P0105: Manifold Absolute Pressure - Barometric Pressure Circuit Malfunction

What P0105 tells you, and what it does not

On engines that use manifold absolute pressure to estimate engine load, this code sets when the sensor circuit signal is missing, frozen, or outside the electrical range the computer expects. It is an electrical fault rather than a value that is simply off.

The code sits in the manifold pressure sensor circuit area and is reported by the comprehensive component monitor. It names the circuit or the condition where the computer saw a reading outside its expected range. It does not name a failed part, and several genuinely different faults set this same code, which is the whole reason the causes below are ordered rather than listed.

What people usually notice

• Rough idle
• Hesitation on acceleration
• Stalling at idle
• Poor fuel economy

What causes P0105?

The causes below are ordered by how often they turn out to be the answer, cheapest and most common first. That order matters more than the list itself: the expensive component named in the code text is very rarely the first thing to replace, and working down from the top is what stops a manifold pressure sensor circuit fault becoming an expensive guess.

Disconnected or corroded connector at the sensor is the one to rule out before anything else. The simplest and most common cause to check first.

Working out which cause it is

Start with freeze frame. Manifold pressure and rpm at the fault show what the sensor was reporting at the moment of the fault. That snapshot is taken at the instant the code set, and it is the single most useful piece of evidence you have, which is also why clearing the code before reading it is such a costly habit.

This code is diagnosed by watching values change rather than by reading the number again, so the tool has to stream live data and hold freeze frame. Watching live manifold pressure against throttle position and rpm shows whether the signal is flatlined or simply implausible.

The order worth working in

• 1. Disconnected or corroded connector at the sensor: The simplest and most common cause to check first.
• 2. Cracked or disconnected vacuum hose to the sensor: A very common and inexpensive fix on engines that use a hose fed sensor.
• 3. Failed manifold pressure sensor: The sensor element can fail outright with age or heat exposure.
• 4. Damaged wiring between the sensor and the computer: Chafing near the intake manifold is a common wear point.
• 5. Blown fuse feeding the sensor circuit: Quick to rule out before more involved diagnosis.

What P0105 means for driving the car

The engine typically falls back to a default load estimate and remains drivable, though roughly.

This is a severity 2 of 4 code. It will not usually strand you, but it will fail an emissions test while it is present, and the underlying fault rarely gets cheaper by being left alone.

What does it cost to ignore P0105?

Running on a default load estimate wastes fuel and can cause rough running severe enough to be annoying on a daily basis, though it rarely causes engine damage by itself.

There is also the diagnostic cost of waiting. Freeze frame data, pending code history and the readiness monitor state all describe the fault as it was when it set, and all of it is lost the moment somebody clears the code to make the lamp go out.