OBD-II Code · Sensors
P0109
MAP/BARO Sensor Circuit Intermittent
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$80–$250
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Intermittent MAP signal.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Intermittent CEL
- Rough idle occasionally
Likely causes
- Loose connectorMost common
- Chafed wiring
- Failing sensor
Read the full diagnostic procedureP0109 is the intermittent MAP code — the ECM saw an out-of-range MAP signal that recovered before latching a P0107 or P0108, and it has happened enou…
P0109 is the intermittent MAP code — the ECM saw an out-of-range MAP signal that recovered before latching a P0107 or P0108, and it has happened enough times to set a code. Like P0104 for MAF, these are diagnosis-heavy because the fault is rarely present in the bay.
Cheapest-first ladder
- wiggle-test the MAP connector and the 6-12 inches of harness behind it with engine running and a scan tool recording MAP kPa — any spike from 35 kPa idle to 100 kPa, or drop to 0 kPa, confirms the fault zone; inspect the connector for pushed-back terminals and oil contamination (oil in the connector body is a leading cause of intermittent MAP signal on Chrysler Hemi and GM trucks); check the vacuum reference hose for a partial restriction that intermittently clears — a wad of carbon that sits in the port and gets blown clear at high RPM will set P0109 repeatedly; clean the MAP port with carb cleaner if the engine is direct-injection because carbon partial blockage is the most common P0109 cause on VW/Audi, BMW, and Ford EcoBoost; leave a scan tool recording freeze-frames during the customer's normal drive cycle if bay-side testing comes up clean.
- Replacing the MAP for P0109 without a wiggle test and a vacuum-port inspection is the most common misdiagnosis in this code — the sensor is usually fine.
Vehicle-specific patterns2008-2014 VW/Audi 2.0T TSI sets P0109 from partial carbon blockage of the MAP port that clears and re-blocks with engine vibration; 2005-2010 Chrysle…
- 2008-2014VW/Audi 2.0T TSI sets P0109 from partial carbon blockage of the MAP port that clears and re-blocks with engine vibration;
- 2005-2010Chrysler 5.7L Hemi sees P0109 from oil contamination wicking into the MAP connector intermittently shorting the signal pin;
- 2007-2014GM 5.3L sees P0109 from the under-intake MAP picking up intermittent moisture from a slow intake gasket coolant weep;
- 2007-2018Cummins 5.9L/6.7L Ram sees P0109 from soot intermittently bridging the MAP signal circuit before fully clogging the port.
Estimated repair$30 to $450.
Look up another code
P0109 — frequently asked
What does a P0109 code mean?
Intermittent MAP signal.
What causes a P0109 code?
Common causes: Loose connector; Chafed wiring; Failing sensor.
What are the symptoms of a P0109 code?
Typical symptoms: Intermittent CEL; Rough idle occasionally.
Is it safe to drive with a P0109 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $80-$250.
How do I diagnose a P0109 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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