Manifold Absolute Pressure Sensor
2021 Honda Accord · 1.5L I4 Turbo
Sensor Type
piezoresistive
Waveform Type
dc-variable
Location
Mounted on intake manifold on passenger side of engine, integrated into manifold or connected via vacuum line to manifold plenum
Pins
3-pin connector
Timebase
200ms/div
Voltage Scale
1V/div
Trigger
N/A - DC signal
Wiring
Green/White (5V reference from ECM), Green/Black (signal output to ECM), Brown/Black (sensor ground)
Expected Voltage Range
At Idle
0.9V to 1.4V
At Higher RPM
4.1V to 4.7V
Expected Pattern
Smooth DC voltage reflecting manifold pressure: 0.9-1.4V at idle (high vacuum), rising to 2.3-2.5V at atmospheric, 4.2-4.6V under boost
Known-Good Waveform
Key-on engine-off (KOEO) shows 2.3-2.5V representing barometric pressure at sea level. At warm idle, voltage drops to 0.9-1.3V reflecting intake vacuum of 16-20 inHg. Under turbo boost, voltage rises smoothly to 4.2-4.6V representing 14-18 PSI boost pressure. Signal must be rock-steady with less than 30mV noise and respond instantly to throttle changes.
Common Failure Patterns
KOEO voltage below 2.0V or above 3.0V, doesn't match barometric pressure
Cause: Failed MAP sensor silicon diaphragm, internal reference chamber leak, or 5V reference voltage problem
Voltage stuck around 2.4V with minimal change between idle and boost conditions
Cause: Restricted vacuum line or fitting, blocked sensor port, or failed sensor element
Signal fluctuates excessively or shows irregular spikes during boost
Cause: Boost control system malfunction, wastegate issue, or blow-off valve leak causing erratic pressure
Diagnostic Tips
The 1.5T MAP sensor is critical for boost control and fuel/timing calculations. Verify 5V reference is stable as shared circuit issues affect multiple sensors. Common problem: charge air cooler end tank cracking causing boost leaks - MAP will show lower boost voltage than commanded. Compare actual boost pressure with scan tool PIDs during wide-open throttle test (should reach 18-20 PSI).
Related Diagnostic Trouble Codes
P0105P0106P0107P0108P0109
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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