P0103: The mass airflow sensor is reporting a signal that stays too high
Mass air flow (MAF) sensor circuit high input
Severity: Monitor
A high MAF signal is a sensor-circuit fault; TroubleCodes.net lists poor idle, lack of power and poor economy as the effects, so it is worth getting checked soon but not an immediate danger by itself.
P0103 in short
P0103 means the mass airflow sensor signal is staying higher than it should. The usual causes are a wiring short to power, a failed MAF sensor, or a charging system putting out too much voltage. A dirty sensor is an unlikely cause. The car often drives in a reduced mode with poor economy.
The mass airflow (MAF) sensor measures the air entering the engine, and the engine computer uses that number to set fuel. P0103 sets when the sensor's signal is consistently higher than the computer considers believable.
TroubleCodes.net says this is an uncommon code and not usually a dirty-sensor problem. It points instead to a wire shorted to positive voltage, a defective sensor, computer trouble, or an alternator putting out excessive voltage that leaks into the circuit.
With the signal untrusted, the engine may run in a fallback mode, which is why hard starting, poor idle, weak power and poor fuel economy are the listed effects.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Wiring shorted to positive voltage at the MAF circuit
Common general cause- Why it ranks here
- TroubleCodes.net lists a wiring short to positive first, because the code means the signal is pinned high.
- What would change this
- A harness that tests as shorted to power raises it; clean wiring lowers it.
Cause 2: Defective mass airflow sensor
Common general cause- Why it ranks here
- A failed sensor is listed as a direct cause, though the page stresses a merely dirty sensing element is unlikely to set this code.
- What would change this
- A sensor that gives a high output at known-good voltage and wiring raises it.
Cause 3: Alternator putting out excessive voltage
Possible — needs testing- Why it ranks here
- TroubleCodes.net says to test the charging system early because an over-voltage alternator can feed the circuit.
- What would change this
- A charging voltage above specification raises it; normal voltage lowers it.
Cause 4: Engine computer fault
Possible — needs testing- Why it ranks here
- The computer is listed as a possible cause, but only after the sensor, wiring and charging system test good.
- What would change this
- Only consider it after every other test passes.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read the stored codes and freeze-frame data and note the driving conditions when P0103 set.
IfOther airflow, fuel trim or charging codes are stored too
It meansTreat the other codes as part of the same problem.
IfP0103 is the only code
It meansMove on to the sensor and connector.
Step 2: Look at the MAF connector for corrosion or damage and check the sensing element for contamination.
IfThe connector is corroded or damaged
It meansRepair it and see whether the code returns.
Points to: Wiring shorted to positive voltage at the MAF circuit
IfThe connector and element look fine
It meansTest the circuit and charging voltage.
Step 3: Measure battery voltage with the engine running and have the MAF signal and wiring checked for a short to power.
Warning:Probing a running engine bay puts hands near the fan belt and hot parts. Keep clear of moving parts and do not short the connector pins.
IfCharging voltage is above specification
It meansThe alternator is a likely cause.
IfCharging is normal and the wiring is shorted to power
It meansRepair the wiring.
Points to: Wiring shorted to positive voltage at the MAF circuit
IfCharging and wiring are normal but the signal stays high
It meansThe sensor is suspect.
Symptoms
- Check engine light
- Hard starting
- Poor idle quality
- Lack of power
- Poor fuel economy
Compare with: Rough idle with the check engine light on, Check engine light with loss of power
How to fix
Step 1: With the engine off, check that the MAF sensor connector is fully seated and free of corrosion.
Step 2: Ask a shop to test the charging voltage before replacing the sensor.
Parts and cost context
- Mass airflow (MAF) sensor:Test the wiring and charging voltage before replacing the sensor. Labour varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for P0103 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0103 yet.
All Air metering (MAF, MAP and intake air temperature) codes
P0103 questions
Will cleaning the MAF sensor fix P0103?
Probably not. TroubleCodes.net says this code is unlikely to come from a dirty sensor and points to wiring, the sensor itself, charging voltage or the computer.
Can a bad alternator cause P0103?
It can. TroubleCodes.net lists an alternator with excessive output voltage as a cause and says to test the charging system early.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error