Powertrain, generic · Fuel and air metering

P0103 Mass or Volume Air Flow Sensor A Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

The mass air flow sensor (MAF) sits between the air filter and the throttle or compressor and measures how much air the engine draws in; fuel quantity, load and ignition are calculated from it. Most are hot-film or hot-wire sensors that output either a voltage or, on GM, Saab and newer Ford systems, a frequency. P0103 means the signal is above its electrical upper limit. Documented limits: GM petrol 14,500 Hz or more, GM diesel above 12,500 Hz, Saab 9-4X above about 15,150 Hz, Ford analogue above 4.785 V (checked only below 4,000 rpm so that high load is not mistaken for a fault). Typical causes are a signal wire shorted to a voltage source, failed sensor electronics or interference from a harness routed too close to ignition coils, relays or motors. GM and Saab need two trips; the engine switches to a calculated air mass.

Likely causes

Signal wire shorted to voltage or to the supply wire
Sensor electronics failed
Interference from harness routed near ignition coils, relays or motors
Water in the connector or on the element

Symptoms

  • Check engine light on
  • Substitute value mode, lack of power
  • Rich mixture possible (smoke, consumption)
  • Rough idle, hesitation

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–300
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check wiring for chafing
  2. Measure signal with engine off and running
  3. Try a known-good sensor

Parts involved

mass air flow sensormass air flow sensor wiringsensor supply voltage

Related codes

P0100P0101P0102P0104P010D

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, newtonnet.co.uk.