A rough idle, poor fuel economy and a check engine light can all come from one small sensor on the intake manifold. The manifold absolute pressure (MAP) sensor tells the engine how hard it is working. A P0105 code means the engine computer found a problem in that sensor’s circuit.
This guide explains what the sensor does, why the circuit fails and how to test it with a multimeter. You will also see which repairs fix the problem most often.
P0105 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 1 | Fuel and air metering | The fault involves the sensors that measure air and fuel. |
| 05 | Specific fault | Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction |
What the MAP Sensor Does
The MAP sensor measures air pressure inside the intake manifold. At idle, the engine pulls a strong vacuum, so pressure is low. At full throttle, pressure rises close to outside air pressure. On turbocharged engines, it climbs above outside pressure under boost.
The powertrain control module (PCM) uses the reading to judge engine load. Load affects fuel delivery, ignition timing and transmission shifts. Some engines, called speed density designs, have no mass air flow sensor and rely on the MAP sensor for all airflow math.
Many PCMs also use the MAP sensor as a barometric (BARO) sensor. With the key on and the engine off, manifold pressure equals outside air pressure. Other vehicles use a separate BARO sensor or one built into the PCM.
What the P0105 Code Means on Your Vehicle
The SAE J2012 standard defines the P0105 code as Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction. It is a general circuit fault. The PCM found a problem with the sensor’s voltage, reference or ground, but the exact symptom does not fit a high or low code.
Most MAP sensors use three wires:
- 5-volt reference from the PCM
- Ground, also called the low reference
- Signal back to the PCM, which changes with pressure
On many GM vehicles, the signal reads about 4.5 volts with the key on and the engine off at sea level. It drops to roughly 1 to 1.5 volts at a warm idle. Your service manual lists the exact values for your engine.
Signs of a MAP Circuit Problem
A bad load reading throws off fuel and timing. Symptoms of a P0105 code depend on whether your engine also has a MAF sensor. Speed density engines tend to run much worse. Watch for these signs:
- Check engine light on
- Rough idle or stalling
- Hesitation or poor power on acceleration
- Black smoke or a fuel smell from a rich mixture
- Poor fuel economy
- Hard starting
- Harsh or late transmission shifts on some vehicles
Common Causes of the P0105 Code
The circuit is simple, so the list of causes is short. Wiring and connector faults top the list. These are the usual causes:
- Loose or corroded connector. The sensor sits on a hot manifold, and heat cycles wear connectors out.
- Damaged wiring. Wires can chafe, melt or break near the manifold.
- Shorted 5-volt reference. Many PCMs share one reference circuit with other sensors, such as the throttle position sensor. A short in any of them can drag the reference down.
- Failed MAP sensor. The internal pressure element can fail with age.
- Damaged or clogged vacuum hose. On remote-mounted sensors, a split or blocked hose gives a false reading.
- PCM fault. On vehicles with the BARO sensor inside the PCM, an internal fault can set the P0105 code. This is rare.
How to Test the MAP Sensor Circuit
You need a digital multimeter, a scan tool with live data and a wiring diagram. A hand vacuum pump helps you test the sensor itself.
Compare MAP and BARO Readings
Turn the key on without starting the engine. Look at the MAP and BARO readings on the scan tool. Both should read close to local air pressure, which is about 101 kPa or 29.92 inches of mercury (inHg) at sea level. That is the standard sea-level pressure the U.S. National Weather Service uses.
The readings drop as altitude rises, so expect lower numbers in mountain areas. If the MAP reading sits far from BARO, or reads 0 or a fixed maximum, the circuit has a fault. Start the engine next and confirm that MAP drops at idle.
Test the Three Wires
Back-probe the connector with the sensor plugged in and the key on:
- Reference wire: Should read close to 5 volts. A low or zero reading points to a shorted sensor on the shared reference, an open wire or a PCM fault.
- Ground wire: Should read close to 0 volts against the battery negative post.
- Signal wire: Should match the scan tool reading and change as the engine runs.
If the reference reads low, unplug other sensors on the same circuit one at a time. The reference returns to 5 volts when you unplug the shorted one.
Test the Sensor with a Vacuum Pump
Remove the sensor or its hose and connect a hand vacuum pump. Watch the signal voltage while you apply vacuum. The voltage should drop smoothly as vacuum rises and return when you release it. A sensor that jumps, sticks or does not move has failed.
How to Fix the P0105 Code
Fix what your tests showed, then clear the code and road test the vehicle. The most common repairs are:
- Clean or replace the connector if pins are loose or corroded.
- Repair damaged wiring with solder and heat shrink tubing, then secure it away from heat.
- Fix a shorted reference by repairing the wire or replacing the sensor that drags it down.
- Replace the vacuum hose on remote-mounted sensors if it is cracked or blocked.
- Replace the MAP sensor if the circuit tests good but the sensor fails the vacuum test.
Repair Cost Overview
MAP sensors are usually cheaper than MAF sensors. This table lists typical ranges.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Vacuum hose | $5 to $20 | $50 to $100 |
| Connector pigtail | $15 to $40 | $100 to $200 |
| Wiring repair | $10 to $30 | $100 to $300 |
| MAP sensor replacement | $30 to $150 | $100 to $300 |
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0102 | Mass or Volume Air Flow “A” Circuit Low |
| P0103 | Mass or Volume Air Flow “A” Circuit High |
| P0104 | Mass or Volume Air Flow “A” Circuit Intermittent/Erratic |
| P0106 | Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance |
| P0107 | Manifold Absolute Pressure/Barometric Pressure Circuit Low |
Getting the Manifold Pressure Circuit Working Again
A P0105 code means the PCM cannot trust the pressure signal. Wiring, connectors and a shared 5-volt reference cause most cases.
- Compare MAP and BARO with the key on and the engine off.
- Test the reference, ground and signal wires.
- Check the sensor with a vacuum pump.
- Replace the sensor only after the circuit tests good.
Frequently Asked Questions
Where Is the MAP Sensor Located?
Most MAP sensors mount directly on the intake manifold or the throttle body. Some older vehicles mount the sensor on the firewall or inner fender with a vacuum hose running to the manifold. Turbocharged engines often have one sensor near the throttle and another boost sensor in the intake tube.
Can I Drive with a P0105 Code?
Most vehicles still run, but performance and fuel economy suffer. On engines without a MAF sensor, the PCM may run on a fixed backup value, which can cause stalling. A rich mixture can also damage the catalytic converter. Plan the repair soon and avoid long trips until then.
Do I Need to Relearn Anything After Replacing the Sensor?
Most vehicles do not need a special relearn after a MAP sensor replacement. Clear the codes with a scan tool, then drive normally so the PCM can adjust its fuel trims. A few makes recommend an idle relearn, so check your service manual for any extra steps.
Can Other Sensors Set the P0105 Code?
A shorted sensor that shares the 5-volt reference can pull the circuit down and set MAP codes. Throttle position, fuel tank pressure and air conditioning pressure sensors often share that reference. If several sensor codes appear at once, suspect the shared reference before you replace parts.