OBD2 Trouble Code P0108

OBD2 Trouble Code P0108

Your car’s computer relies on various sensors to make sure your car’s engine runs efficiently. When a sensor begins sending abnormal readings to the computer, it can cause the engine to run poorly.

What Does P0108 – “Manifold Absolute Pressure Barometric Pressure Circuit High” Mean?

To explain this diagnostic trouble code (DTC), we need to break it down into its individual parts.

  1. The MAP, manifold absolute pressure, is one of the measurements that the engine’s computer (PCM) uses to calculate the air to fuel ratio.
  2. The barometric pressure circuit is a group of wires and sensors that measure the amount of air going into the motor.
  3. High is short for “higher voltage than normal,” and it means that the PCM is receiving a signal from one of the sensors that is above operating range.

When you put it all together, there is an issue with the sensor’s readings. Specifically, it means that for some reason, more voltage is going to the car’s computer than there should be.

Sometimes the sensor will momentarily malfunction because of an electrical short, static discharge, or abnormal engine condition. If that happens, there may not be any symptoms beyond your check engine light being illuminated. Your OBD2 scanner will be your best diagnostic tool for this code.

How Serious Is Code P0108?

The MAF sensor is responsible for telling the computer how much air is going into the engine, so when it malfunctions you may experience rich or lean conditions as well. Lean conditions can cause damage to the vehicle, so it’s important to get the issue fixed quickly.

While it is unlikely that there will be immediate damage to the car, make sure to stop driving if you experience one of the following severe symptoms.

Stop Driving

  • The engine is running very roughly
  • You hear loud banging or knocking
  • The check engine light begins flashing

Related Sensors

  • Mass airflow (MAF)
  • Manifold absolute pressure (MAP)
  • Throttle position switch (TPS)
  • Camshaft position – rare

Symptoms

The following symptoms are the most common symptoms. We don’t discuss other symptoms because some vehicles use different programs that use the sensors differently. Your scan tool will be the most effective diagnostic tool.

  • Check engine light is illuminated
  • Engine hesitates or surges sometimes
  • The fuel economy gets worse
  • The ar occasionally backfires after starting

Causes

There are a handful of problems that can cause a high-voltage scenario.

  • MAP sensor failure
  • Vacuum leak
  • Wiring issue
  • The engine has another issue

Solutions

The solution to the issue is going to depend on which part has failed. You’ll want to take the following steps to find and fix the problem.

Locate and Inspect the MAP Sensor

You’ll want to locate the MAP sensor and inspect the vacuum lines and electrical wires going to it. Corrosion can damage electrical connections and cause a short. An open circuit because of a broken wire will cause this error. If you find cracked or broken lines or wires, replace them, and you may solve the issue.

Replace the MAP Sensor

If everything seems ok after a visual inspection, the most likely problem is that the MAP sensor itself has failed. Replacing the MAP sensor is fairly straightforward,  and they are usually inexpensive. You may need to drive around a bit before the computer will re-learn and clear the code.

Do a Vacuum Leak Test

The next step if the problem isn’t solved is to do a smoke test. A smoke test will test for vacuum leaks, and you can learn about how to perform that here. If the car is leaking air or sucking in extra air, it may cause very abnormal sensor readings.

Do a Leak Down Test

A leak down test is a type of compression test, and it is a good test to determine the viability of a motor. Mobile Oil has a good write-up on the process. Unfortunately, it can be a very expensive and time-consuming issue to fix if you have compression issues. Don’t be afraid to take the car to a mechanic and get a second opinion.

While this code can cause problems, more often than not it’s likely a voltage issue. Unfortunately, if you learn that this isn’t the case, it’s important to consult with your mechanic as soon as possible.