OBD-II Fault Code

P0109: Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0109.

System family

Powertrain

Generic/SAE

Repair category

Air / load sensor

Use this category to narrow your checks before replacing parts.

Severity

Medium

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What P0109 usually means

Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent.

Common symptoms

Check Engine light; Poor drivability or reduced fuel economy depending on fault

Likely causes

Faulty MAP sensor; Vacuum hose leak/blockage; Wiring/connector fault; Loose connector; Moisture/corrosion; Harness vibration fault

Diagnostic checks

Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Compare MAP reading key-on-engine-off to barometric pressure; Inspect vacuum port/hose and wiring; Wiggle-test harness while watching live data; Inspect for water intrusion/corrosion

Repair guidance

Clean blocked port, repair hose/wiring, replace sensor if confirmed faulty; Clean/secure connector and repair damaged harness

Verification after repair

Clear code, road-test through the same drive condition, then rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary. A DTC identifies a circuit or system condition, not always the failed part.