If you've noticed that your vehicle suddenly needs diesel and that you are spending more money than you are used to at the pump, you may wonder what's going on. You may also notice that your check engine light has come on, and thus there is clearly something wrong within your management system. In this case, you may find that you have a faulty manifold absolute pressure (MAP) sensor, but as you've never heard of this gizmo before, what is it supposed to do and what could be going wrong?
Sensing an Issue
As you may know, your diesel vehicle is equipped with dozens of individual sensors that are designed to detect anomalies and warn the driver through a dashboard light. In this case, the manifold absolute pressure sensor may be defective and has sent an incorrect message to the powertrain control module (PCM). The PCM module has then made alterations to the fuel-to-air mixture and has triggered the warning.
Problems for You
As the mixture was probably okay before, you may notice that the vehicle is not as responsive as it was previously and that you are, indeed, using more diesel than you should. In this case, you will need to replace the sensor.
What the Sensor Should Do
When the sensor is working correctly, it is trying to determine the pressure level within the combustion chamber. It is programmed to register atmospheric pressure and to read the pressure when the engine is running. Ideally, this pressure should be close to zero PSI at this time, which would indicate a vacuum, and this is the ideal situation for engine operation. However, as the sensor thinks that the intake manifold pressure is high, the powertrain control module has increased the amount of fuel being injected into the chamber to try to compensate. This will not only increase your fuel usage, but it will also elevate the emission levels, and your vehicle will be likely to fail a carbon monoxide check.
Take your diesel vehicle into a mechanic so they can decipher the code provided by the powertrain control module. They'll narrow the problem down to your faulty sensor so that it can be changed, and you can get back to normal driving. Try not to delay any longer than you need to, as this issue could cause problems elsewhere if it is left unchecked. Call sources like Bosch-authorised diesel dealers to get more information about handling diesel vehicles.