PACCAR MX (2004 Emissions) Fault Code: P1400 EGR Mass Flow – Estimated EGR Rate Too High

PACCAR MX (2004 Emissions) Fault Code: P1400 EGR Mass Flow – Estimated EGR Rate Too High

SET CONDITIONS:
The PCI ECU (D420) detects that the calculated EGR gas mass flow is too high.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine speed is above 1100 rpm.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Contaminated EGR pressure difference sensor venturi
2. EGR pressure difference sensor deviation
3. EGR temperature sensor deviation

ADDITIONAL INFORMATION:
1. The engine NOx emission is, among others, controlled by varying the EGR gas mass flow toward the inlet manifold of the engine.
2. The EGR gas mass flow is calculated using the EGR pressure difference sensor (F751), EGR temperature sensor (F749) and boost temperature sensor (F804).
3. EGR gas mass flow toward the inlet manifold of the engine is controlled by the EGR valve module (L095).

IMPORTANT: The EGR valve position does not just indicate the amount of EGR flow to the inlet manifold. The amount of EGR gas fed back mainly depends on the pressure difference between the pressure before turbine and the boost pressure, in combination with the EGR valve position.SET CONDITIONS:
The PCI ECU (D420) detects that the calculated EGR gas mass flow is too high.

DIAGNOSTIC CONDITION:
This diagnostic runs when the engine speed is above 1100 rpm.

CORRESPONDING OBD READINESS MONITOR:
None

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

REPAIR VERIFICATION:
1. Clear all DTCs.
2. Test drive or operate the vehicle to meet the diagnostic conditions and set conditions.
3. Did the DTC come back? (Can be pending, inactive or active)
– No, repair successful
– Yes, repair unsuccessful

POSSIBLE CAUSES:
1. Contaminated EGR pressure difference sensor venturi
2. EGR pressure difference sensor deviation
3. EGR temperature sensor deviation

ADDITIONAL INFORMATION:
1. The engine NOx emission is, among others, controlled by varying the EGR gas mass flow toward the inlet manifold of the engine.
2. The EGR gas mass flow is calculated using the EGR pressure difference sensor (F751), EGR temperature sensor (F749) and boost temperature sensor (F804).
3. EGR gas mass flow toward the inlet manifold of the engine is controlled by the EGR valve module (L095).

IMPORTANT: The EGR valve position does not just indicate the amount of EGR flow to the inlet manifold. The amount of EGR gas fed back mainly depends on the pressure difference between the pressure before turbine and the boost pressure, in combination with the EGR valve position.