Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance

What P0106 means

The MAP sensor measures vacuum or pressure inside the intake manifold and converts it to a voltage that the ECM uses to calculate engine load and air mass. At idle, manifold pressure is low (high vacuum) and sensor voltage is low; under full load, pressure approaches atmospheric and voltage rises toward 4.5-4.8 V on most 5 V reference systems. P0106 is a rationality (performance) fault -- the sensor's signal is within its operational voltage range and not stuck at an absolute minimum or maximum, but it disagrees with the other operating parameters (such as MAF readings, throttle position, and RPM) by more than a calibrated threshold. The Ford factory description notes this sets when the MAP PID does not correlate with the BARO or TIP_PRS_BOOST PIDs at ignition on, or when MAP and throttle intake pressure fail to correlate at idle. Common triggers include a slow-responding sensor, a vacuum leak that alters the expected manifold pressure pattern, or a blocked sensor vacuum port.

Symptoms

• Check engine light illuminated
• Rough or hunting idle -- ECM calculates incorrect air mass, producing unstable fuel delivery
• Hesitation or surging on acceleration, particularly at partial throttle
• Stalling, especially at idle when transitioning from closed to open throttle
• Poor fuel economy due to incorrect load calculation
• Possibly dark or sooty exhaust if the ECM commands excessive fuel based on a falsely high MAP reading

Common causes

• Cracked, loose, or disconnected vacuum line between the intake manifold port and the MAP sensor -- most common cause
• MAP sensor contaminated or slow-responding (oil vapour from PCV build-up coating the sensor diaphragm)
• Clogged MAP sensor vacuum port or hose (carbon or oil deposits blocking the pressure signal path)
• Large vacuum leak elsewhere on the intake -- manifold vacuum at the MAP port is affected but the leak is further upstream
• Failed MAP sensor: signal stays within spec range but output does not respond proportionally to actual pressure changes
• Faulty or corroded MAP sensor connector causing intermittent contact and signal drop-outs

Severity & driving advice

Severity: Moderate — Fuel delivery errors from a bad MAP signal can cause misfires, stalling, and catalytic converter damage if rich-running continues long-term.

Can I drive? Driveable with caution. Repair within 1-2 weeks.

Diagnostic approach

1. Inspect the MAP sensor vacuum hose and port — Trace the small vacuum hose from the intake manifold port to the MAP sensor. Look for cracks, kinks, slipped ends, or hardened rubber. Disconnect the hose at the sensor end and apply 20 in-Hg of vacuum with a hand pump -- the scan tool reading should change immediately as vacuum increases. A sensor that does not respond is faulty or its port is blocked with oil deposits.
2. Compare MAP sensor reading against known values on a scan tool — With the engine off, the MAP should read near atmospheric -- approximately 29-30 in-Hg absolute (100 kPa). At warm idle it should drop to 15-22 in-Hg absolute (typical idle vacuum of 15-20 in-Hg gauge). A snap-throttle to wide-open should briefly spike the reading toward atmospheric. A sensor stuck at one value through these conditions is mechanically damaged or its vacuum port is blocked. VREF supply to the MAP sensor should measure 4.0-6.0 V.
3. Check for vacuum leaks with a smoke machine — A large vacuum leak elevates manifold pressure above the expected idle value, pushing the MAP reading outside the normal range for a given RPM. A smoke machine EVAP test or careful propane-enrichment method reveals unintended air entry points around intake gaskets, PCV hoses, throttle body gaskets, and brake booster lines.
4. Measure MAP sensor supply voltage and ground — Backprobe the MAP sensor connector with the engine running. The reference supply pin should read 4.0-6.0 V (Ford spec). The ground pin should read below 0.1 V to body ground. A low reference voltage points to a fault in the 5 V reference circuit shared with other sensors; inspect the reference wire for partial shorts before replacing the sensor.
5. Replace the MAP sensor if all external checks pass — If the vacuum hose and connections are intact, there are no vacuum leaks, and reference voltage is within spec, the sensor diaphragm or sensing element has failed internally. Replace the sensor, clear the code, and retest with a full drive cycle including idle, steady cruise, and wide-open throttle to confirm the rationality monitor passes.

Make & model notes

Ford: On Ford F-150 with the 5.0L V8, P0106 routes to Pinpoint Test DM (Manifold Absolute Pressure Sensor). The 3.5L EcoBoost uses a combined MAP/IAT2 intake pressure and temperature sensor (TMAP) that also covers boost pressure; on that engine P0106 routes to Pinpoint Test EA (Pressure and Temperature Sensor Correlation). Verify which sensor type your engine uses before ordering a replacement.

GM (Chevrolet, GMC, Buick): The 3.8L (L36/L67) and 3.1L/3.4L V6 engines in older GM vehicles are prone to P0106 from a MAP sensor hose that cracks or slips off at high mileage. The sensor on these engines is mounted to the intake plenum and the hose deteriorates from heat cycles. Replacement is inexpensive and frequently resolves the code.

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