P0109
UniversalManifold Absolute Pressure/Barometric Pressure Circuit Intermittent
The engine computer monitors pressure information from the manifold absolute pressure (MAP) and/or barometric pressure circuit to help calculate engine load and manage fueling and ignition. This code means that signal has been intermittent. The cause could be a sensor, wiring, connection, or another issue affecting the signal; the code alone does not prove a particular part has failed. Some vehicles may run poorly, while others show no noticeable symptoms.
⚠️ Before You Begin (Safety First)
If the engine stalls, loses power, or becomes difficult to control, pull over safely and stop driving; arrange diagnosis or towing if needed. If the vehicle runs normally, arrange inspection soon and watch for worsening symptoms.
Common Symptoms
- The check-engine light may be on, with no noticeable change in how the vehicle drives.
- Hesitation or uneven acceleration may occur if intermittent pressure information disrupts engine load calculations.
- Rough running or stalling may occur if the engine computer receives inconsistent pressure data.
- Fuel economy or emissions performance may worsen if fueling or ignition control is affected.
Common Causes
- A loose, damaged, or corroded connector may interrupt the pressure-sensor circuit intermittently.
- Wiring damage, chafing, or an intermittent internal wire break may cause the signal to drop out.
- The MAP or barometric pressure sensor may have an intermittent internal fault.
- A problem with the circuit's power supply or ground may make the signal unstable.
- Where applicable, a restricted or damaged pressure passage or hose may contribute to inconsistent pressure readings.
Diagnostic Steps
- Note whether the engine is running poorly, stalling, or showing other warning lights; stop driving if it becomes unsafe to control.
- With the engine off and cool, visually inspect accessible sensor connectors and wiring for looseness, corrosion, chafing, or damage. Do not pull or probe wiring forcefully.
- If a connector is visibly loose, ensure it is seated correctly without forcing it; have damaged or corroded connections repaired appropriately.
- If you have a scan tool, record other codes and available freeze-frame information before clearing anything; related data can help identify when the signal became intermittent.
- Have a qualified technician perform vehicle-specific circuit and sensor tests if the code returns or symptoms continue. Avoid replacing parts based on the code alone.
When to Call a Professional
A technician can review stored and pending codes and freeze-frame data, then monitor MAP/barometric pressure data for dropouts. Inspection and model-specific testing of the sensor circuit, connectors, wiring, power supply, and ground can help distinguish a sensor fault from a circuit or pressure-path issue. Exact test procedures depend on the vehicle.
Compare component listings
Confirm diagnosis and vehicle fitment before buying. A listing does not prove that a part needs replacement. We may earn a commission from qualifying purchases.
Commonly Asked Questions
Does P0109 prove the MAP sensor needs replacement?
No. It identifies an intermittent MAP/barometric pressure circuit condition. A sensor, connector, wiring, power supply, ground, or applicable pressure path may be involved, so testing is needed before replacing parts.
Can I keep driving with P0109?
It depends on how the vehicle behaves. If it stalls, loses power, or becomes difficult to control, stop in a safe place and do not continue driving. If it runs normally, arrange diagnosis soon and monitor for worsening symptoms.
What does the MAP or barometric pressure information do?
The engine computer uses pressure information to estimate engine load and help manage fueling and ignition. An intermittent signal can make those calculations less reliable.
What is the first useful diagnostic check?
Check for other codes and review available freeze-frame or live data, then inspect accessible connectors and wiring. A technician can use vehicle-specific procedures to determine whether the sensor or its circuit is responsible.
Related Diagnostic Video
Browse Available Code Guides
Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.