is called “Turbocharger/Supercharger Inlet Pressure (TCIP) Sensor Circuit Range/Performance (Downstream of throttle valve)” 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 P012B

Stored fault code P012B indicates that the control module (PCM) has detected a problem in the turbocharger or supercharger system. In this case, a performance range mismatch has been detected in the turbocharger inlet pressure sensor circuit. Which is located after the throttle valve.

Fault code P012B – turbocharger/supercharger inlet pressure sensor circuit range/performance (downstream of throttle valve)

In systems with forced induction, the inlet pressure must be varied and adjusted according to the power required at the time. This is done by using a boost regulating valve. This is monitored and controlled by the engine control module to provide the engine with the ideal fuel/air mixture.

This is accomplished by mechanically adjusting the turbocharger/charger blades. The blades are responsible for adjusting the amount of boost that delivers air into the combustion chamber. If the PCM loses control of the supercharger, it causes the engine to run erratically.

Fault code P012B is activated when the engine control module detects that a mismatch has occurred in the operating range of the turbocharger inlet pressure sensor circuit. This specifies which specific inlet sensor has the fault and its location. Namely, after the throttle valve.

After that, the controller turns on the check engine light (CEL). And the error is recorded in the memory as a malfunction in the supercharger control system.

It may take several failure cycles to turn on the MIL control lamp, on the dashboard.

Symptoms of vehicle malfunctions

The main signal that an error P012B has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check Engine” control lamp on the control panel will light up (the code will be recorded in the memory as a fault).
  2. Floating revolutions, as well as attempts to stall at idle.
  3. Jerking/missing ignition at idle or under load.
  4. Engine cannot be accelerated, throttle response is unresponsive.
  5. Reduced engine power output.
  6. Increased fuel consumption.
  7. Increased noise of the engine, also a ringing and rattling may be present.
  8. The vehicle may go into emergency operation mode.

The severity level of fault code P012B can be medium to high, depending on the symptoms. This error should not be ignored, as you risk damaging internal engine components. Therefore, it is in your best interest to troubleshoot the forced induction system as soon as possible.

Factors that can cause this error code

The error code P012B can mean that one or more of the following problems have occurred:

  • Faulty turbocharger inlet pressure sensor.
  • Corrosion causing high resistance in connectors or contacts.
  • Worn or shorted wiring.
  • Clogged or damaged air filter.
  • Exhaust gas leakage.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P012B

Some suggested steps for troubleshooting and fix the error code P012B:

  1. Read all stored data and error codes with an OBD-II scan tool.
  2. Clear the error codes from the computer memory and test-drive the vehicle to see if error P012B appears again.
  3. Check the turbocharger inlet pressure sensor.
  4. Inspect the air filter, it may need to be replaced.
  5. Test the connector and wiring for damage, looseness, and corrosion.
  6. Check PCM module.

Diagnose and repair of problems

Turbines typically spin at incredible speeds of 100,000 to 150,000 rpm. They are intolerant to imbalance or a lack of clean oil in the bearing.

The diagnostic process for the P012B error is best started with the most common turbo problems. These will require tools such as a vacuum gauge and a dial gauge.

Checking the vacuum

Make sure the engine is running properly, with no ignition skips or codes related to a faulty detonation sensor. Then, check for leaks at the turbocharger outlet, intercooler, and throttle body.

Inspect the intake manifold for leaks of any kind, including vacuum hoses. Remove the lever from the throttle valve. Manually operate the valve, looking for a jammed valve causing a drop in boost.

Measuring boost pressure, turbocharger inspection

Locate the vacuum with no holes in the intake manifold and install a vacuum gauge. Start the engine. At idle the engine should have a vacuum of 1-1.5 atmospheres. If less than 1 atmosphere then the catalytic converter is defective and will not allow boost.

Quickly accelerate the engine to 5000 rpm and release the throttle, observing the vacuum gauge showing the boost pressure. If the boost pressure rises above 1.3 atmospheres, then the bypass valve is bad.

Stop the engine and let it cool down. Remove the turbine exhaust hose and look inside to make sure the blades are not rubbing the housing. Look for bent or missing blades or oil in the turbocharger. Rotate the blades by hand, looking for resistance indicating turbocharger malfunction.

Inspect the oil lines from the cylinder block to the center bearing and the return line from the bearing to the oil pan for leaks. Place a dial gauge on the turbine outlet and rotate the turbine shaft. If the axial play exceeds 0.003, the center bearing is defective.

Wiring and pressure sensor

If after all the checks there is no problem, but code P012B has not disappeared, check the electrical components. The sensor and associated circuits should be tested.

Disconnect the wiring harness and test the control circuit. Make sure that 12 volts are present in the power circuit. They should show when the ignition is on. If they are not, or if they are present when the ignition is off, repair the wiring from the PCM to the sensor.

Check that the grounding is secure. Connect the test lamp to the plus side of the battery, and touch the other end to the sensor ground circuit. If the test light does not come on, this indicates a faulty circuit.

On which vehicles does this problem occur most frequently

Fault code P012B can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Dodge
  • Ford (F-150)
  • Honda
  • Mercedes-Benz (Sprinter)
  • Nissan (Frontier, NP300, Navara, Pathfinder, Qashqai)
  • Renault
  • Saturn
  • Subaru
  • Volkswagen (Crafter, Jetta, Tiguan)

Fault code P012B can sometimes be found with other errors. The most common are the following: P0113, P012A, P012C, P012D, P012E.


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