DTC P0401:00 [L3 Turbo]

DTC P0401:00 [L3 Turbo]SM2444104

id0102b7704200

DTC P0401:00	EGR flow insufficient detected
DETECTION CONDITION	• The PCM monitors the difference in intake manifold pressures when the EGR is operated and when it is stopped. If the difference is too small, the PCM determines that the EGR flow is insufficient. Diagnostic support note • This is an intermittent monitor (EGR system). • The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM. • PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle. • FREEZE FRAME DATA (Mode 2)/Snapshot data is available. • DTCs are stored in the PCM memory.
POSSIBLE CAUSE	• Vacuum hose looseness or damage • MAP sensor malfunction • EGR valve improper operation ― EGR valve malfunction • EGR gasket malfunction • PCM malfunction

DTC P0401:00

EGR flow insufficient detected

DETECTION CONDITION

• The PCM monitors the difference in intake manifold pressures when the EGR is operated and when it is stopped. If the difference is too small, the PCM determines that the EGR flow is insufficient.

Diagnostic support note

• This is an intermittent monitor (EGR system).

• The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

• PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle.

• FREEZE FRAME DATA (Mode 2)/Snapshot data is available.

• DTCs are stored in the PCM memory.

POSSIBLE CAUSE

• Vacuum hose looseness or damage

• MAP sensor malfunction

• EGR valve improper operation

― EGR valve malfunction

• EGR gasket malfunction

• PCM malfunction

Diagnostic procedure

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA (MODE 2)/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED • Have the snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (EGR system related) been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2	VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available?	Yes	Perform repair or diagnosis according to the available Service Information. • If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	VERIFY RELATED PENDING CODE AND STORED DTC • Turn the ignition switch off, then to the ON position (engine off). • Perform the DTC Reading Procedure and Pending Trouble Code Access Procedure. (See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].) • Are any other DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [L3 Turbo].)
3		No	Go to the next step.
4	INSPECT VACUUM HOSE CONDITION • Inspect freezing vacuum hoses for clogs, damage, frozen, or vacuum leakage. • Is there any malfunction?	Yes	Replace the vacuum hoses, then go to Step 8.
4		No	Go to the next step.
5	INSPECT MAP SENSOR MALFUNCTION • Inspect the MAP sensor. (See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR INSPECTION [L3 Turbo].) • Is there any malfunction?	Yes	Replace the MAP sensor/boost air temperature sensor, then go to Step 8. (See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR/BOOST AIR TEMPERATURE SENSOR REMOVAL/INSTALLATION [L3 Turbo].)
5		No	Go to the next step.
6	INSPECT EGR VALVE OPERATION • Perform the EGR Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L3 Turbo].) • Is the EGR valve operation normally?	Yes	Go to the next step.
6		No	Repair or replace the malfunctioning part according to the inspection results, then go to Step 8.
7	INSPECT EGR VALVE PASSAGE • Turn the ignition switch off. • Remove the EGR valve. (See EGR VALVE REMOVAL/INSTALLATION [L3 Turbo].) • Visually inspect the gasket installation of EGR valve and EGR valve passage for clogging. • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to the next step.
7		No	Go to the next step.
8	MONITOR EGR SYSTEM BY DRIVE MODE • Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [L3 Turbo].) • Run the PCM Adaptive Memory Produce Drive Mode. (See OBD DRIVE MODE [L3 Turbo].) • Stop the vehicle and access the ON BOARD READINESS TEST to inspect the DRIVE MODE completion status. (See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].) • Verify the FUEL_EVAL and EGR_EVAL PIDs status. • Do the FUEL_EVAL and EGR_EVAL PIDs change to Yes?	Yes	Go to the next step.
8		No	Retry this step.
9	VERIFY DTC TROUBLESHOOTING COMPLETED • Make sure to reconnect all disconnected connectors. • Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [L3 Turbo].) • Perform the KOER self test. (See KOEO/KOER SELF TEST [L3 Turbo].) • Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L3 Turbo].)
9		No	Go to the next step.
10	VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [L3 Turbo].) • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [L3 Turbo].)
10		No	DTC troubleshooting completed.