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DTC codes / Mitsubishi codes / P1400

P1400 · MitsubishiManifold Differential Pressure Sensor Circuit

P1400 on Mitsubishi vehicles indicates that the powertrain control module has detected a fault in the manifold differential pressure sensor circuit, which measures the pressure difference between the intake manifold and atmospheric pressure. The computer monitors the sensor's signal voltage and sets this code when the reading falls outside the expected range or is inconsistent with other engine operating parameters.

SystemPowertrain
Code typeMitsubishi specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Rough idle or unstable engine speed, especially when cold
  • Poor fuel economy or reduced engine performance
  • Hesitation or stumble during acceleration
  • In rare cases, the engine may enter limp mode or stall

Common causes, most likely first

  1. Faulty manifold differential pressure sensor
  2. Damaged or disconnected sensor wiring or connector
  3. Clogged or cracked vacuum hose connected to the sensor
  4. Leaking or restricted intake manifold passages
  5. Corroded or damaged electrical terminals at the sensor or PCM
  6. PCM internal fault (rare)

How to diagnose and fix it

  1. Inspect the sensor and its wiring for obvious damage, corrosion, or loose connections
  2. Check the vacuum hose for cracks, clogs, or disconnection and replace if necessary
  3. Measure the sensor's reference voltage and signal voltage with a multimeter and compare to specifications
  4. Test the sensor's output with a vacuum pump to verify it responds correctly to pressure changes
  5. Check for intake manifold leaks or restrictions that could affect the pressure differential
  6. If the sensor fails testing, replace it and clear the code
  7. If the wiring and sensor are good, diagnose the PCM and its connections

Common Misdiagnosis of P1400

  • A clogged or cracked vacuum hose is frequently the real culprit, yet many technicians replace the sensor without checking the hose first.
  • The manifold differential pressure sensor on Mitsubishi engines often shares a circuit with the EGR system, so a fault in the EGR valve or its passages can trigger P1400.
  • A dirty or failing mass airflow sensor can cause pressure readings to go out of range, leading to a false P1400 without any issue in the differential pressure sensor circuit itself.
  • On some models, the sensor is mounted in a location exposed to heat and vibration, leading to internal failures that don't show up in static resistance tests.
  • After replacing the sensor, a relearn or adaptation procedure may be required on certain Mitsubishi models to prevent the code from returning.

Can I keep driving with P1400?

You can generally drive the vehicle with this code, but expect reduced fuel economy and possible driveability issues; avoid heavy acceleration or towing until the fault is repaired.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Mitsubishi vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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