POST UPDATED IN February, 2023

Description of DTC code P0400 Generic

The EGR valve (Exhaust Gas Recirculation) is responsible for controlling the exhaust gases through a regulation system of these gases that return to the cylinder. The PCM (Powertrain Control Module) decides the quantity based on conditions such as motor load, temperature and others. If the Power Train Control Module (PCM) determines that the quantity of exhaust gases entering the cylinder is not enough, the diagnostic code P0400 OBD2 is established.

Symptoms of fault code P0400 Generic

  • The service light comes on.
  • The temperature value is high.
  • Nitrogen oxide emissions increase.

Causes of OBD2 P0400 Generic

An establishment of code P0400 can mean that:

  • There may be an element that clogs the Exhaust Gas Recirculation (EGR) valve.
  • Vacuum lines may be defective or even disconnected from the Exhaust Gas Recirculation (EGR) valve.
  • It is possible that some cable of the EGR valve solenoid is in poor condition.
  • The EGR solenoid (Exhaust Gas Recirculation) may be defective.
  • The EGR valve may be defective.

Possible solutions of the DTC code P0400 Generic

To solve the P0400 OBDII diagnostic code, you can do the following:

  • With the help of a scanning tool, it manipulates the Exhaust Gas Recirculation (EGR) valve and with the engine running it verifies its operation. In case of instability, it is indicative that the problem is in the wiring or there is intermittent blocking.
  • If, on the other hand, the motor does not show instability and does not turn off, it is possible that the EGR (Exhaust Gas Recirculation) ports are obstructed; you can remove the EGR valve and clean all the ports.
  • Check the solenoid of the Exhaust Gas Recirculation (EGR) valve.
  • You can check that no solenoid cable of the EGR valve is worn. Repair or change as necessary.


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