How can I prove there is a fault when it tests fine at the shop?

Graph the value across a drive. Atmospheric pressure is the slowest-moving input on the vehicle — it takes hours to shift meaningfully, and altitude changes it smoothly along with the road. So the trace should be a nearly flat line. If it steps, spikes or looks noisy, that is not weather and it is not altitude; it is the circuit, and you have proved it without any reference specification. Very few sensors let you be that certain from the shape of a trace.

Why does it only act up when the weather is wet?

Because of where the sensor has to live. It measures outside air, so it is mounted where outside air is — behind a fender liner, in the air filter housing, on the firewall — which are the wettest places on the vehicle. Moisture in the connector creates a leak path that appears when damp and dries out on a warm workshop ramp. That is also why static testing so often comes back clean, and why sealing and reterminating the connector is frequently the whole repair.

The symptoms make no sense — sometimes it runs rich, sometimes lean. Is that one fault?

It can be exactly one fault, and the contradiction is characteristic. When the erratic reading goes high the module thinks the air is dense and adds fuel, so the engine runs rich and feels flat. When it goes low the module thinks the air is thin and pulls fuel, so it runs lean and surges. Same circuit, opposite symptoms on different days. Recognising that pattern is what stops a fuel pump or a transmission being blamed for it.

My logged drive was completely clean. Does that clear the sensor?

Not on its own. Modules know this signal is slow, so they filter it heavily and many only refresh the stored value at key-on and briefly at wide-open throttle, holding it in between. A real fault can sit through an entire drive without appearing and then show as a single step at the next start. Log several key-on events, and a wide-open throttle pull if the road allows, before concluding the circuit is healthy.

OBD-II trouble code

P2230: Barometric Pressure Circuit Intermittent/Erratic

Atmospheric pressure is the slowest-moving input on the vehicle, so any movement inside one drive is proof of a fault by itself. That makes this the one code in the family you can confirm from a graph — and the sensor's exposed mounting means the pattern usually follows the weather.

Medium severityPowertrainFuel & Air MeteringDrivable short-term

Quick facts

System: Powertrain
Category: Fuel & Air Metering
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $60 – $700
DIY difficulty: Intermediate DIY

What does P2230 mean?

There is a property of this particular signal that makes an otherwise awkward fault unusually easy to prove, and it is worth putting first because it saves buying anything on suspicion.

Barometric pressure is the slowest-changing quantity a control module measures. Coolant temperature moves in minutes, manifold pressure moves in milliseconds, but atmospheric pressure takes hours to shift meaningfully, and even a fast-moving weather front changes it far more slowly than a car can be driven. The only thing that moves it quickly is altitude, and that movement is smooth and follows the road. Which means a graph of this value over a single journey should be an almost flat line, gently sloping if you climbed a hill. Anything else — steps, spikes, a value that jumps and settles, a trace that looks noisy — is not the atmosphere doing something unusual. It is the circuit misbehaving, and it is visible without any specification to compare against. On no other input can you be that certain from the shape of the trace alone.

The second thing worth knowing is where these sensors live, because it explains the pattern most owners describe. A dedicated barometric sensor has to sample outside air, so manufacturers put it where outside air is: behind a fender liner, in or on the air filter housing, on the firewall, occasionally inside a wheel arch. Those are the wettest locations on the vehicle. This is the one code in the barometric family whose intermittents correlate with water rather than with heat — it appears after rain, after a car wash, after driving a flooded road, and then goes away for a fortnight of dry weather. Ask about that history directly. An owner who says it always seems to happen when it is wet has told you more than an hour of probing will.

That weather correlation also explains why a static test so often comes back clean. Moisture in a connector creates a resistive leak path that dries out on a warm ramp, and by the time the vehicle is on a lift with the connector in your hand, the evidence has evaporated. The productive approach is recorded rather than probed. Read the freeze frame first — it captures conditions at the moment the code set, and on this code the useful fields are ambient temperature and vehicle speed rather than engine load. Then log the barometric value across a real drive, ideally in the conditions the owner associates with the fault, and look for the steps that atmospheric pressure cannot make.

One complication to expect. Modules know this signal is slow, so they filter it heavily and many only refresh the stored value at key-on and again briefly at wide-open throttle, holding it between times. A fault can therefore be present for an entire drive without appearing in the data, and then show up as a single step at the next key-on when the module finally looks. If a logged drive is clean, log several key-on events instead, and include a wide-open throttle pull if the vehicle and the road allow it.

The driveability picture is genuinely confusing, and it is worth warning the owner about it. Because the wrong value comes and goes, the symptoms come and go with it and they point in opposite directions on different days — rich and flat when the reading is high, lean and surging when it is low, and perfectly normal in between. Complaints get attributed to the fuel pump, the transmission, bad fuel or the weather itself, and vehicles get parts fitted for problems they do not have. Recognising that an intermittent barometric fault produces contradictory symptoms is what stops that spiral.

Common causes

Water or condensation intruding into the sensor connector, which is mounted in one of the wettest positions on the vehicle
Corroded terminals producing a resistive path that appears when damp and disappears when dry
Chafed signal wire making occasional contact with a bracket, body seam or the reference conductor beside it
Failing sensor with an internal fault that appears under vibration or thermal change
Loose or vibrating connector that has lost latch tension and moves with road inputs
Intermittent five-volt reference or ground affecting several sensors at once
Damaged harness after fender liner, bumper, air intake or washer system work in the same area
Sensor element contaminated by water ingress into the air filter housing on applications mounted there
Manifold absolute pressure sensor circuit fault on vehicles that derive the barometric value rather than fitting a dedicated sensor

Symptoms

Check engine light that comes and goes, sometimes clearing itself for weeks at a time
Symptoms that contradict each other on different days — rich and flat on one occasion, lean and surging on another
A pattern that follows the weather, appearing after rain, a car wash or a flooded road
Inconsistent fuel economy with no change in how the vehicle is driven
Occasional hesitation, surging or a brief loss of power that does not repeat on demand
A logged barometric trace showing steps or spikes that atmospheric pressure is physically incapable of producing
Boost behaviour on turbocharged engines that varies between drives
Emissions readiness monitors that will not reliably complete

Diagnostic steps

1.Read the freeze frame first and note ambient temperature and vehicle speed rather than engine load, since this fault is about conditions rather than about what the engine was doing.
2.Ask the owner directly whether the fault tracks wet weather, car washes or a particular road. A weather correlation points at the connector and shortens the job considerably.
3.Log the barometric value across a full drive and look at the shape of the trace. Atmospheric pressure cannot step or spike, so any discontinuity is proof of a circuit fault with no specification lookup required.
4.If a logged drive is clean, capture several key-on events and a wide-open throttle pull instead, because many modules only refresh this value at those moments and hold it in between.
5.Locate the sensor and assess its exposure — behind a fender liner, in the air filter housing or on the firewall — and inspect for standing water, silt and salt at the connector.
6.Open the connector and look for green corrosion and water staining, checking terminal tension against an undisturbed cavity.
7.Wiggle-test the harness and connector with live data displayed, and if the fault has a wet-weather history, try reproducing it with a light water spray on the connector area rather than waiting for rain.
8.Measure the five-volt reference and ground while flexing the harness, since an intermittent supply affects every sensor on that group and shows up as several codes appearing together.
9.Where nothing is reproducible, seal and reterminate the connector as the highest-probability repair and re-log rather than fitting a sensor on suspicion.

Repair cost

$60 – $700

Diagnostic time runs higher than the rest of this family, $120 to $300, because confirming an intermittent generally needs logged drives and sometimes a vehicle left with a logger fitted. Cleaning, reterminating and properly sealing a water-contaminated connector is $80 to $300 and is the most common successful repair on this code. A standalone barometric sensor is $30 to $190 in parts, $60 to $250 fitted. Repairing a chafed or intermittently shorting harness section runs $150 to $500 depending on access behind liners and ducting. Where the value is derived from the manifold pressure sensor, budget $80 to $350 fitted for that sensor instead.

Estimate your repair

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Open the Repair Cost Estimator with barometric pressure sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.