P2226: Barometric Pressure Sensor A Circuit
What to do
The car will usually drive, with fuelling that is slightly wrong and gets more wrong the further you are from sea level. Ask which sensor actually supplies the barometric reading on your engine — on most, it is the manifold pressure sensor read at key-on rather than a separate part, so a "barometric pressure sensor" may not exist to replace. Mention any connection with altitude: running badly on a mountain trip and better at home, or the reverse, is exactly what this fault looks like and is not something a workshop can observe.
What this code means
A fault in the barometric pressure measurement. The first thing to establish is whether the vehicle has a barometric pressure sensor at all, because on a great many engines it does not — and people have bought parts that were never fitted.
What the measurement is for. Barometric pressure is, in practice, an altitude measurement. Air thins as you climb, so the same volume contains less oxygen, and an engine that goes on delivering sea-level fuelling at altitude runs progressively rich. The module needs a reference for how dense the air is before it can interpret anything else it measures, and this is that reference.
Where the reading usually comes from. Rather than fit a dedicated sensor, most engines read the manifold absolute pressure sensor at a moment when manifold pressure is known to equal atmospheric — with the ignition on and the engine not yet running, when the throttle is closed but nothing is drawing a vacuum. Some also refresh the value at wide-open throttle, where manifold pressure again rises close to ambient.
That one design decision explains most of what is confusing about this code:
- A MAP sensor fault produces a barometric pressure code, because they are the same sensor doing two jobs. Expect P0106 or P0107 alongside, and treat the MAP sensor as the part.
- The reading is a snapshot, not a continuous measurement. A vehicle driven a long way uphill without being switched off may be running on a barometric value taken at the bottom.
- There may be nothing to replace. Asking which sensor supplies the value on this engine is the first question, not a detail.
The symptom pattern is altitude-dependent and worth reporting. A car that runs correctly at home and poorly in the mountains, or that arrived at a hill station running badly and improved on the way down, is describing this measurement rather than a general fuelling fault. That is information no scan tool will produce, and it points straight at the right system.
Likely causes
Start here
Less common
- Faulty barometric pressure sensor · easy
- Damaged wiring harness · moderate
- Failed sensor reference voltage supply · moderate
- Blocked or leaking vacuum hose to the sensor · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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