P0106 Code: Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance

What the P0106 code means

The manifold absolute pressure (MAP) sensor measures the vacuum the engine creates as it draws air in. With the throttle closed, the pressure inside the manifold falls far below atmospheric. At full load it comes close to atmospheric. From that reading the computer works out how much air is entering and calculates injection.

The P0106 code is not an electrical range code like P0107 or P0108, which flag impossible voltages. It is a plausibility code: the signal is within electrically valid values, but it does not match what the engine should be doing.

The computer has other references to judge it by, such as engine speed, throttle position and, if the engine has one, the air flow sensor. When the MAP drifts away from that calculation for a sustained period, the code is stored.

That narrows the diagnosis to two fronts. Either the sensor reads wrong, because it is dirty or its hose is clogged, or it reads right and the manifold pressure really is abnormal because of a vacuum leak. Separating the two comes first.

A practical tip that speeds up the diagnosis a lot: compare the MAP value with the air flow sensor value if the engine has both. They measure the same thing in different ways, so a mismatch between them identifies which one is reporting wrong without taking anything apart.

And if the engine only has a MAP sensor, the free reference is the atmosphere itself. With the key on and the engine off, the sensor must read exactly the atmospheric pressure where you are. An error there is a sensor calibration error, not a leak.

P0106 code symptoms

• Check engine light on.
• Unstable idle, or an engine that stalls when you come to a stop.
• Hesitation and lack of response when you accelerate.
• Higher fuel use.
• Hard starting.
• Black smoke if the computer enriches the mixture too much.
• Loss of power on hills.
• An audible hiss if there is a major vacuum leak.
• A mismatch between the MAP value and the air flow sensor value on engines that have both.
• A wrong reading with the key on and the engine off.

Likely causes of the P0106 code

1. Vacuum leaks in hoses, the manifold gasket, the PCV valve or the brake booster. The most frequent cause.
2. MAP sensor hose cracked, loose or clogged on remote-mounted sensors.
3. Sensor dirty with carbon or oil at its pressure port.
4. Failed or out-of-calibration MAP sensor.
5. Connector with corroded pins or moisture.
6. Exhaust leak or clogged catalytic converter, which changes the real filling of the engine.
7. Timing off by a tooth or more, which changes the vacuum the engine generates.
8. Low compression in one or more cylinders.
9. EGR valve that does not close.
10. Sensor out of calibration from the factory on lower-quality replacements.
11. Manifold pressure port clogged with carbon on high-mileage engines.

How to diagnose the P0106 code step by step

1. Watch the MAP value with the key on and the engine off. It should read atmospheric pressure, around 101 kilopascals (14.7 psi) at sea level and less at altitude.
2. Check the value at warm idle. A healthy engine reads between 25 and 40 kilopascals (about 7 to 12 inHg). A higher value points to a vacuum leak or a filling problem.
3. Rev the engine and let off, watching the response. It should rise with load and drop sharply when you let go.
4. Inspect the sensor hose if it is mounted remotely. Cracks, kinks and clogs are common.
5. Smoke test the intake to locate vacuum leaks.
6. Clean the sensor pressure port if there is carbon or built-up oil.
7. Check power, ground and signal at the connector.
8. Measure exhaust backpressure if there is a loss of power, to rule out a clogged catalytic converter.
9. Compare the MAP with the air flow sensor if the engine has both. The mismatch identifies which one is reporting wrong.
10. Compare the key-on, engine-off reading with the atmospheric pressure where you are. An error there points to an out-of-calibration sensor.

How to fix the P0106 code

• Repair the vacuum leaks you find and replace the PCV valve if it is stuck.
• Replace the sensor hose if it is cracked, crushed or clogged.
• Clean the sensor pressure port with a cleaner made for it, without getting liquid into the sensing element.
• Replace the MAP sensor if, with a sealed intake and a clean hose, it still reports values that do not make sense.
• Clean or replace the corroded connector.
• Replace the intake manifold gasket when the smoke test confirms it.
• Deal with the clogged catalytic converter or the off timing if the real filling is abnormal.
• Clean the manifold pressure port if it is clogged with carbon, not just the sensor.
• Use parts from a recognized manufacturer, because cheap ones often come out of calibration from the factory.

Technical reference data

• Pressure with the key on and the engine off: atmospheric, about 101 kPa (14.7 psi) at sea level.
• Pressure at warm idle: between 25 and 40 kPa on a healthy engine.
• Pressure at full load on a naturally aspirated engine: close to atmospheric.
• Typical sensor signal: 0.5 to 4.5 volts, or a frequency signal depending on the type.
• Altitude lowers atmospheric pressure: at 2,200 meters (about 7,200 feet) it is around 78 kPa (11.3 psi), something to keep in mind in high-altitude cities.
• 5 volt supply with its own ground.
• With the key on and the engine off, the MAP must read the exact atmospheric pressure of the location.
• A sustained mismatch between the MAP and the air flow sensor identifies which of the two is reporting wrong.

Brand-specific notes

In high-altitude cities the atmospheric pressure is noticeably lower and the reference values change. With a P0106 code, a MAP that reads 78 kilopascals with the engine off is not bad if you are at 2,200 meters (about 7,200 feet). It is measuring correctly.

On sensors mounted away from the manifold, the hose is as suspect as the sensor itself. Check all of it before you buy anything, paying attention to kinks and hardened ends.

Frequently asked questions about P0106