Mass Airflow Sensor
2021 Honda Accord · 1.5L I4 Turbo
Sensor Type
hot-wire
Waveform Type
dc-variable
Location
Integrated into air intake tube between air filter box and turbocharger inlet, passenger side of engine bay
Pins
5-pin connector
Timebase
100ms/div
Voltage Scale
1V/div
Trigger
N/A - DC signal
Wiring
Yellow (12V power from PGM-FI relay), Black (sensor ground), Red/Black (signal output to ECM), Green (intake air temperature sensor signal), Brown (IAT ground)
Expected Voltage Range
At Idle
0.8V to 1.4V
At Higher RPM
3.2V to 4.8V
Expected Pattern
Smooth DC voltage that increases linearly with airflow, clean signal with minimal noise <50mV ripple
Known-Good Waveform
At idle, MAF outputs 0.9-1.3V corresponding to 2-4 g/s airflow on naturally aspirated mode. Under acceleration and boost, voltage rises smoothly to 3.5-4.5V (peak airflow 80-120 g/s under full boost). Signal should be extremely clean with less than 50mV ripple, responding immediately to throttle changes with no lag or hesitation.
Common Failure Patterns
Voltage stuck at 0.8-1.0V regardless of RPM or load, no response to throttle
Cause: Contaminated hot-wire element from oil residue or debris, broken sensing element
Signal shows excessive noise or oscillation >200mV, erratic voltage spikes
Cause: Cracked MAF housing causing turbulent airflow, damaged sensing element, or electrical interference
Diagnostic Tips
Honda 1.5T uses Denso hot-wire MAF highly sensitive to contamination from oiled aftermarket air filters. Common issue: PCV system draws oil vapor into intake causing MAF contamination and lean codes. Check for intake tube cracks between MAF and turbo. Verify voltage at idle matches Honda PID data for g/s airflow (typical 2.5-3.5 g/s warm idle).
Related Diagnostic Trouble Codes
P0100P0101P0102P0103P0104
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
Free, no signup. View all waveforms for this vehicle