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P0106: MAP sensor range/performance and the vacuum leaks behind it
P0106 compares manifold pressure against what the ECU expects from throttle position and RPM. Most of the time the sensor is honest and the intake is leaking.
P0106 “Manifold Absolute Pressure Sensor Range/Performance” is the pressure-side twin of P0101. The ECU knows roughly what manifold pressure should be for a given throttle angle and engine speed. When the sensor disagrees for long enough, this code appears.
Understanding the number before you diagnose it
MAP is reported in absolute pressure, not vacuum. That trips people up constantly.
| State | Typical MAP (naturally aspirated) |
|---|---|
| Key on, engine off | equals barometric pressure, roughly 101 kPa at sea level |
| Warm idle | 25–40 kPa |
| Snap throttle | brief spike towards 90–100 kPa |
| Wide open throttle | 95–101 kPa |
| Overrun, throttle closed | 15–25 kPa |
The key-on-engine-off reading is the free calibration check. It must match ambient barometric pressure. If the engine is off and MAP reads 80 kPa while you are at sea level, the sensor is drifting and nothing else you measure will be trustworthy.
On a turbocharged engine the ceiling moves: boost pushes MAP well above 101 kPa, often to 180–250 kPa. Related reading: turbo diagnostics for underboost and overboost.
Why the sensor is usually innocent
An idle MAP of 50 kPa on an engine that should idle at 30 kPa means the manifold is not holding vacuum. The sensor is reporting that faithfully. Common causes:
Vacuum leaks
Cracked intake boots, perished vacuum hoses, a failed brake booster diaphragm, a leaking intake manifold gasket. Idle rises, idle control fights back, fuel trims go positive. When P0106 arrives alongside P0171, a leak is the first suspect.
A stuck-open EGR valve
Exhaust gas dumped into the manifold at idle raises pressure and roughens the idle. See P0404 and EGR position for how to confirm valve position against commanded position.
PCV system faults
A stuck-open PCV valve is a calibrated vacuum leak that the engine was never meant to have. Very common on high-mileage engines.
Blocked vacuum port or hose to the sensor
Where the sensor mounts remotely and connects by hose, that hose can fill with oil or carbon. The sensor then reads a damped, delayed version of reality and fails the plausibility test.
Genuine sensor failure
Silicon diaphragm sensors drift with age and heat. Symptoms are a wrong key-on-engine-off reading, or a value that sticks during throttle changes.
Camshaft timing: the cause nobody checks
A stretched timing chain that has retarded cam timing by a few degrees lowers idle vacuum measurably. If MAP at idle is high, the intake holds vacuum under a smoke test, and the engine has a rattle on cold start, look at timing before buying sensors. Background: timing chain vs belt DTC codes.
The same applies to badly carboned intake valves on direct-injection engines — see GDI carbon buildup.
A diagnostic sequence that works
- Key on, engine off. Compare MAP against local barometric pressure. Fail here and the sensor is condemned without further work.
- Warm idle. Log MAP for 60 seconds. Steady and in the 25–40 kPa band is healthy. High and wandering points at a leak.
- Snap throttle test. MAP should spike towards atmospheric and drop back sharply. A lazy, rounded response suggests a blocked hose or a slow sensor.
- Overrun test. Lift off at 3000 rpm in gear. MAP should dive below idle value. If it does not, the throttle plate is not sealing or the exhaust is restricted.
- Smoke test the intake. Cheap, fast, conclusive for leaks.
Cost expectations
- Vacuum hose or intake boot: $10–80.
- PCV valve: $15–60.
- Intake manifold gasket: $40–120 in parts, labour varies hugely by engine.
- MAP sensor: $25–120.
Confirming the fix
After the repair, watch idle MAP settle into range and fuel trims return towards zero. Then let the readiness monitors run — OBD readiness monitors explained covers what “complete” actually requires.
Try it on the free tier of the app — pair an ELM327 adapter and log MAP, RPM and Throttle Position together. The key-on-engine-off barometric check alone takes ten seconds and settles the sensor question before you spend anything.
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