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
3
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.