What Does P0109 Mean?
The manifold absolute pressure sensor circuit is producing intermittent or erratic signals. The PCM detects rapid, unexpected voltage fluctuations that don't correspond to normal changes in manifold pressure. This causes unpredictable fuel delivery and ignition timing adjustments. The driver may notice intermittent surging, stumbling, hesitation, or fluctuating idle that comes and goes.
Common Causes
35%
Loose or corroded MAP sensor connector with intermittent contact
25%
Damaged or chafed wiring in the MAP sensor circuit
15%
Cracked vacuum hose that opens and closes with engine temperature or vibration
15%
Failing MAP sensor with intermittent internal component failure
10%
Intermittent vacuum leak from a loose hose connection or cracked intake fitting
Diagnostic Steps
1
Monitor the MAP sensor PID in graphing mode at idle — the signal should be stable with minor fluctuations; erratic jumps of more than 5 kPa indicate an intermittent issue.
2
Wiggle the MAP sensor connector and wiring while watching the PID — any spike or dropout during wiggling identifies the fault location.
3
Inspect the MAP sensor connector for spread terminals, corrosion, or moisture — clean with electrical contact cleaner and apply dielectric grease.
4
Check the vacuum hose for hairline cracks, especially at the connection points — flex the hose while watching the MAP PID for sudden changes.
5
If no wiring or vacuum issue is found, tap lightly on the MAP sensor body while monitoring the PID — a change in reading indicates an internal sensor failure requiring replacement.
Estimated Repair Cost
$20 - $250
Parts + labor, varies by vehicle and location
The manifold absolute pressure sensor circuit is producing intermittent or erratic signals. The PCM detects rapid, unexpected voltage fluctuations that don't correspond to normal changes in manifold pressure. This causes unpredictable fuel delivery and ignition timing adjustments. The driver may not...
The most common cause of P0109 (Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent) is: Loose or corroded MAP sensor connector with intermittent contact
Typical repair costs for P0109 range from $20 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Generally safe to drive with occasional drivability hiccups. The intermittent nature means the engine usually runs fine. However, a sudden signal dropout during acceleration could cause momentary hesitation that might be concerning in traffic. Diagnose at your convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0109 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel / Air Metering System
Difficulty
Type
Generic (SAE)
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