2014 Jeep Wrangler JK Factory Service Manual 28 - DTC-Based Diagnostics

P0401-EGR FLOW INSUFFICIENT DETECTED

Special Tools: Click to display a list of tools used in this procedure


For a complete wiring diagram, refer to the Wiring Information.


Theory of Operation

The EGR Airflow Control Valve is a pulse width modulated output, controlled by the Powertrain Control Module (PCM). The EGR Airflow Control Valve is used to control the ratio of fresh air flow to EGR gas air flow. The PCM monitors this ratio with the Mass Air Flow Sensor. The Mass Air Flow Sensor feedback is very prominent in determining the position of the EGR Airflow Control Valve. If the Mass Air Flow Sensor feedback does not match what the PCM is expecting to see when EGR air flow is requested, it can effect the operation of the EGR Valve and the EGR Airflow Control Valve. This can occur if the Mass Air Flow Sensor feedback is faulty or inaccurate, even if no DTCs are actively set. The EGR system and Diesel Particulate Filter regeneration is disabled when the fault is active.



Possible Causes

AIR FILTER
INTAKE SYSTEM AIR LEAKS OR RESTRICTIONS
EGR AIR FLOW CONTROL VALVE
EGR COOLER AND TUBES RESTRICTED
EGR VALVE

1. CHECK FOR ACTIVE DTC



NOTE: If the PCM detects and stores a DTC, the PCM also stores the operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed. Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for an active DTC.

NOTE: If there are any Mass Air Flow DTCs present, diagnose the MAF DTCs before continuing EGR diagnostics.
1. Turn the ignition on.
2. With the scan tool, erase PCM DTCs.
3. Test drive the vehicle and monitor the scan tool for PCM DTCs.


Did this DTC return?

Yes


No


2. AIR FILTER

1. Turn the ignition off.
2. Remove and inspect the Air Filter for soiling or excessive dirt and debris which may cause air flow restriction.


Were any of these problems found?

Yes


No


3. AIR RESTRICTION

1. Visually inspect the fresh air inlet tube for a blockage due to snow, ice or dirt buildup.
2. Visually inspect the intake system, exhaust system and related tubes and connections.


NOTE: Inspect all air intake, crankcase vent and Turbocharger related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.

NOTE: Inspect the exhaust system and related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.


Were any problems found?

Yes


No


4. CHECK FOR AIR LEAKS

1. Remove the Inlet Pressure Sensor.
2. Connect Evaporative Emissions Leak Detector Kit, EELD And Accessory 8404C to the Inlet Pressure Sensor port in the intake duct and begin injecting smoke into the intake system.
3. Observe all intake system components for evidence of smoke leakage.


Is there evidence of a leak?

Yes


No


5. CHECK THE EGR AIR FLOW CONTROL VALVE

1. Disconnect the air tube at the inlet port of the EGR Air Flow Control Valve.
2. Use a mirror to observe the motion of the EGR Air Flow Control Valve.
3. Turn the ignition on.
4. The EGR Air Flow Control Valve should open completely without binding with the ignition on.


NOTE: Cycle the ignition on and off several times while observing the operation of the valve.


Did the EGR Air Flow Control Valve operate correctly and without binding?

Yes


No


6. CHECK THE EGR COOLER AND TUBES

1. Turn the ignition off.
2. Gain access to and inspect the EGR Cooler and both tubes that connect to the EGR Cooler. Check tubes and cooler for damage, leaks, excessive soot build up and other problems that could restrict or prevent proper exhaust gas flow.


NOTE: Compressed air (at low pressure) can be applied to the lower port of the EGR Cooler. When applying compressed air check for air to flow through cooler and out the upper port. Always wear safety glasses when working with compressed air.


Were any problems found?

Yes


No