Boost Pressure Sensor

If you have a turbocharged engine, you know how important the boost pressure sensor is. You also know when the boost pressure sensor is malfunctioning, you’re going to have problems. When the boost pressure sensor fails, the information is sent to your car’s computer in the form of the P0236 OBD2 diagnostic trouble code (DTC). If you’re not sure what the boost pressure sensor is and why it is so important to turbocharged engines, read on to find out what it is, what it does, and what to do when it goes bad.

Boost Pressure Sensor

The boost pressure sensor is a part of the turbocharged system and is located inside the intake pipe that lies close to the throttle valve. The turbo engine is made up of the compressor and the turbine which spin at high speeds to generate more air. The sensor serves many roles. For one, the sensor measures the absolute air pressure in the intake manifold.

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The sensor also regulates the air flows and measures the speed. Second, the boost pressure sensor controls boost levels in the turbocharged engine. The sensor affect the amount of air pressure that is delivered to the pneumatic and mechanical wastegate actuator. The boost pressure sensor is also used to measure the intake air mass. Overall, the sensor maintains the equilibrium of air/fuel mixtures which go into the engine.

You may be wondering is there a difference between the regular engine and the turbocharged engine? Yes, even regular internal combustion engines have the same air/fuel mixture. When the gas burns, the energy it generates is used to power the engine. The supply of air is not the same in the regular internal combustion engine. The turbo engine sucks in much more air in order to produce more power.

Boost Pressure Sensor P0236 Trouble Code

The P0236 “Turbocharger Boost Sensor A Circuit Range/Performance” OBD2 code means the ECM has detected irregular intake boost pressure sensor A input circuit range when compared to the manifold pressure sensor and the barometric pressure sensor when the car is turned off.

This code applies to all types of turbocharged engines. Although the OBD2 codes do not name a particular part as the problem, they do point to the area that is having the problem.

Causes of P0236 Code

Turbotechnology has become extremely popular among racing enthusiasts and also in other recreational disciplines. Keeping the turbocharged equipment maintained can be a challenge.

Since the internal combustion engine runs on a mixture of fuel and air, when the mixture or inflow process is disrupted, it causes engine problems.

There may be one or a few causes for a P0236 trouble code in turbocharged vehicles. Here are the most common reasons:

1. Different sensor readings – The turbo boost pressure sensor and the manifold absolute pressure (MAP) sensor and barometric pressure (BARO) sensors do not have the same readings. The MAP measures the engine load mostly by monitoring how much air flows into the engine so that the Powertrain Control Module (PCM) can measure the air density, regulate the amount fuel spray that enters into the combustion chamber, and also manage the ignition timing.

Because there is an inverse relationship between the pressure and vacuum, the PCM can measure the engine vacuum and load from the MAP signal in addition to the other readings. The barometric pressure (BARO) sensor measures atmospheric pressure.

Typically, the barometric pressure is about 28 – 31 inches of mercury (Hg) while the engine vacuum measure is about 17 – 22 inches (Hg) at sea level. When you start your car, the PCU retrieves the barometric pressure measurement from the MAP sensor.

2. Contaminated or clogged boost pressure sensor – Engines collect all sorts of deposits over time. The boost pressure sensor should be cleaned periodically to avoid becoming clogged or contaminated. When the sensor is removed, you can see all of the crud covering its protruding parts. Boost pressure is regulated by the ECU. When the ECU can no longer control the boost pressure, the fueling is reduced. Limp mode is the reaction when the computer in your car detects a problem that could seriously harm your engine or transmission. The power is reduced to relieve the load on those parts.

3. Misfiring – Your spark plugs ignite the fuel and air mixture that enters the combustion chamber. When the sensor is not sending accurate information, the air/fuel mixture is no longer being lit in the regular pattern. This causes your engine to sputter and misfire. When you drive at higher speeds, you will notice the engine hesitate and eventually resume. That means the engine is getting some fuel, but amount of fuel is not sufficient.

You Treat Your Car Like Badly – Most vehicle owners understand that a vehicle must be inspected and serviced from time to time, as referred to as routine maintenance. For those who don’t, the likelihood of problems that cause the boost pressure sensor is extremely high. If the vehicle is not inspected routinely, small problems can escalate to major problems that are much more expensive to fix. This is also true for vehicles which sit for long periods of time.

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A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.

Symptoms of P0236 Code Problem

There are so many sensors involved in getting your car up and running, especially in the more modern vehicles with computer systems. However, these sensors can also cause major problems when they are dirty or damaged. Information exchanges break down. Here are the most common symptoms that you have a problem with the boost pressure sensor and that the P0236 code has been thrown:

Warning light – When sensors malfunction, it means that no signal can be read. The PCU reacts to the problem by reporting trouble codes. Depending on the year your vehicle was made, you may get different sensor and circuit faults. When the boost pressure sensor is malfunctioning or not working at all, the PCU will activate the Check Engine Light (CEL).

The appropriate trouble codes will be thrown the OBD2 system pertaining to the that area. In this case, the P0236 will be thrown and possibly trouble code P0235. You may also see an activated malfunction indicator lamp (MIL)  along with OBD2 diagnostic trouble codes (DTCs). This is one of the first signs that you have problems with the boost pressure sensor.

Intake Boost Sensor A slow – When the Intake Boost Sensor A is failing, it responds too slowly, it hampers the engine performance. There may be additional problems with the MAF. If the problem goes unchecked, your vehicle will eventually not run at all.

Loss of power – When the P0236 code is thrown, the PCM turns the turbocharger off. The vehicle loses power which reduces the performance. You know that a loss of power in your engine is definitely a sign that your vehicle needs an inspection.

Higher fuel consumptionMiscalculations on how much fuel and air is needed in the internal combustion engine can commonly cause higher fuel consumption. In turn, the higher fuel consumption causes higher EGTs. The higher EGTs mean your turbo system is not receiving sufficient air. The average fuel economy will show higher fuel consumption. You may even see black smoke coming from your exhaust.

Lack of acceleration – Poor acceleration and turbo lag are very common symptoms of a boost pressure sensor problem. The boost sensor is not registering the correct amount of boost pressure. If your car seems to struggle to accelerate, a bad boost pressure sensor be the cause. In some cases, the car may along very slowly as if it isn’t moving at all. The lack of acceleration indicates that something is going wrong under your hood and therefore it is time for an inspection.

Test the Boost Pressure Sensor

Testing the boost pressure sensor includes testing the supply voltage, the output signal and the temperature sensor. You will need a vacuum hand pump and manometer for the vacuum; a multimeter (view on Amazon); heating equipment; and a thermometer up to 100°C. Once you have gathered all of the materials, here are the steps to perform each test:

Test the supply voltage

1. Disconnect the plug from the boost pressure sensor

2. Turn on the ignition to your car

3. Set your multimeter measure range to the DC voltage setting.

4. Take a measure of the supply voltage between the earth (A) and the pin (C). The set point value is 5V. If the set point value does not reach 5V, the voltage supply must be searched for the fault.

Test the output signal

1. Take the pressure sensor out of the intake manifold

2. Connect the boost pressure sensor and the vacuum hand pump

3. Turn on the ignition in your car.

4. Set your multimeter measure range to the DC voltage setting.

5. Set the lower absolute pressure value plow

6. Test the lower output signal Ulow between earth (A) and pin (B). Set point value

7. Set the upper absolute pressure value Phigh

8. Test upper output signal Uhigh between earth (A) and pin (B)

9. Set point value. Note” Engine control unit earth faults can cause measured values from the intake manifold pressures sensor to be false, which will give an error message.

Test the temperature sensor

1. Take the pressure sensor out of the intake manifold

2. Turn on the ignition in your car.

3. Set your multimeter measure range to “Resistance”.

Using a hot air gun and thermometer to set one of these testing points: 25°C, 85°C or 100°C.

4. Measure resistance value between earth (A) and pin (B). If the measured value is not achieved, the intake manifold pressure sensor has to be replaced.

Check Your Logs

For those who own Stock Turbo, you should examine the WGDC Actual number. A WGDC reading which is higher than usual means there is trouble and could even mean a boost leak. Check to see if the WGDC number is 100% of the pull. Then check to see if the normal boost pressures are lower than usual. If both of these are the case, you may have to have some adjustments done to get the readings back to normal.

Related OBD2 Codes

In addition to the P0236 and the P0235, you may get trouble codes associated with MAP and BARO. For example, you may get the P0068 or the P0069:

Error Code P0068 “Manifold Absolute Pressure (MAP) Sensor/MAF Sensor/Throttle Position Correlation” – This code means that the PCM has identified inconsistency in the positioning of the Mass Airflow Sensor (MAF) and the throttle sensor. An excessive input voltage signal degree variation has been detected from the Throttle Position Sensor (TPS) compared to MAP and MAF input signals.

Error Code P0069 “Manifold Absolute Pressure (MAP) sensor/barometric pressure (BARO) sensor correlation”– Indicates a problem with the Map Sensor. The BARO sensor measures the atmospheric pressure.. When the car starts up, the PCU get the barometric measure from the MAP The most common causes are a problem with the MAP sensor, the BARO sensor, large vacuum leak, or faulty PCM.

Be Safe

Now you know all there is to know about the P0236 trouble code and what to do about it. If your car has a boost pressure sensor problem, have a repaired right away and drive safe.