Error Code P0105: Manifold Air Pressure (MAP) Barometric Pressure Sensor Electrical Circuit Problem

Error Code P0105 is defined as MAP (Manifold Absolute Pressure) sensor BARO (Barometric Pressure) Sensor Malfunction. This refers to MAP circuit malfunctioning or having electrical failure. The MAP sensor plays a big role in fuel injection system as it provides signals for the ECU (Engine Control Unit) for good fuel economy and smooth operation.

Definition

The MAP sensor is a component of fuel management system. It works by reacting to changes in the engine manifold pressure. The PCM (Powertrain Control Module) continuously checks this sensor to ensure the engine is running properly. Any changes in the engine load will require changes in the ignition system timing, level of fuel injected, etc.

An engine under load has more manifold pressure (or less vacuum) than a coasting engine. When the load change, the MAP sensor acts by sending a voltage signal to the PCM for it to change accordingly. To check and verify the signal of the MAP sensor and ensure it runs properly, the PCM will monitor other sensors.

For example, the PCM will compare TPS (Throttle Position Sensor) signal to the MAP signal to verify if the signal is not “sticking”. If the PCM determines the MAP sensor doesn’t change immediately following a change in the TPS, then it has determine a problem with the MAP sensor, setting the error code P0105.

If the PCM reads that TPS indicates the engine is under load, but MAP signal says it’s coasting, then again, it sees a malfunction in the MAP sensor or TPS, and will set the same error code.

Common Symptoms

The most common tell-tale sign of this error code is of course, the illumination of Check Engine light. Some of the most common symptoms associated with this code are:

  • Hard starting
  • Reduced engine power
  • Hesitation upon acceleration
  • Increase in fuel consumption
  • Engine backfire through tailpipe
  • Engine running rich
  • Engine won’t idle

These symptoms vary from severity and from one vehicle to another.

Possible Causes

The most common causes for this code is in wiring issues, MAP sensor, or BARO sensor problems, sometimes in the ECM itself. Many times, the source of the problem is caused by sensor range voltage output being out of ECU’s programmed input. Other possible causes include:

  • Cracked, damaged or kinked vacuum hose
  • Damaged wiring
  • Broken MAP
  • Broken TPS
  • Problematic or damaged MAP sensor or TPS sensor connector
  • Disconnected MAP sensor vacuum
  • Short to reference voltage on MAP sensor’s signal circuit
  • MAP sensor has open on signal circuit
  • Loss of ground to TPS of MAP
  • Damaged PCM (rare)

How to Check

The diagnosis for P0105 starts with clearing and rechecking the code and see if it comes back during a test drive. A qualified mechanic will observe it through their special scanner’s live stream data. If the Check Engine warning comes back and the error code is once again set, then a thorough visual inspection is needed.

The mechanic will inspect the vacuum line and other hoses on the intake system and see if there’s a loose, disconnected, damaged, or missing hose. If everything seems fine, the technician will proceed to conduct a voltage output test of the sensor while the engine is on to determine whether the voltage output fluctuates with engine load and speed.

How to Fix

  1. To fix this error code, again, it starts with verifying the code through the scanner and resetting the fault code before conducting a road test. This usually solves the issue in some cases.
  2. If the code comes back, you will need to check the vacuum lines, wirings and electrical connectors. Refresh the connections by disconnecting the electrical connector and plugging them again.
  3. For the vacuum leaks, check the clamps and look for loose hoses on the intake. This is especially important for older vehicles.
  4. If everything seems good, and error code is still there, then your MAP sensor may be damaged and needs to be replaced.

If you’re not confident with your own diagnosis, then it would be better if you take your vehicle to your dealer or to a qualified mechanic for a thorough and professional diagnosis. It is important to insure there are no intake air leaks like damaged vacuum hose or in other air connections. Also, technicians will verify the voltage output of the MAP sensor to ensure it stays in correct range and fluctuates together with the engine speed. Never replace your MAP sensor unless you’re sure it’s the one causing the error code.

This code requires immediate attention, as continuous running with this problem will not only cause excessive fuel consumption and rough operation, but can also damage the engine further.

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