Mass Airflow Sensor
2019 Toyota RAV4 · 2.5L I4
Sensor Type
thermistor
Waveform Type
dc-variable
Location
Air intake tube between air filter box and throttle body, approximately 8 inches downstream of air filter
Pins
4-pin connector
Timebase
500ms/div
Voltage Scale
1V/div
Trigger
N/A - DC signal
Wiring
Pink/Black (12V power), Brown (signal output to ECM), Black (ground), Yellow/Blue (intake air temperature signal)
Expected Voltage Range
At Idle
0.8V to 1.4V
At Higher RPM
3.5V to 4.8V
Expected Pattern
Steady DC voltage at idle around 1.0-1.2V, smooth linear increase with throttle opening and airflow increase
Known-Good Waveform
At idle with engine fully warmed, MAF signal should read 0.9-1.3V corresponding to approximately 2-4 g/s airflow. During snap throttle test, voltage should rise smoothly and immediately to 3.5-4.5V without hesitation, steps, or dropouts, then return smoothly to idle voltage. Signal should be clean with less than 50mV ripple at idle.
Common Failure Patterns
Voltage reading too low at idle (below 0.7V) or shows no change with throttle input
Cause: Contaminated hot-wire element from oil vapors or dirt, or circuit fault
Voltage reading too high at idle (above 1.6V) or erratic fluctuations
Cause: Vacuum leak downstream of MAF, damaged sensing element, or air filter housing leak
Diagnostic Tips
Toyota uses hot-wire MAF sensors that are sensitive to oil contamination from excessive PCV flow. Never use carburetor cleaner on element - use only MAF-specific cleaner. Compare MAF grams/second reading on scan tool to expected values: idle should be 2-4 g/s, 2000 RPM no load should be 6-10 g/s.
Related Diagnostic Trouble Codes
P0100P0101P0102P0103P0104
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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