P0106
- Powertrain
- Generic (SAE)
- Emissions
Diagnose soon
Load calculation is wrong, so fueling and spark timing are wrong, but the engine keeps running on backup strategies. It matters more when the underlying cause is an intake leak or an exhaust restriction, since both cause problems of their own beyond this code.
- Safe to drive
- Usually drivable short term. Stop driving if it stalls, surges, or loses noticeable power — and stop immediately if the brake pedal becomes hard or takes much more effort than usual, which means the leak has reached the brake booster and power assist is failing.
Manifold Absolute Pressure Sensor Range/Performance
The manifold pressure sensor's reading does not agree with what the computer expects from engine speed and throttle position. Either the sensor is lying, or the engine genuinely is not producing the vacuum it should.
The MAP sensor measures absolute pressure inside the intake manifold, which the ECM uses to calculate engine load and, from that, fueling and spark timing. The ECM holds a model of expected manifold pressure for any given throttle angle and rpm, and cross-checks the sensor against it — plus, at key on with the engine off, against barometric pressure. P0106 sets when the reading sits within its electrical limits but is implausible, which separates it from P0107 and P0108, the voltage limit codes on the same circuit.
How the car detected itTwo checks matter. With the key on and the engine not running, manifold pressure equals atmospheric pressure, so the sensor should report the local barometric value — roughly 101 kPa, or about 29.9 inches of mercury, at sea level and proportionally less at altitude. With the engine running, the ECM verifies that pressure falls on closed-throttle deceleration and rises with throttle opening in the expected proportion. Failing either check for a calibrated time sets the code. Some vehicles also compare MAP against a mass airflow sensor where both are fitted.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually drivable short term. Stop driving if it stalls, surges, or loses noticeable power — and stop immediately if the brake pedal becomes hard or takes much more effort than usual, which means the leak has reached the brake booster and power assist is failing.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- If ignored
- Expect poor fuel economy, hesitation, hard starting, rough idle and a failed emissions test. If the cause is a vacuum leak on a manifold that also feeds the brake booster, brake assist can weaken — which is a safety concern, not just a driveability one.
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
These are the causes this code can have. For the order to work through them in, see what to check first.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Vacuum hose to MAP sensor cracked or detached | Very common | — |
| 2 | MAP sensor drifting outside specification | Common | — |
| 3 | Intake manifold gasket leaking | Common | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
In order. Each of these is cheaper or faster than what follows it, and each one can make the rest unnecessary.
The vacuum hose or manifold port serving the sensor
Cracked, oil-softened, kinked or carbon-plugged is the most common and cheapest cause. On sensors mounted directly to the manifold, check the port itself for carbon.
The reading with the key on and the engine off, against the local barometric value
With the engine stopped it must equal atmospheric pressure. If it does not, the sensor has drifted or the circuit is faulty, and you have that answer before the engine even starts.
Idle vacuum on a mechanical gauge
This is the one test that separates a lying sensor from an engine that genuinely is not breathing. A mechanical gauge does not care what the ECM believes.
Companion codes for lean running, misfire, or throttle position
Codes rarely arrive alone. A lean bank code alongside this one steers you straight to an intake leak instead of the sensor.
The sensor connector and pigtail
Corroded terminals and chafed wiring produce erratic readings that look exactly like a drifting sensor and cost far less to fix.
Capture freeze frame and the full code set
Tools Scan tool with freeze frame access
Note rpm, throttle angle, load and reported manifold pressure at the moment of failure, and whether other sensors faulted at the same time.
ExpectedA specific operating condition to reproduce, and a code pattern that points toward sensor, wiring, or engine breathing.
Compare the reading to barometric pressure, key on and engine off
Tools Scan tool
With the engine stopped, manifold pressure and atmospheric pressure are the same thing. Adjust your expectation for local altitude.
ExpectedA value within a couple of kPa of the local barometric reading — near 101 kPa at sea level, proportionally lower with altitude.
Inspect the vacuum hose and the manifold port
Tools Basic hand tools, soft pick or nylon brush, carbon solvent
Remove the hose and clear the port. Direct-injection and turbocharged engines commonly carbon the port until the sensor responds slowly rather than not at all, which is exactly what a range and performance code catches. Clear the port with solvent and a soft pick or brush. Do not drill or ream it — some ports carry a calibrated restriction, and enlarging it changes how the sensor responds.
ExpectedA clear, unrestricted passage and a supple, correctly seated hose with no splits at the ends.
Apply vacuum with a hand pump and watch the signal track
Tools Hand vacuum pump, scan tool
Pull vacuum in steps and hold at each one, watching the reported value follow.
ExpectedThe reading falls smoothly and proportionally with applied vacuum, holds steady at each step, and returns cleanly. Steps, sticking or lag condemn the sensor.
Compare scan data against a mechanical vacuum gauge
Tools Mechanical vacuum gauge, scan tool
Connect a gauge to a manifold vacuum source and compare it against scan data at idle and at raised rpm. This test decides whether the sensor is wrong or the engine is.
ExpectedSteady vacuum in the high teens to low twenties inches of mercury at warm idle at sea level, with the scan value agreeing. A low, fluctuating, or slowly falling gauge points at the engine — intake leak, exhaust restriction, cam timing, or valve sealing — but it does not identify which of those, so treat it as a signal to test further rather than as a diagnosis.
Smoke test the intake manifold and all vacuum accessories
Tools Smoke machine
Seal the intake and introduce smoke, checking every gasket and every vacuum-consuming device. Pay particular attention to the brake booster and its hose — a leak there weakens power braking as well as setting this code.
ExpectedNo smoke from the manifold gaskets, throttle body gasket, brake booster or its hose, PCV system, or purge lines.
Test the sensor circuits with a wiggle test
Tools Digital multimeter, back-probe leads, wiring diagram
Back-probe the 5 volt reference, low reference and signal wires at the connector while flexing the harness.
ExpectedReference near 5 volts, ground under about 0.1 volt of drop, and a stable signal that does not glitch during flexing.
Repair the indicted fault and prove it with a drive cycle
Tools Scan tool
Clear the code and drive the vehicle through the conditions in the freeze frame so the monitor can rerun.
ExpectedNo pending or confirmed codes and the relevant monitors reporting complete.
| Repair | Only after you confirm | Typical cost | Who |
|---|---|---|---|
| Replace the sensor vacuum hose or clear the manifold port | The hose is found cracked or collapsed, or the port carbon-restricted, with readings normalizing once cleared | $30–$180 | DIY |
| Replace the manifold absolute pressure sensor | The sensor fails to track applied vacuum smoothly, or misreads barometric pressure at key on, with reference, ground and signal circuits all good | $90–$320 | DIY |
| Repair intake manifold gasket or vacuum leaks | Smoke testing locates the leak and manifold vacuum returns to a normal range once it is sealed | $150–$900 | Hard |
| Repair or replace the sensor connector or wiring | Reference or ground voltage out of range, or signal glitches reproduced during a wiggle test | $100–$350 | DIY |
| Replace a restricted catalytic converter or exhaust section | Measured exhaust backpressure above the manufacturer's limit, taken at the upstream oxygen sensor bung or a test port | $500–$2,500 | Shop |
| Correct cam timing or repair a stretched timing chain and tensioner | Camshaft position measured retarded relative to specification, or timing marks found out of alignment on inspection, with intake leaks and exhaust restriction already ruled out by smoke test and backpressure measurement. A low vacuum reading on its own is not sufficient — it only tells you to look further | $700–$3,000 | Shop |
Most of these end cheaply — a hose, a cleared port, or a sensor. The expensive outcomes are exhaust restriction and timing, and a mechanical vacuum gauge test that takes minutes tells you whether to look that far. It does not tell you which of the two, so insist on measured backpressure or measured cam position before authorizing either job.
- Replacing the sensor without clearing carbon from its port — the new one restricts the same way.
- Drilling or reaming the manifold port to clear it, which can enlarge a calibrated restriction and create a new response complaint.
- Trusting scan data over a mechanical vacuum gauge when the two disagree. The gauge wins.
- Missing a leaking brake booster or booster hose, which mimics a manifold gasket leak exactly — and weakens braking.
- Ignoring an exhaust restriction. A plugged catalyst raises manifold pressure at higher rpm and looks convincingly like a sensor fault.
- Forgetting that turbocharged and supercharged engines normally read above atmospheric pressure under boost, so a high number is not automatically wrong.
- Not checking whether the vehicle also carries a mass airflow sensor, since a fault in one can set a correlation code against the other.
- MAP Sensor
- Vacuum Hose
- Intake Manifold
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Reviewed
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