P0103 – Mass air flow (MAF) sensor/volume air flow (VAF) sensor high input

By Ti (Contact Me)
Last Updated 2016-06-02
Mechanical Engineer

Trouble CodeFault LocationProbable Cause
P0103 Mass air flow (MAF) sensor/volume air flow (VAF) sensor high input Wiring short to positive, MAFNAF sensor, ECM

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What Does Code P0103 Mean?

The troublecode P0103 is set when the MAF sensor signal is consistently high.  This code, unlike P0102, is not often encountered.

When diagnosing MAF sensor codes, understanding fuel trims is very important.  Please see the fuel trims article (P0171):

Fuel Trims – Lean

Identifying the type of MAF sensor in your car will also aid diagnosis.  There are a number of different MAF sensors including the most common hot-wire sensors.  The following Youtube video describes vane, analog or digital hot-wire, and vortex MAF sensors:

Note: Circuit High Input codes are mostly caused by defective alternators that develop excessive voltages, although there may be other causes as well, such as short circuits that “leak” current into a particular system from other, unrelated systems that work on higher voltages. Note that in the case of short circuits that leak power into a control circuit, there is likely to be other, seemingly unrelated trouble codes present along with the code(s) being investigated. Diagnosing a “high input” code will always involve a thorough testing of the charging system as a first step, followed by measures to isolate the system from all other possible sources of power during resistance, continuity, and reference voltage tests.



What are the common causes of code P0103 ?

The P0103 is not a common code.  A high frequency or high voltage MAF sensor signal, unlike related code P0102, does not indicate a dirty MAF.  The code is also unlikely a PCM problem.  The cause can be some sort of wiring issue.  You should trace the wiring to the MAF and see if another power source is interfering with the MAF’s signal.

What are the symptoms of code P0103 ?

The ECU will also illuminate the MIL (malfunction indicator lamp), also referred to as the CEL (check engine light), though you may not notice any drivability issues. Still, aside from the MIL, some common symptoms may include difficulty starting, poor idle quality, or lack of power. Additionally, since the MIL indicates that the ECU is now running the engine in open-loop “limp home mode,” you may also notice poor fuel economy.

How do you troubleshoot code P0103 ?

In the intake air stream, the MAF is located somewhere between the air filter box and the intake manifold, some models placing the sensor right on the air filter box, and others in the intake hose. Depending on if the MAF has an integrated IAT (intake air temperature) sensor, it may have between four and seven wires coming out of it. The following troubleshooting steps should be taken to confirm failure and make a proper repair.

  1. If you can save or print freeze frame (FF) data, taking note of important FF data points, such as RPM, vehicle speed, and gear position. Try to recall driving conditions, as well as any recent maintenance or repairs, when the MIL came on the first time. All of these can give you clues as to when the problem is occurring. Concurrent DTCs should also be noted, especially if they are related to the Fuel and Air Metering System, such as P0171 or P0111.
  2. Clear the DTC, shut the engine off, then turn the ignition to KOEO (Key ON, Engine OFF) position.
    1. If the same DTC comes back immediately, chances are that you have a hard fault, perhaps a broken wire, dead sensor, or unplugged sensor. If this is the case, take a look at the connector and wiring going to the MAF.
    2. Unplug the MAF and inspect the connector for corroded or damaged pins or sockets.
    3. If the same DTC doesn’t come back on KOEO, the sensor internals and wiring are probably electrically sound.
  3. If the KOEO test doesn’t illuminate the MIL, start the engine and leave it idling.
    1. If MIL illuminates during the KOER (Key ON, Engine RUNNING) test, with the same DTC, suspect the MAF sensing portion of contamination or blockage. Take out the MAF and inspect it with a flashlight. Blow out any dust or debris which may be blocking the sensing portion. If you suspect oil contamination or similar, you can attempt to clean it in a bath of isopropyl alcohol (90% or better), electrical contact cleaner, or MAF sensor cleaning spray. Do not attempt to brush or scrub the sensing portion, as it can be extremely fragile. Even so, excessive contamination may be impossible to clean, even after multiple applications, and replacement may be the only option.
    2. A concurrent fuel trim DTC, such as P0171, may point to an intake leak or vacuum leak. In either of these cases, more air is getting into the engine than the MAF and ECU can properly account for. Look for loose or cracked vacuum lines, including those to the vacuum brake booster or power steering idle-up switch. Also check the intake air hose after the MAF, making sure there are no holes or cracks.
  4. If the KOER test is inconclusive, taking the car for a test drive may be necessary. If you were able to glean any important information from the FF data, try to reproduce the driving conditions during which the fault was detected. Lack of power and an illuminated MIL on hard acceleration might point to a cracked intake hose, for example.

Codes Related to P0103

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