P0105 – Manifold absolute pressure (MAP) sensor barometric pressure (BARO) sensor -circuit malfunction

Reinier

By Reinier (Contact Me)
Last Updated 2016-06-02
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P0105 Manifold absolute pressure (MAP) sensor barometric pressure (BARO) sensor -circuit malfunction Wiring, MAP sensor, BARO sensor, ECM

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What Does Code P0105 Mean?

OBD II fault code P0105 is defined as “Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction”, and is set when the Powertrain Control Module detects a signal voltage from the MAP (Manifold Absolute Pressure) sensor that is either abnormal with regard to the current engine load and/or throttle position, or a signal from the MAP sensor that does not correlate with the signal voltage from the TPS (Throttle Position Sensor).

As engine loads/speeds change, the pressure (or vacuum) in the intake manifold also changes in response to the varying demand. As a result, the MAP sensor generates signal voltages based on the pressure changes, which the PCM (Powertrain Control Module) uses to calculate appropriate fuel delivery strategies and adaptations to the ignition timing to keep the engine performing at peak efficiency.

To monitor the accuracy of MAP sensor readings the PCM uses other sensors, most notably the TPS (Throttle Position Sensor) to verify the correct operation of the MAP sensor. Thus, should the PCM detect a “mismatch” between the signals from the MAP and TPS sensors, the PCM will recognize a fault condition, and code P0105 will be set.

In practice though, the TPS sensor “leads” the MAP sensor, in the sense that the PCM expects to detect a change in the signal voltage from the MAP sensor immediately the throttle position changes, which change produces a signal voltage against which the subsequent correct functioning (or otherwise) of the MAP sensor can be gauged.

However, this scenario assumes that both the MAP and TPS sensors and associated circuits are functioning properly, but it is possible for a defective TPS sensor to also cause code P0105 to be set when its signal voltage does not match that of the MAP/BARO sensor.

The images below show typical MAP/MAF/TPS sensors, but note that these images are for informational purposes only. However, although the designs of these sensors differ from vehicle to vehicle, any or all three sensors shown here could be implicated in OBD II fault codes that are closely related to P0105- i.e., P0106, P0107, P0108, and P0109.

Typical MAP sensor

mapsensor

MAP sensors are always located directly on the intake manifold, where they monitor changes in manifold pressure.

Typical MAF sensor

mafsensor

MAF sensors are always located directly in the inlet tract, although their actual position in the tract can differ from vehicle to vehicle. Note the elements that generate a signal voltage when inlet air passes over them. Other applications could have more, or fewer elements.

Typical TPS (Throttle Position) sensor

tpssensor

Throttle position sensors are located on the throttle body, which should not be confused with the MAF sensor that is located elsewhere in the inlet tract. In this application, the actual TPS is the black plastic unit secured to the aluminum throttle body with two screws. Note the connector with three wires leading out of it.

Note: “Circuit Malfunction” indicates that there is a malfunction in the control circuit, as opposed to a fault in a sensor or other component. With “Circuit Malfunction” codes, replacement of sensors and components in the affected circuit will almost never resolve the problem, since as the code suggests, the trouble is in the circuit. This distinction between “circuit” and “sensor/component” is a great help to anyone trying to diagnose a circuit malfunction code, since it narrows the list of possible causes down considerably.

What are the common causes of code P0105 ?

Common causes of code P0105 are much the same for all applications; however, the symptoms of code P0105 may not present in the same way on all applications. For instance, vacuum leaks (which can set code P0105) on some, if not most, BMW models can cause uncontrollable surging followed by severe stumbling. Other applications may not be affected in the same way, or to the same degree, but this code could be set as a result of vacuum system issues on many applications nevertheless. Common causes of code P0105 include the following-

  • Misfire, or lean-running conditions may be present.

  • Unmetered air entering the inlet tract through leaking gaskets, or ruptured/dislodged/degraded vacuum hoses/lines or inlet ducting.

  • Open/short circuits in associated wiring due to corrosion or physical damage to wiring.

  • Defective MAP/MAF/BARO/TPS sensors.

  • Clogged catalytic converter(s).

  • Loss of ground contact to MAP sensor.

  • Loss of ground contact to TPS sensor.

  • PCM failure, although this is rare.

What are the symptoms of code P0105 ?

Although the most common symptoms of code P0105 are much the same on all application, the severity of one or more symptoms may vary from vehicle to vehicle. Below are some of the most common symptoms associated with code P0105-

  • Illuminated check engine light, and a stored fault code.

  • Possible increased fuel consumption.

  • Possible hard starting.

  • Reduced engine power.

  • Hesitation upon acceleration.

How do you troubleshoot code P0105 ?

NOTE #1: On most applications, the primary code setting parameter is when an incorrect/mismatched/poorly correlating signal is detected for a continuous period of 4 seconds or more. The value of the actual signal is compared to a reference voltage, which may be different for some vehicles, although reference voltages from the MAP sensor typically vary between about 1 volt (or slightly less) for engines running at idle, and 4.5- to 5 volts for engines running at wide throttle openings.

Typical reference voltages (about 1 volt to 4.5 volts) from the TPS should closely match those obtained from the MAP sensor as the engine speed and load changes. Consult the repair manual for the vehicle being worked on for exact signal values.

NOTE #2: Accumulated dirt and oily residues on the MAF (Mass Airflow) sensor element can lead to incorrect signal voltages being generated. Therefore, on vehicles that are equipped with MAF sensors, cleaning the element with an approved cleaner as a first step in the diagnostic/repair procedure will often resolve code P0105, as will cleaning/repairing/replacing corroded electrical connectors on all relevant sensors, i.e., the MAP, MAF, and/or combined MAF/BARO sensors.

NOTE #3: Diagnosing code P0105 requires that the engine be in perfect running condition. If misfire, or vacuum system related codes are present along with P0105, resolve these codes first before attempting to diagnose and repair code P0105.

Step 1

Assuming that there is no visible damage to sensors, wiring, and connectors, begin the diagnostic procedure by checking freeze frame data with a suitable scanner or code reader. Note that the ignition should be “ON”, with the engine “OFF” for this step. If freeze frame data is available, it will serve as a sort of snapshot of the code setting parameter identifiers, which serves to more accurately identify the root cause of code P0105.

NOTE: In a “key-on-engine-off” condition, the MAP sensor signal should read about 4 volts if you are at sea level, on account of the high ambient atmospheric pressure. As a rule of thumb, this reading should decrease by about 0.5 volt for each 1 000ft of elevation above sea level, although this value could be different for some applications.

TIP: On vehicles that are fitted with combined MAF/BARO sensors instead of MAP sensors, the BARO and MAF voltages should match. If no issues are discovered with damaged or corroded connectors and the code persists after cleaning the MAF sensor element, perform a thorough inspection of all associated wiring. Repair/replace damaged wiring as required to eliminate open circuits, short circuits, and continuity/ground/reference voltage issues.

Step 2

At this point, also check for a clogged/dirty air filter element, clogged or damaged catalytic converter(s),damaged or disconnected air inlet ducting, dislodged or ruptured vacuum lines, and obstructions in the inlet tract. Repair/replace hoses, ducting, the filter element, or vacuum lines as required. Clear the code, and test the vehicle to see if the code returns.

Step 3

If the code persists, check for the specified reference voltage at the MAP sensor connector. Also check for ground and continuity, especially in the signal wire between the PCM and the MAP sensor connector, but be sure to disconnect all control modules before commencing continuity checks. If the signal wire shows infinite resistance, repair the open circuit in the MAP signal circuit.

Consult the repair manual to determine the color-coding and location of the wires in the connector. Repair power supply, continuity and ground issues as required. Clear the code, test the vehicle, and rescan the system to see if the code returns.

NOTE: One wire in the connector carries the voltage signal to the PCM, while the other wires supply the reference voltage and ground.

Step 4

If all reference voltages and ground readings fall within specifications, and continuity is OK, test the MAP sensor by applying a vacuum to it. Use a scan tool to monitor the result of the vacuum test, but be sure to refer to the manufacturers pressure to Hertz chart to interpret the obtained reading correctly.

The voltage from the MAP sensor should progressively decrease from about 5 volts to about 1 volt or slightly less as a progressively stronger vacuum is applied to the sensor, and increase back up to about 5 volts as the vacuum is released. If the signal voltage does not change according to the manufacturer’s specification, replace the MAP sensor if its seal is found not to be hardened, split, or cracked.

Also “wiggle” the MAP sensor connector around a bit while the sensor is under a vacuum, and check to see if the signal voltage fluctuates. If it does, the connector is causing bad contacts. Repair/replace the connector as required. Repeat the vacuum test after repairs to confirm that the connector issue had been resolved.

NOTE: In some applications, the signal from the MAP sensor could appear to be “stuck” at about 0.5 volt, but there is no way of knowing for sure on which vehicles and applications such a low voltage signal will set code P0105.

What is more likely to happen is for the MAP sensor voltage to be “stuck” at around 4.5 volts, regardless of the amount of vacuum applied. If this happens, remove the sensor signal wire from the PCM connector, and check the voltage on the wire. If about 4.5 volts is found, unplug the connector from the MAP sensor, and check the voltage in the signal wire again. Should there still be a 4.5 volt current present, there is a short circuit between the signal wire and the 5-volt reference wire. Repair/replace wiring as required to eliminate the short circuit.

If however, the current on the signal wire disappears after unplugging the MAP sensor connector, and there is a good ground, there is an internal short circuit in the MAP sensor, and it must be replaced.

Step 5

Once all repairs/replacements are complete, clear the code and test-drive the vehicle to see if the code returns. If the code (and symptoms) persists despite repeated checks and repair attempts, there might be an intermittent fault that could require you to allow it to worsen before an accurate diagnosis and repair could be made.

In some cases, the PCM might be defective, or in the process of failing, but this is exceedingly rare, and the fault must be sought elsewhere before the PCM is replaced.

Codes Related to P0105

  • P0106 – Relates to Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

  • P0107 – Relates to Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

  • P0108 – Relates to Manifold Absolute Pressure/Barometric Pressure Circuit High Input

  • P0109 – Relates to Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

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