P0400

Exhaust Gas Recirculation Flow Malfunction

DTC P0400, sometimes indicated as P040000 is an OBD diagnostic trouble code indicating a generic fault with the vehicle powertrain (i.e. engine and gearbox). This code identifies an error with the auxiliary emissions system causing exhaust gas recirculation flow malfunction.

The exhaust gas recirculation (EGR) system is designed to reduce emissions by recirculating a portion of the exhaust gas back into the engine. The P0400 code indicates a malfunction in the EGR system.
There are several possible causes for this code, including a defective EGR valve, a leak in the EGR system, or a problem with the EGR solenoid.
If the code is caused by a defective EGR valve, the valve will need to be replaced. If the code is caused by a leak in the EGR system, the leak will need to be repaired. If the code is caused by a problem with the EGR solenoid, the solenoid will need to be replaced.

  • P0400: Exhaust Gas Recirculation Flow Malfunction
  • P0400: Exhaust Gas Recirculation "A" Flow
  • P0400: EGR Flow Malfunction
  • P0400: Exhaust gas recirculation (EGR) system – flow malfunction
  • P0400 00: Incorrect EGR valve signal
  • P0400 00: Exhaust gas recirculation (EGR) system - flow malfunction

DTC Trouble Code Search
Bulletins

Bulletins are notices put out by manufacturers in conjunction with the NHTSA to notify the public of manufacturing issues or changes.

  • TSB-23-13-004 - ENGINE AND ENGINE COOLING
    MITSUBISHI: This technical service bulletin provides instructions to reprogram the ecu with the countermeasure software when the check engine light illuminates with dtc of P0401/ P0400.
  • 11-200-20R - ELECTRICAL SYSTEM:SOFTWARE
    SUBARU: This bulletin announces the availability of reprogramming files to optimize the engine control module (ecm) for hard starting in sub-freezing temperatures, dtc P0400, and surging in high altitudes.
  • 11-197-20 - ELECTRICAL SYSTEM
    SUBARU: This bulletin announces availability of reprogramming files to optimize the engine control module (ecm). These new files address concerns of the check engine light coming on and setting a dtc P0400: egr ⿿a⿝ flow. The dtc can set if the
  • 101215 - ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:GAS RECIRCULATION VALVE (EGR VALVE)
    SUZUKI: Service manual update: egr dtcs P0400, P0401 and P0402. *tt
  • 05040 - ENGINE AND ENGINE COOLING
    NISSAN: Mil with dtc P0400, P0402, rough idle, drivability incidents, difficulty setting egr srt. *sc
  • 05040A - ENGINE AND ENGINE COOLING
    NISSAN: 1998-2000 frontier & xterra with ka24 engine; mil with dtc P0400, P0402, rough idle, drivability incidents, difficulty passing i/m test for no x update *sc
  • 040604075 - ENGINE AND ENGINE COOLING:ENGINE
    CHEVROLET: Check engine light illuminated, diagnostic trouble code (dtc) P0400 set. *tt
  • 84 - ELECTRICAL SYSTEM:IGNITION:MODULE
    MITSUBISHI: Vehicle technical information regarding diagnostic trouble code P0400 egr flow malfunction. *tt
  • 85 - ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:GAS RECIRCULATION VALVE (EGR VALVE)
    MITSUBISHI: Subject regarding diagnostic trouble code P0400 egr flow malfunction. *tt
  • 14742 - UNKNOWN OR OTHER
    MERCURY: Some vehicles may exhibit a malfunction indicator lamp (mil) on with egr system related diagnostic trouble codes P0400, P0401, P0402, P1400, P1401, P1405, P1406, P1408, P1409. *tt
  • 00096 - ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:GAS RECIRCULATION VALVE (EGR VALVE)
    CHEVROLET: Some customers may experience a failure of the exhaust gas recirculation (egr) valve due to corrosion of the internal diaphragm plate, leading to driveability complaints of a check engine light for egr valve (dtc P0400); or engine stall at
  • 99103 - ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:GAS RECIRCULATION VALVE (EGR VALVE)
    MERCURY: On some vehicles the check engine warning lamp may illuminate and diagnostic trouble codes 32, 35, P0400, P0402, P1400, P1401, P1402 or malfunction indicator lamp 0302, 0305, 0306, 0514, 1005 may be stored indicating a malfunction in the ex
  • NTB97100 - VEHICLE SPEED CONTROL:CRUISE CONTROL
    NISSAN: Concerns with truck exhibiting a rough / no idle and / or dtc P0400 stored in the ecm due to egr valve sticking. *tt
  • 97083001897 - ENGINE AND ENGINE COOLING:ENGINE
    MAZDA: Under certain load and rpm ranges excessive noise may be in generated in the egr boost sensor circuit causing dtc P0400 to be set. *yc
  • 776509 - ELECTRICAL SYSTEM:IGNITION:MODULE
    CADILLAC: Dtc P0400 set (install flash calibration). *tw
  • 96258 - ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:GAS RECIRCULATION VALVE (EGR VALVE)
    FORD: Malfunction indicator lamp (mil) - mil lamp illuminated with daignostic trouble code (dtc) P0400 stored in memory. *tw
  • BC9677961001 - VEHICLE SPEED CONTROL:LINKAGES
    MERCURY: Engineering is investigating a concern where the malfunction indicator lamp (mil) is illuminated & code P0400 or P1195 is stored in memory. *tt
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