Richard McCuistian, ASE Certified Master vehicle Technician

Technical Reviewer at

Written through Staff writers - updated on respectable 12th, 2021

When the ECM/PCM detects a trouble with the signal sent out by the Manifold Absolute pressure (MAP) sensor the P0108 code will be save by the ECM/PCM. Learn more about this code in the following guide.

You are watching: P0108 manifold absolute pressure/barometric pressure circuit high input

What go the P0108 password Mean?

Diagnostic trouble code (DTC) P0108 code stands for “Manifold absolute Pressure/Barometric press High.” that is prompted by the ECM as soon as it receives a signal native the MAP/BARO sensor circuit that is over the typical range.

Typically, the MAP/BARO sensor is provided with regulation volts through the ECM ~ above a 5-volt recommendation circuit. Larger Fords usage a three-wire sensor that uses 5 volts, but the calculation signal no a voltage, that a frequency. At sea level through the engine off and also the vital on, a Ford MAP sensor commonly reads about 158 hertz, yet when the engine starts, the frequency fall to around 110 hertz. Top top this type of MAP sensor (as well together on the analog voltage form sensors provided by GM, Dodge, and some various other makes), an in-range failure of the MAP sensor can reason issues there is no a MAP sensor code being set.

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

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

Poor engine performance

A failure in the MAP/BARO sensor circuit might also affect the drivability of your vehicle. Your automobile may come to be hard come start, hesitate during acceleration, stall unpredictably, or experience rough idling.

How to Diagnose the P0108 Code

Now the we recognize what causes a P0108 code as well as its symptoms, the next step is identify which issue has motivated this password to it is in logged on her vehicle. Nothing hesitate to take your auto to a expert if you unsure of performing the diagnosis.If you’re an proficient DIY-er trying to find advice ~ above testing and fixing this trouble password yourself, below are part videos that may provide you a better idea that what the troubleshooting process might involve:

How to fix the P0108 Code

The P0108 code is a share DTC, which means it’s supported by various makes and models. While most vehicles will experience similar symptoms, the steps for diagnosis and repair might be different between car models.

If she unsure about having sufficient technical understanding to settle the password yourself, it’s finest to bring your car to the nearest auto fix shop for expert advice. If you decision on doing that on her own, fix manuals (like those from Chilton) and an ALLDATA auto subscription are an excellent resources for factory repair information.

Intake Manifold Pressure

There room a pair of simple types that fuel injection systems (pre-GDI). One of these is a “speed density” system, whereby there is a pressure sensor reading Intake manifold pressure (a.k.a., “manifold pure pressure”) to recognize engine load. The other kind (not discussed in this article) is the Mass air flow (MAF) form system. Part MAF systems additionally have a MAP sensor.

We speak a lot around intake manifold vacuum, yet MAP is usually a measure up of the differential in between ambient atmospheric pressure and also the pressure in the manifold.

Ambient atmospheric push at sea level measure in PSI is 14.7. In the metric system, that’s 1 BAR.

That’s what we call atmospheric pressure, and also it decreases v altitude. Yet the ECM/PCM procedures barometric pressure and also intake pressure in customs of mercury (that’s just how it’s measured, using a i graduated tube and a collection amount that mercury). Each PSI of pressure equals about 2 customs of mercury (Mercury is “Hg” ~ above the routine table).


If, for example, barometric pressure is 30 inches of mercury and engine vacuum is 20 inches of mercury idling, then manifold absolute pressure is, at the point, 10 inch – i m sorry is the difference in between 30 inches and also the 20 inch of manifold vacuum. Manifold vacuum is produced by the pistons developing low pressure as they take trip down on their intake strokes v the throttle plate closed and airflow in ~ a minimum.

As the throttle plate opens and the engine is loaded, manifold push increases and vacuum decreases. Thus, manifold push is specific indicator of engine load. That’s why part older automatic transmissions had a vacuum line from the manifold associated to the transmission modulator valve to modify transmission shifts under load.

So, manifold absolute pressure is offered by the ECM/PCM to calculate engine load, i m sorry is the primary input the ECM/PCM supplies to determine fuel injector pulse width while the engine is doing its work. The greater the measure up MAP, the more comprehensive the fuel pulse through each injector event.

When the crucial is switched top top initially, the ECM/PCM documents closed throttle voltage, intake air and also engine coolant temperature, and also barometric press using the MAP sensor. These determinants determine how much fuel is yielded when the engine is starting and after the fires up.

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Products mentioned in this Guide

Catalytic Converter
Barometric pressure Sensor
MAP Sensor

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