DTC P0400

DTC: P0400 Exhaust gas recirculation flow malfunction (functional response)

Activation requirement CHECK ENGINE lamp:
After one "performed" test with failure

Activation of CHECK ENGINE lamp:
At start of next trip.

Test to detect fault:
The EGR logic chain is checked if the following conditions are simultaneously satisfied:
^ No failure in the electrical activation of the EGR switchover valve (Y27)
^ Deceleration fuel shut-off operating
^ Closed throttle position recognized
^ Engine speed approximately 1900-2600 rpm and constant
^ Intake manifold pressure less than 325 mbar
^ Momentary intake air temperature >10 °C.

After approximately 1 second, the diagnostic module determines the intake manifold pressure. Initiated by the diagnostic module (via the CAN data bus), the engine control module then briefly activates the EGR switchover valve. The intake manifold pressure is evaluated for approximately 3 seconds.

The pressure in the intake manifold must drop by at least approximately 15 mbar while the EGR switchover valve is activated.