Manifold Absolute Pressure (MAP) / Barometric Pressure Circuit Intermittent
The P0109 code means the vehicle's onboard diagnostic system has detected: Manifold Absolute Pressure (MAP) / Barometric Pressure Circuit Intermittent. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $30 - $300 (MAP sensor $30-$150; wiring repair $50-$100; labor $50-$150)
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Common Symptoms
- Check Engine Light on, may come and go
- Intermittent engine surging or hesitation
- Erratic idle speed
- Inconsistent acceleration response
- Engine may stall unpredictably
Probable Causes (Ranked by Likelihood)
- Loose or corroded MAP sensor connector Very High
- Intermittent vacuum leak in the hose to the MAP sensor High
- Damaged wiring with intermittent contact Moderate
- Failing MAP sensor with intermittent output Moderate
- Loose MAP sensor mounting causing vibration-related dropouts Low
Frequently Asked Questions
Can I drive with code P0109?
You can drive short distances, but intermittent MAP sensor signals cause unpredictable engine behavior. The engine may surge, hesitate, or stall without warning, making it unreliable in traffic.
Why does the code come and go?
Intermittent codes are caused by connections that work sometimes and fail other times. Common causes include loose connectors, cracked vacuum hoses that only leak when hot, or damaged wires that lose contact during vibration.
How do I diagnose an intermittent fault?
The key is to reproduce the failure. Use a scan tool to monitor MAP voltage in real time while wiggling connectors, flexing hoses, and tapping the sensor. The signal will drop or spike when the intermittent fault occurs.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Inspect the MAP sensor connector for loose, corroded, or bent pins. Wiggle the connector while monitoring MAP voltage on a scan tool to check for signal dropouts.
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Check the vacuum hose to the MAP sensor. Flex it along its length while watching sensor readings. A cracked hose may only leak under certain conditions.
-
Monitor MAP sensor voltage while tapping on the sensor. If the reading fluctuates, the sensor has an internal intermittent fault.
-
Inspect the wiring harness for chafed insulation or broken wire strands that could make and break contact with engine vibration.
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Verify the MAP sensor is securely mounted. A loose sensor can vibrate and cause intermittent connection issues at the connector.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- 2003-2014 Dodge Ram 1500 (5.7L HEMI)
- 2006-2015 Jeep Wrangler (3.8L, 3.6L)
- 2005-2013 Chrysler 300 (5.7L)
- 2008-2016 Honda Civic (1.8L, 2.0L)
- 2007-2015 Hyundai Elantra (1.8L, 2.0L)
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