Richard McCuistian, ASE Certified Master auto Technician

Technical Reviewer at moment-g.com

Written through moment-g.com Staff writers - to update on respectable 12th, 2021

When the ECM/PCM detects a difficulty with the signal sent out by the Manifold Absolute press (MAP) sensor the P0108 code will certainly be save on computer by the ECM/PCM. Learn more about this password in the adhering to guide.

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What does the P0108 password Mean?

Diagnostic trouble code (DTC) P0108 code represents “Manifold absolute Pressure/Barometric pressure High.” the is motivated by the ECM as soon as it receives a signal native the MAP/BARO sensor circuit the is above the regular range.

Typically, the MAP/BARO sensor is gave with regulated volts through the ECM top top a 5-volt reference circuit. Larger Fords usage a three-wire sensor that uses 5 volts, yet the calculation signal isn’t a voltage, that a frequency. At sea level with the engine off and the an essential on, a Ford MAP sensor typically reads about 158 hertz, yet when the engine starts, the frequency fall to about 110 hertz. On this type of MAP sensor (as well together on the analog voltage form sensors offered by GM, Dodge, and also some various other makes), one in-range failure of the MAP sensor can reason issues without a MAP sensor password being set.

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An problem with the MAP sensor deserve to throw off her car’s air/fuel ratio.

An worry with the MAP sensor have the right to throw off her car’s air/fuel ratio, leading to boosted fuel consumption.

Poor engine performance

A breakdown in the MAP/BARO sensor circuit might also affect the drivability of her vehicle. Your auto may end up being hard to start, hesitate during acceleration, stall unpredictably, or experience rough idling.

How to Diagnose the P0108 Code

Now that we know what reasons a P0108 code as well as its symptoms, the following step is identify which worry has motivated this code to it is in logged on your vehicle. Nothing hesitate to take your car to a experienced if you unsure the performing the diagnosis.If you’re an proficient DIY-er in search of advice top top testing and fixing this trouble code yourself, here are part videos that may offer you a much better idea the what the troubleshooting procedure might involve:


How to solve the P0108 Code

The P0108 password is a share DTC, which method it’s sustained by miscellaneous makes and also models. While most vehicles will certainly experience comparable symptoms, the procedures for diagnosis and repair may be different between car models.

If you’re unsure about having enough technical understanding to fix the password yourself, it’s best to bring your auto to the nearest auto repair shop for experienced advice. If you decision on doing that on your own, repair manuals (like those indigenous Chilton) and an ALLDATA auto subscription are great resources for factory repair information.

Intake Manifold Pressure

There space a couple of simple types the fuel injection equipment (pre-GDI). One of these is a “speed density” system, where there is a press sensor analysis Intake manifold press (a.k.a., “manifold pure pressure”) to recognize engine load. The other form (not debated in this article) is the Mass air flow (MAF) type system. Some MAF systems likewise have a MAP sensor.

We talk a lot around intake manifold vacuum, but MAP is basically a measure up of the differential in between ambient atmospheric pressure and the press in the manifold.

Ambient atmospheric press at sea level measure up in PSI is 14.7. In the metric system, it is 1 BAR.

That’s what we call atmospheric pressure, and it decreases v altitude. However the ECM/PCM steps barometric pressure and also intake push in inches of mercury (that’s just how it’s measured, utilizing a i graduated tube and a collection amount of mercury). Every PSI of pressure equals approximately 2 inches of mercury (Mercury is “Hg” on the routine table).


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If, because that example, barometric pressure is 30 inch of mercury and engine vacuum is 20 inches of mercury idling, then manifold absolute push is, at the point, 10 inches – i m sorry is the difference between 30 inches and the 20 inches of manifold vacuum. Manifold vacuum is produced by the pistons developing low press as they travel down on your intake strokes v the accelerator plate closed and airflow in ~ a minimum.

As the accelerator plate opens and the engine is loaded, manifold press increases and also vacuum decreases. Thus, manifold push is precise indicator of engine load. It is why part older automatically transmissions had actually a vacuum heat from the manifold connected to the transmission modulator valve to modify transmission shifts under load.

So, manifold absolute push is offered by the ECM/PCM to calculate engine load, i beg your pardon is the main input the ECM/PCM supplies to determine fuel injector pulse width while the engine is act its work. The greater the measured MAP, the broader the fuel pulse v each injector event.

When the key is switched on initially, the ECM/PCM documents closed accelerator voltage, input air and engine coolant temperature, and barometric pressure using the MAP sensor. These factors determine just how much fuel is yielded when the engine is starting and after the fires up.

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Products stated in this Guide


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Catalytic Converter
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Barometric push Sensor
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MAP Sensor

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