OBD-II Code P1105 — What It Means & How to Fix It

What Does This Error Mean?

P1105 means the MAP/BARO (Manifold Absolute Pressure / Barometric Pressure) Sensor has switched to Altitude Mode. Some vehicles use the MAP sensor to also measure barometric pressure at key-on. When the sensor switches to altitude compensation mode unexpectedly or reads outside the normal range, P1105 is set. You may notice rough idle, hesitation, or the engine running rich or lean — especially after changes in altitude.

Affected Models

Vehicles where the MAP sensor doubles as the BARO sensor at key-on
Common in Toyota and Lexus vehicles with combined MAP/BARO sensor logic
Common in Honda and Acura vehicles with altitude sensing in the MAP circuit
Common in some GM vehicles using MAP sensor barometric compensation

Common Causes

Failed MAP sensor not providing an accurate reading for both MAP and BARO functions
Vacuum leak at the MAP sensor port preventing correct manifold pressure reading
Cracked or disconnected vacuum hose to the MAP sensor
Blocked MAP sensor port from carbon buildup in the intake manifold
Wiring issue causing the sensor to read a fixed voltage interpreted as altitude mode

How to Fix It

Inspect the vacuum hose connecting the MAP sensor to the intake manifold. Look for cracks, kinks, or disconnections.

A split vacuum hose is the most common and easiest fix for P1105 — it takes 5 minutes to replace.
Remove the MAP sensor vacuum hose and check the port in the intake manifold for carbon blockage.

Carbon deposits can completely block the MAP sensor port over time on high-mileage engines. Use a thin tool to clear the port.
Use a scan tool to monitor MAP sensor voltage or pressure reading at key-on (before starting). The reading should reflect current barometric pressure.

At sea level, normal MAP/BARO at key-on is approximately 14.7 PSI or 1 bar (100 kPa). At altitude, it reads lower.
Test MAP sensor voltage at idle vs. wide-open throttle. At idle, vacuum is high (low absolute pressure). At WOT, vacuum drops (pressure rises toward atmospheric).

A sensor stuck at a fixed voltage regardless of throttle position is faulty and needs replacement.
Replace the MAP sensor if it fails voltage tests or does not respond to vacuum changes. Clear codes and drive to confirm normal operation.

On Toyota and Honda vehicles, an OEM or Denso/Keihin sensor is recommended for accurate readings.

When to Call a Professional

MAP sensor replacement costs $100 to $300. Vacuum hose repair is $50 to $150. Intake cleaning for a blocked MAP port is $150 to $300. This is generally a moderate, straightforward repair.

Frequently Asked Questions

What is altitude mode on a MAP sensor?

Some PCMs use the MAP sensor reading at engine-off to estimate barometric pressure (altitude). This helps the engine compensate for thinner air at high altitudes. When the sensor reads a value that corresponds to an unexpected altitude, the PCM sets P1105.

Can driving at high altitude trigger P1105?

Normally no — the system is designed to handle a range of altitudes. However, if the sensor is already marginal, large changes in altitude can push the reading outside the accepted range. A healthy sensor handles altitude changes without setting codes.

Will a bad MAP sensor affect fuel economy?

Yes — the MAP sensor is a primary input for fuel injection calculations. An inaccurate MAP reading causes incorrect fueling, which leads to either rich or lean conditions. Both reduce fuel economy and can cause rough running.