P0102 - Mass or Volume Air Flow Circuit Low Input
System
Powertrain (Engine & Gearbox)
Technical Description
The Engine Control Module (ECM) detects that the MAF sensor signal voltage or frequency output is below the minimum calibrated threshold (typically < 0.2V or < 500 Hz), indicating an open signal line or short circuit to ground.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Signal Wire Voltage (Fault State) | Voltage (V) | < 0.20 V (Normal: 0.8 - 4.5 V) | Ignition ON |
| Sensor Main Power Feed | Voltage (V) | 11.8 - 14.4 V | Pin 2 to chassis ground |
| Ground Circuit Resistance | Resistance (Ω) | < 0.5 Ω | Sensor ground to engine block |
Ignition ON
Pin 2 to chassis ground
Sensor ground to engine block
Oscilloscope Waveform Analysis
500 ms/div, 1 V/divPossible Causes
Short to ground or open circuit on signal wire between MAF and ECM
Internal component failure inside the MAF sensor electronics
Blown EFI/engine management fuse supplying sensor power
Water intrusion or severe terminal pin corrosion in connector
Symptoms
Recommended Solution
Disconnect MAF harness and measure 5V reference and 12V supply with ignition ON.
Measure signal wire resistance to ground to detect short circuits.
Check continuity (< 1.0 Ω) from sensor connector to ECM harness connector.
Replace MAF sensor if wiring harness integrity and supply voltages verify good.
Mechanic's Tip
Diagnostic trick: If unplugging the MAF causes the signal circuit voltage to rise to 5.0V (ECU pull-up bias), the wiring and ECM are 100% verified intact, proving the sensor itself is shorted internally.