P0401

Read the instructions below then start the fault diagnostic procedure.

Symptom: None.

P0401

Fault symptom

•

None.

On-Board Diagnostics

Type of diagnosis:

-	Continuous.

Enable criteria:

-	Battery voltage: 10.2-15.8 V.

-	P1636 or P1637 must not be detected.

-	The difference in engine speed from two measurements must not exceed 40 rpm.

-	The difference between two injections must not exceed 1.5 mm 3 /C.

-	Gear lever in neutral.

-	Requested EGR flow: 26-65 %.

-	Speed: 0-10 km/h.

-	Injection quantity: 3-9 mm 3 /C.

-	Intake air temperature: 20-95 °C.

-	Atmospheric pressure: 90-110 kPa.

-	These conditions must be fulfilled for 3 seconds before diagnostics run.

Fault criteria:

-	EGR flow: 21 % lower than desired for 33 sec.

Dependents:

-	P0101, P0102, 0103, P0112, P0113, P01403, P1404.

System reaction to a fault:

-	EGR is switched off.

OK report:

-	Fault criteria not fulfilled.

Fault handling: (See section Fault handling III, other emissions-related components and functions for more information)

-

Type III.

Diagnostic help

Read value: Target EGR Ratio, EGR Ratio

The EGR function is switched off after 1 minute of idling (EGR valve closed). As soon as the accelerator pedal is touched, EGR control is reactivated.

See also the description of read values under Menu "Read values" for more information.

Checking the wiring harness

Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short circuits. Observe the multimeter, diagnostic tool or test lamp during the check.