P2227 Code: Barometric Pressure Circuit Range/Performance
The baro sensor's reading doesn't agree with the other pressure sensors or with what the engine is doing.
At a glance
Severity: Low
- Meaning
- Barometric Pressure Circuit Range/Performance
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- Yes, short term
- Typical repair cost
- $30–$1,600
- DIY difficulty
- Moderate
P2227 is a correlation code. The baro circuit is electrically fine, but its value doesn't fit the rest of the picture. The most common check happens at key-on before the engine starts: with no airflow, the MAP sensor and any boost pressure sensor sit at ambient pressure, so all of them should read the same as baro within a small margin. Some engines also compare baro with MAP at wide-open throttle on non-turbo engines, where manifold pressure comes close to ambient, or check whether baro changes at a believable rate while driving over hills. If the numbers disagree, the ECM can't tell which sensor is lying, so it sets P2227 even when the MAP or boost sensor is actually the faulty one. That makes comparing all the pressure readings side by side the heart of the diagnosis, before anyone orders an ECM or a sensor.
Can I keep driving? Generally safe to drive. Depending on which sensor is really wrong you may notice reduced power, especially at altitude or when towing, so have it checked before a mountain trip.
How to read P2227
- P Powertrain
- 2 Generic (SAE)
- 2 Fuel & air (injector circuit)
- 27 Specific fault
Symptoms
- Check engine light, frequently with a MAP or boost sensor code alongside
- Reduced power or boost, most noticeable at higher elevations
- Baro and MAP disagreeing at key-on engine off on the scan tool
- Slight changes in fuel economy or idle quality
- Code set after a rapid climb or descent, then not returning for days
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- MAP or boost pressure sensor drifting, making baro look implausible
- Built-in baro sensor inside the ECM drifting with age
- Clogged or oily MAP sensor port or hose, holding residual pressure or vacuum at key-on
- Blocked ECM vent or moisture inside the ECM housing
- Very restricted air filter or intake, making MAP fall short of baro at full throttle
- Software calibration issue with a known update
Diagnosis step by step
Line up all pressure readings at key-on
After the vehicle has been off for at least ten minutes, switch the key on without starting and read baro, MAP and boost pressure together. They should agree within roughly 0.3 psi (about 2 kPa); the one that stands apart is your suspect, regardless of which code was stored.
Tools: OBD-II scanner
Compare with the real station pressure
Check actual pressure where you are with a phone barometer app or the local airport's station pressure, not the sea-level-corrected number in weather reports. Denver, for example, sits around 12.1 psi while the TV forecast still shows about 30 inHg.
Tools: OBD-II scanner
Inspect the MAP sensor and its port
Remove the MAP or boost sensor and look for oil, soot or carbon in the port and the sensor nose; on engines with a remote MAP sensor, check the vacuum hose for cracks, kinks or trapped fluid. A partly plugged port can hold pressure long after the engine stops.
Tools: Screwdriver, Flashlight
Run the full-throttle check
On a non-turbo engine, a brief full-throttle pull at low rpm should bring MAP to within about 1 psi of baro. If MAP stays well below, a restricted air filter, collapsed intake duct or a sticking throttle is making the comparison fail.
Tools: OBD-II scanner
Check the ECM housing
Look at the ECM's vent membrane and connectors for dirt, water or corrosion, especially if the ECM sits low or near a cowl drain. A blocked vent lets the internal sensor read trapped pressure instead of the outside air.
Tools: Flashlight
Fix the outlier, then update
Replace or clean whichever sensor disagreed with the real ambient pressure, load any available calibration update, clear the code and repeat the key-on comparison. Only when the ECM's internal baro is proven wrong does the ECM need replacing.
Tools: OBD-II scanner
Where the parts are
- 1MAF sensor
- 2Turbocharger
- 3Throttle body
- 4Intake manifold
- 5Fuel injector
- 6EGR valve
- 7Fuel pump
- 8Thermostat
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean MAP sensor port or replace vacuum hose | Yes | $30–$120 |
| Replace MAP or boost pressure sensor | Yes | $90–$300 |
| Replace air filter or collapsed intake duct | Yes | $30–$150 |
| ECM software update | No | $100–$250 |
| Replace and program ECM (internal baro proven faulty) | No | $700–$1,600 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Will fail
A stored P2227 with the check engine light on fails OBD-based state emissions tests. After the repair, drive normally for a few days so all readiness monitors complete before the test.
Frequently asked questions
Can a change in the weather set P2227?
No. Weather shifts the pressure by a small amount and all the sensors see the same change, so they still agree. The code means one sensor disagrees with the others.
Why did it set after driving over a mountain pass?
Big, quick altitude changes expose a sensor that responds slowly or has drifted. The ECM sees baro and MAP moving differently and flags it, even though it may never happen on flat roads.
Should I replace the MAP sensor or the ECM?
Neither until you compare them with a trusted reference. Whichever one differs from the real station pressure is the faulty part; the MAP sensor is far more often the culprit and costs much less.
Does it hurt the engine to keep driving?
Not usually. The main effects are slightly wrong fueling and conservative boost, which cost some power and economy rather than causing damage.
Sources
- SAE J2012 – Diagnostic Trouble Code Definitions
- ISO 15031-6 – Road vehicles, diagnostic trouble code definitions (EOBD)
- Manufacturer public service information (cross-checked)
- Methodology: How We Build Code Pages · Data Sources We Use · Editorial Policy