MAP/barometric pressure circuit input low

What P0107 means

The MAP sensor is a pressure transducer that generates a voltage proportional to intake manifold pressure. It operates on a 5-volt reference supply from the PCM and a dedicated sensor ground, and outputs a varying signal. At idle (high vacuum) the output is low, roughly 1-2 V; at wide-open throttle (pressure near atmospheric) the output rises to approximately 4.5 V. P0107 is stored when the MAP signal voltage falls below the minimum acceptable threshold while engine speed is 600-3500 RPM and battery voltage exceeds 10 V. It is a one-trip fault that stores immediately; the MIL may also trigger an ETC (electronic throttle control) warning on equipped vehicles. Three consecutive clean trips are required to extinguish the MIL after repair.

Symptoms

• Illuminated check engine light, sometimes with an ETC warning light
• Engine running very rich — PCM defaults to a high-load fuel calculation when MAP is stuck low
• Black smoke from exhaust and elevated fuel consumption
• Sluggish or hesitant throttle response
• Hard start or extended crank when warm

Common causes

• Faulty MAP sensor — internal transducer failed shorted to ground or open
• Signal wire (K1) shorted to ground, pulling the voltage below the minimum threshold
• Open circuit or short to ground on the 5-volt supply wire (K856) to the MAP sensor
• MAP signal circuit shorted to the sensor ground return (K900) — dragging the signal low
• Excessive resistance in the MAP signal circuit between sensor and PCM
• Cracked or disconnected vacuum line to the sensor port causing a different pressure than manifold

Severity & driving advice

Severity: medium — Engine runs very rich, risking catalytic converter damage and high fuel consumption. Driveability is significantly degraded.

Can I drive? Limit driving. Rich mixture risks catalyst damage.

Diagnostic approach

1. Measure 5-volt supply at the MAP sensor connector — Disconnect the MAP sensor. With ignition on (engine off), measure voltage on the 5-volt supply circuit (K856) at the sensor harness connector. The expected voltage is 4.5 to 5.2 V. A reading outside this range points to a supply circuit fault — check for shorts to ground or excessive resistance in the K856 wire back to the PCM.
2. Monitor MAP signal voltage with sensor unplugged — With the MAP sensor disconnected and ignition on, check the scan tool MAP voltage reading. It should read approximately 5.0 V (plus or minus 0.1 V) with the connector removed, as the PCM's internal pull-up holds the signal near the reference. A voltage below 4.5 V with the sensor disconnected confirms the signal circuit is shorted to ground between the connector and the PCM.
3. Check MAP signal circuit resistance to chassis ground — Turn ignition off. Disconnect the MAP sensor and the PCM C2 connector. Measure resistance between the MAP signal pin (K1) at the sensor harness connector and chassis ground. Resistance must exceed 100 ohms. A reading below 100 ohms confirms the signal wire is shorted to ground and must be repaired before installing a new sensor.
4. Check for cross-short between signal and sensor ground circuits — With both the sensor and PCM disconnected, measure resistance between the MAP signal circuit (K1) and the sensor ground circuit (K900) in the sensor harness connector. A reading below 100 ohms means the two wires are shorted together — typically at a chafed point in the harness — and must be separated.
5. Inspect vacuum hose, then replace MAP sensor if circuits are healthy — Check the MAP sensor vacuum port and connecting hose for cracks, kinks or a disconnected fitting. A collapsed hose can produce an erratic low-pressure reading at certain engine speeds. If the vacuum path and all circuit resistances are within specification (above 100 ohms for shorts, below 5 ohms for continuity), replace the MAP sensor and confirm signal voltage varies normally with engine load.

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