P2228 Code: Barometric Pressure Circuit Low
The baro sensor signal is below its valid range, as if the car were far higher than any road goes.
At a glance
Severity: Moderate
- Meaning
- Barometric Pressure Circuit Low
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $80–$1,600
- DIY difficulty
- Hard
P2228 means the barometric pressure signal dropped below the lowest voltage or value the ECM accepts. On a separate three-wire baro sensor that nearly always means an electrical fault: the 5 V reference is open or pulled down, the signal wire is shorted to ground or broken (many ECMs pull an open signal low), or the sensor itself has failed low. On the many vehicles where the baro sensor is built into the ECM, a low circuit code usually points to the ECM, after supply and ground have been checked. The effect on the engine is the opposite of what you might expect: a very low baro value tells the ECM the air is extremely thin, so it may cut boost, derate the engine and change fueling, until it switches to a fixed substitute value. That's why P2228 often comes with a noticeable loss of power while the related circuit code P2226 frequently goes unnoticed.
Can I keep driving? The car will usually drive, but possibly with reduced power and boost. Avoid merging onto fast highways or passing where you'd need full power, and have it looked at soon.
How to read P2228
- P Powertrain
- 2 Generic (SAE)
- 2 Fuel & air (injector circuit)
- 28 Specific fault
Symptoms
- Check engine light with reduced power or a 'reduced engine power' message
- Turbo engines making noticeably less boost
- Baro reading on the scan tool near zero or at an impossible altitude value
- Several sensor codes at once if a shared 5 V reference is shorted
- Occasional hard starting or rough running before the substitute value kicks in
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Internal baro sensor failure on vehicles with the sensor built into the ECM
- 5 V reference open or shorted to ground, often by another sensor on the same supply
- Signal wire shorted to ground or broken
- External baro sensor failed low
- Water in the ECM or sensor connector
- Very low system voltage or a poor ECM ground
Diagnosis step by step
Check the baro value against the real world
Read baro with the key on. In the US, anything below roughly 8.5 psi (about 59 kPa) is lower than the air pressure on the highest paved road in the country, so it's a circuit fault, not altitude. Note whether MAP reads normally at the same time.
Tools: OBD-II scanner
Look for a shared 5 V problem
If P0641, P0651 or low-voltage codes for other sensors are stored, the 5 V reference feeding the baro sensor is probably shorted. Unplug the sensors on that circuit one at a time with the key on; when the reference voltage recovers, you've found the sensor or harness branch pulling it down.
Tools: OBD-II scanner, Multimeter
Measure reference and signal at an external sensor
Key on, sensor connected, back-probe: reference 4.8–5.2 V, ground under 0.1 V to battery negative, and the signal somewhere in the middle of the range for your elevation. A signal near 0 V with good reference and ground points at the sensor or a shorted signal wire.
Tools: Multimeter
Do the jumper test
Unplug the sensor and briefly jumper the signal pin to the 5 V reference at the harness side with a fused jumper. The baro reading should jump to its maximum (and may set a high code); if it does, the wiring and ECM are fine and the sensor is bad.
Tools: Multimeter, Pliers
Check for a short to ground
With the ECM and sensor unplugged, measure between the signal wire and chassis ground; it should read open. Any low resistance means a chafed or pinched wire, commonly where the harness passes brackets or the engine lifting eye.
Tools: Multimeter
Internal sensor: verify power, then ECM
If the sensor is inside the ECM, confirm all ECM power and ground pins under load and look for water in the connectors. With those good and no update available, the ECM needs replacing and programming.
Tools: Multimeter, OBD-II scanner
Where the parts are
- 1Upstream O2 sensor
- 2Catalytic converter
- 3Downstream O2 sensor
- 4Diesel particulate filter
- 5Turbocharger
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair shorted or broken signal or reference wire | No | $100–$350 |
| Replace the sensor that shorts the shared 5 V reference | Yes | $80–$350 |
| Replace external baro sensor | Yes | $100–$300 |
| Replace and program ECM (internal sensor) | 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
P2228 turns on the check engine light, which fails OBD-based emissions inspections in states that test. Readiness monitors must also be complete after the repair, so allow a few days of normal driving.
Frequently asked questions
Why does a low baro reading cost power?
A very low value tells the ECM the air is extremely thin, as if you were high in the mountains. To protect the turbo and engine it reduces boost and adjusts fuel, which you feel as a loss of power.
What's the difference between P2228 and P2226?
P2226 is a general circuit fault. P2228 says specifically that the signal is too low, which narrows it down to a short to ground, an open reference or signal, or a sensor that has failed low.
Can a bad MAP sensor cause P2228?
Indirectly, yes, if it shares the 5 V reference with the baro sensor and shorts it. That's why other sensor codes stored at the same time are an important clue.
Is it safe to keep driving?
For short trips, usually. The reduced power can be a problem when merging or passing, so don't rely on full acceleration until it's fixed.
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