DTC P0401 [L3 Turbo]

id0102b7815300

DTC P0401

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 is available.

•  The DTC is stored in the PCM memory.

POSSIBLE CAUSE

•  Vacuum hose looseness or damage

•  EGR valve malfunction

•  MAP sensor malfunction

•  EGR gasket malfunction

•  PCM malfunction

DTC P0401	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 is available. • The DTC is stored in the PCM memory.
POSSIBLE CAUSE	• Vacuum hose looseness or damage • EGR valve malfunction • MAP sensor malfunction • EGR gasket malfunction • PCM malfunction

Diagnostic procedure

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR 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	INSPECT FOR OTHER DTCS • Connect the M-MDS to the DLC-2. • Clear the DTC from the PCM memory using the M-MDS. • Turn the ignition switch off then to the ON position (engine off). • Have other DTCs been stored?	Yes	Repair the circuit malfunction for applicable DTCs. (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 EGR VALVE MALFUNCTION • Inspect the EGR valve. (See EGR VALVE INSPECTION [L3 Turbo].) • Is there any malfunction?	Yes	Replace the EGR valve, then go to Step 8. (See EGR VALVE REMOVAL/INSTALLATION [L3 Turbo].)
5		No	Go to the next step.
6	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, then go to Step 8. (See MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR/BOOST AIR TEMPERATURE SENSOR REMOVAL/INSTALLATION [L3 Turbo].)
6		No	Go to the next step.
7	INSPECT EGR VALVE PASSAGE • Turn the ignition switch off. • Remove the EGR valve. (See EGR VALVE REMOVAL/INSTALLATION [L3 Turbo].) • Is the gasket installation normal?	Yes	Go to the next step.
7		No	Install the gasket correctly, then go to the next step.
8	VERIFY TROUBLESHOOTING OF DTC P0401 COMPLETED • Make sure to reconnect all disconnected connectors. • Connect the M-MDS to the DLC-2. • Clear the DTC from the PCM memory using the M-MDS. • Perform the KOER self test. (See KOEO/KOER SELF TEST [L3 Turbo].) • Is the same DTC present?	Yes	Go to the next step.
8		No	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L3 Turbo].)
9	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].)
9		No	Troubleshooting completed.