Code
P0401
AUDI
P — Powertrain
Restriction in the EGR passages usually caused by carbon buildup, The EGR Valve is defective, Lack of proper vacuum or electrical signal to the EGR valve, Malfunctioning EGR Vacuum supply solenoid, Lack of proper EGR system feedback to the computer from the: Manifold Absolute Pressure Sensor (MAP), Differential EGR Pressure Feedback Sensor (DPFE), EGR Valve Position Sensor (EVP), EGR Temperature Sensor
Views:
UK: 33
EN: 50
RU: 93
AI status
Completed
Completed
100%
Causes
- Carbon buildup/clogged EGR passages or EGR cooler
- EGR valve stuck closed or mechanically seized
- Failed EGR valve (electrical or vacuum-actuated)
- Faulty EGR vacuum supply solenoid or hose leaks (vacuum systems)
- Loss of electrical drive to EGR actuator (wiring, connector, fuse)
- Defective or incorrect feedback from MAP, DPFE (differential pressure), EGR valve position sensor, or EGR temperature sensor
Symptoms
- Check Engine Light (MIL) illuminated; code P0401 stored
- Poor idle, hesitation or stumble under light load
- Slight roughness or increased NOx emissions
- Possible reduced fuel economy or increased combustion knock under some conditions
- Engine may run normally at wide-open-throttle (EGR usually disabled at WOT)
What to check
- Read freeze-frame data and confirming operating conditions when code set (engine temp, load, RPM, commanded EGR duty)
- Use scan tool to command EGR open/closed and observe live data (EGR position, DPFE, MAP, EGR temp)
- Visually inspect EGR valve, actuator, solenoid, vacuum hoses and electrical connectors for damage or leaks
- Check vacuum supply (if vacuum system) for presence and leakage under command
- Backprobe and monitor EGR valve position sensor or actuator signal during commanded cycles
- Inspect and test DPFE/differential pressure or MAP sensor signals for plausibility
Signal parameters
- EGR commanded vs actual: when commanded open, EGR position signal should change and remain stable
- DPFE/differential pressure: should show increased differential when EGR is commanded open
- MAP: small drop in manifold absolute pressure or transient change when EGR opens at part load
- EGR temperature (if equipped): downstream temp should rise slightly when hot exhaust gas is recirculated
- Vacuum at EGR (vacuum systems): vacuum present when solenoid energized/commanded
- EGR solenoid coil supply: 12 V supply and switching ground from ECM when commanded (verify with meter/scan tool)
Diagnostic algorithm
- Verify the code and capture freeze-frame data. Note engine coolant temp, load, RPM and conditions when P0401 set.
- With a capable scan tool, command the EGR valve open/closed while monitoring EGR position, DPFE (or MAP), and EGR temp. Observe whether feedback changes as commanded.
- If EGR does not move when commanded, check actuator type: for vacuum systems test vacuum source and control solenoid; for electronic actuators check power, ground and control signal with connector connected.
- Inspect wiring and connectors for corrosion, broken wires, or pins pushed out. Wiggle-test while monitoring live data to detect intermittent faults.
- Inspect EGR valve and passages for carbon buildup. Remove valve for visual check and clean passages if clogged. On vehicles with EGR coolers, inspect cooler for blockage.
- Test DPFE/differential pressure or MAP sensor operation: compare sensor response to commanded EGR and known-good patterns. Replace sensor if out of range or nonresponsive.
- If cleaning restores movement but code returns, consider replacing EGR valve/actuator or EGR cooler as needed. After repair clear codes and perform a road test under conditions that previously set the code.
- If all hardware and sensors test OK but ECM logic persists, verify software updates/TSBs for EGR strategy; consult manufacturer procedures before replacing ECM.
Likely causes
- Carbon/clogging in valve, passages, or EGR cooler (most common)
- EGR valve not actuating due to failed solenoid or vacuum supply
- Wiring/connectors to EGR actuator or feedback sensors are damaged or corroded
- DPFE/differential pressure sensor or MAP sensor giving incorrect readings
- EGR valve position sensor failed or out of tolerance
Fault status
Status
P0401 — Insufficient exhaust gas recirculation flow detected. ECM commanded EGR but measured EGR flow/feedback is below expected threshold. Inspect EGR valve, passages, control solenoid/vacuum, and feedback sensors (DPFE/MAP/EGR position/temperature).
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0401
Generic
P — Powertrain
EGR A Flow Insufficient Detected
Views:
UK: 34
EN: 332
RU: 106
AI status
Completed
Completed
100%
Causes
- Carbon buildup/clogged EGR passages or EGR cooler
- EGR valve stuck closed or mechanically seized
- Failed EGR valve (electrical or vacuum-actuated)
- Faulty EGR vacuum supply solenoid or hose leaks (vacuum systems)
- Loss of electrical drive to EGR actuator (wiring, connector, fuse)
- Defective or incorrect feedback from MAP, DPFE (differential pressure), EGR valve position sensor, or EGR temperature sensor
Symptoms
- Check Engine Light (MIL) illuminated; code P0401 stored
- Poor idle, hesitation or stumble under light load
- Slight roughness or increased NOx emissions
- Possible reduced fuel economy or increased combustion knock under some conditions
- Engine may run normally at wide-open-throttle (EGR usually disabled at WOT)
What to check
- Read freeze-frame data and confirming operating conditions when code set (engine temp, load, RPM, commanded EGR duty)
- Use scan tool to command EGR open/closed and observe live data (EGR position, DPFE, MAP, EGR temp)
- Visually inspect EGR valve, actuator, solenoid, vacuum hoses and electrical connectors for damage or leaks
- Check vacuum supply (if vacuum system) for presence and leakage under command
- Backprobe and monitor EGR valve position sensor or actuator signal during commanded cycles
- Inspect and test DPFE/differential pressure or MAP sensor signals for plausibility
Signal parameters
- EGR commanded vs actual: when commanded open, EGR position signal should change and remain stable
- DPFE/differential pressure: should show increased differential when EGR is commanded open
- MAP: small drop in manifold absolute pressure or transient change when EGR opens at part load
- EGR temperature (if equipped): downstream temp should rise slightly when hot exhaust gas is recirculated
- Vacuum at EGR (vacuum systems): vacuum present when solenoid energized/commanded
- EGR solenoid coil supply: 12 V supply and switching ground from ECM when commanded (verify with meter/scan tool)
Diagnostic algorithm
- Verify the code and capture freeze-frame data. Note engine coolant temp, load, RPM and conditions when P0401 set.
- With a capable scan tool, command the EGR valve open/closed while monitoring EGR position, DPFE (or MAP), and EGR temp. Observe whether feedback changes as commanded.
- If EGR does not move when commanded, check actuator type: for vacuum systems test vacuum source and control solenoid; for electronic actuators check power, ground and control signal with connector connected.
- Inspect wiring and connectors for corrosion, broken wires, or pins pushed out. Wiggle-test while monitoring live data to detect intermittent faults.
- Inspect EGR valve and passages for carbon buildup. Remove valve for visual check and clean passages if clogged. On vehicles with EGR coolers, inspect cooler for blockage.
- Test DPFE/differential pressure or MAP sensor operation: compare sensor response to commanded EGR and known-good patterns. Replace sensor if out of range or nonresponsive.
- If cleaning restores movement but code returns, consider replacing EGR valve/actuator or EGR cooler as needed. After repair clear codes and perform a road test under conditions that previously set the code.
- If all hardware and sensors test OK but ECM logic persists, verify software updates/TSBs for EGR strategy; consult manufacturer procedures before replacing ECM.
Likely causes
- Carbon/clogging in valve, passages, or EGR cooler (most common)
- EGR valve not actuating due to failed solenoid or vacuum supply
- Wiring/connectors to EGR actuator or feedback sensors are damaged or corroded
- DPFE/differential pressure sensor or MAP sensor giving incorrect readings
- EGR valve position sensor failed or out of tolerance
Fault status
Status
P0401 — Insufficient exhaust gas recirculation flow detected. ECM commanded EGR but measured EGR flow/feedback is below expected threshold. Inspect EGR valve, passages, control solenoid/vacuum, and feedback sensors (DPFE/MAP/EGR position/temperature).
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0401
GWM
P — Powertrain
- Exhaust gas recirculation system too low
Views:
UK: 10
EN: 17
RU: 30
AI status
Completed
Completed
100%
Causes
- Carbon buildup/clogged EGR passages or EGR cooler
- EGR valve stuck closed or mechanically seized
- Failed EGR valve (electrical or vacuum-actuated)
- Faulty EGR vacuum supply solenoid or hose leaks (vacuum systems)
- Loss of electrical drive to EGR actuator (wiring, connector, fuse)
- Defective or incorrect feedback from MAP, DPFE (differential pressure), EGR valve position sensor, or EGR temperature sensor
Symptoms
- Check Engine Light (MIL) illuminated; code P0401 stored
- Poor idle, hesitation or stumble under light load
- Slight roughness or increased NOx emissions
- Possible reduced fuel economy or increased combustion knock under some conditions
- Engine may run normally at wide-open-throttle (EGR usually disabled at WOT)
What to check
- Read freeze-frame data and confirming operating conditions when code set (engine temp, load, RPM, commanded EGR duty)
- Use scan tool to command EGR open/closed and observe live data (EGR position, DPFE, MAP, EGR temp)
- Visually inspect EGR valve, actuator, solenoid, vacuum hoses and electrical connectors for damage or leaks
- Check vacuum supply (if vacuum system) for presence and leakage under command
- Backprobe and monitor EGR valve position sensor or actuator signal during commanded cycles
- Inspect and test DPFE/differential pressure or MAP sensor signals for plausibility
Signal parameters
- EGR commanded vs actual: when commanded open, EGR position signal should change and remain stable
- DPFE/differential pressure: should show increased differential when EGR is commanded open
- MAP: small drop in manifold absolute pressure or transient change when EGR opens at part load
- EGR temperature (if equipped): downstream temp should rise slightly when hot exhaust gas is recirculated
- Vacuum at EGR (vacuum systems): vacuum present when solenoid energized/commanded
- EGR solenoid coil supply: 12 V supply and switching ground from ECM when commanded (verify with meter/scan tool)
Diagnostic algorithm
- Verify the code and capture freeze-frame data. Note engine coolant temp, load, RPM and conditions when P0401 set.
- With a capable scan tool, command the EGR valve open/closed while monitoring EGR position, DPFE (or MAP), and EGR temp. Observe whether feedback changes as commanded.
- If EGR does not move when commanded, check actuator type: for vacuum systems test vacuum source and control solenoid; for electronic actuators check power, ground and control signal with connector connected.
- Inspect wiring and connectors for corrosion, broken wires, or pins pushed out. Wiggle-test while monitoring live data to detect intermittent faults.
- Inspect EGR valve and passages for carbon buildup. Remove valve for visual check and clean passages if clogged. On vehicles with EGR coolers, inspect cooler for blockage.
- Test DPFE/differential pressure or MAP sensor operation: compare sensor response to commanded EGR and known-good patterns. Replace sensor if out of range or nonresponsive.
- If cleaning restores movement but code returns, consider replacing EGR valve/actuator or EGR cooler as needed. After repair clear codes and perform a road test under conditions that previously set the code.
- If all hardware and sensors test OK but ECM logic persists, verify software updates/TSBs for EGR strategy; consult manufacturer procedures before replacing ECM.
Likely causes
- Carbon/clogging in valve, passages, or EGR cooler (most common)
- EGR valve not actuating due to failed solenoid or vacuum supply
- Wiring/connectors to EGR actuator or feedback sensors are damaged or corroded
- DPFE/differential pressure sensor or MAP sensor giving incorrect readings
- EGR valve position sensor failed or out of tolerance
Fault status
Status
P0401 — Insufficient exhaust gas recirculation flow detected. ECM commanded EGR but measured EGR flow/feedback is below expected threshold. Inspect EGR valve, passages, control solenoid/vacuum, and feedback sensors (DPFE/MAP/EGR position/temperature).
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0401
HUMMER
P — Powertrain
Exhaust Gas Recirculation (EGR) Flow Insufficient
Views:
UK: 14
EN: 32
RU: 66
AI status
Completed
Completed
100%
Causes
- Carbon buildup/clogged EGR passages or EGR cooler
- EGR valve stuck closed or mechanically seized
- Failed EGR valve (electrical or vacuum-actuated)
- Faulty EGR vacuum supply solenoid or hose leaks (vacuum systems)
- Loss of electrical drive to EGR actuator (wiring, connector, fuse)
- Defective or incorrect feedback from MAP, DPFE (differential pressure), EGR valve position sensor, or EGR temperature sensor
Symptoms
- Check Engine Light (MIL) illuminated; code P0401 stored
- Poor idle, hesitation or stumble under light load
- Slight roughness or increased NOx emissions
- Possible reduced fuel economy or increased combustion knock under some conditions
- Engine may run normally at wide-open-throttle (EGR usually disabled at WOT)
What to check
- Read freeze-frame data and confirming operating conditions when code set (engine temp, load, RPM, commanded EGR duty)
- Use scan tool to command EGR open/closed and observe live data (EGR position, DPFE, MAP, EGR temp)
- Visually inspect EGR valve, actuator, solenoid, vacuum hoses and electrical connectors for damage or leaks
- Check vacuum supply (if vacuum system) for presence and leakage under command
- Backprobe and monitor EGR valve position sensor or actuator signal during commanded cycles
- Inspect and test DPFE/differential pressure or MAP sensor signals for plausibility
Signal parameters
- EGR commanded vs actual: when commanded open, EGR position signal should change and remain stable
- DPFE/differential pressure: should show increased differential when EGR is commanded open
- MAP: small drop in manifold absolute pressure or transient change when EGR opens at part load
- EGR temperature (if equipped): downstream temp should rise slightly when hot exhaust gas is recirculated
- Vacuum at EGR (vacuum systems): vacuum present when solenoid energized/commanded
- EGR solenoid coil supply: 12 V supply and switching ground from ECM when commanded (verify with meter/scan tool)
Diagnostic algorithm
- Verify the code and capture freeze-frame data. Note engine coolant temp, load, RPM and conditions when P0401 set.
- With a capable scan tool, command the EGR valve open/closed while monitoring EGR position, DPFE (or MAP), and EGR temp. Observe whether feedback changes as commanded.
- If EGR does not move when commanded, check actuator type: for vacuum systems test vacuum source and control solenoid; for electronic actuators check power, ground and control signal with connector connected.
- Inspect wiring and connectors for corrosion, broken wires, or pins pushed out. Wiggle-test while monitoring live data to detect intermittent faults.
- Inspect EGR valve and passages for carbon buildup. Remove valve for visual check and clean passages if clogged. On vehicles with EGR coolers, inspect cooler for blockage.
- Test DPFE/differential pressure or MAP sensor operation: compare sensor response to commanded EGR and known-good patterns. Replace sensor if out of range or nonresponsive.
- If cleaning restores movement but code returns, consider replacing EGR valve/actuator or EGR cooler as needed. After repair clear codes and perform a road test under conditions that previously set the code.
- If all hardware and sensors test OK but ECM logic persists, verify software updates/TSBs for EGR strategy; consult manufacturer procedures before replacing ECM.
Likely causes
- Carbon/clogging in valve, passages, or EGR cooler (most common)
- EGR valve not actuating due to failed solenoid or vacuum supply
- Wiring/connectors to EGR actuator or feedback sensors are damaged or corroded
- DPFE/differential pressure sensor or MAP sensor giving incorrect readings
- EGR valve position sensor failed or out of tolerance
Fault status
Status
P0401 — Insufficient exhaust gas recirculation flow detected. ECM commanded EGR but measured EGR flow/feedback is below expected threshold. Inspect EGR valve, passages, control solenoid/vacuum, and feedback sensors (DPFE/MAP/EGR position/temperature).
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0401
LAND ROVER
P — Powertrain
Insufficient exhaust gas recirculation flow detected
Views:
UK: 12
EN: 29
RU: 59
AI status
Completed
Completed
100%
Causes
- Carbon buildup/clogged EGR passages or EGR cooler
- EGR valve stuck closed or mechanically seized
- Failed EGR valve (electrical or vacuum-actuated)
- Faulty EGR vacuum supply solenoid or hose leaks (vacuum systems)
- Loss of electrical drive to EGR actuator (wiring, connector, fuse)
- Defective or incorrect feedback from MAP, DPFE (differential pressure), EGR valve position sensor, or EGR temperature sensor
Symptoms
- Check Engine Light (MIL) illuminated; code P0401 stored
- Poor idle, hesitation or stumble under light load
- Slight roughness or increased NOx emissions
- Possible reduced fuel economy or increased combustion knock under some conditions
- Engine may run normally at wide-open-throttle (EGR usually disabled at WOT)
What to check
- Read freeze-frame data and confirming operating conditions when code set (engine temp, load, RPM, commanded EGR duty)
- Use scan tool to command EGR open/closed and observe live data (EGR position, DPFE, MAP, EGR temp)
- Visually inspect EGR valve, actuator, solenoid, vacuum hoses and electrical connectors for damage or leaks
- Check vacuum supply (if vacuum system) for presence and leakage under command
- Backprobe and monitor EGR valve position sensor or actuator signal during commanded cycles
- Inspect and test DPFE/differential pressure or MAP sensor signals for plausibility
Signal parameters
- EGR commanded vs actual: when commanded open, EGR position signal should change and remain stable
- DPFE/differential pressure: should show increased differential when EGR is commanded open
- MAP: small drop in manifold absolute pressure or transient change when EGR opens at part load
- EGR temperature (if equipped): downstream temp should rise slightly when hot exhaust gas is recirculated
- Vacuum at EGR (vacuum systems): vacuum present when solenoid energized/commanded
- EGR solenoid coil supply: 12 V supply and switching ground from ECM when commanded (verify with meter/scan tool)
Diagnostic algorithm
- Verify the code and capture freeze-frame data. Note engine coolant temp, load, RPM and conditions when P0401 set.
- With a capable scan tool, command the EGR valve open/closed while monitoring EGR position, DPFE (or MAP), and EGR temp. Observe whether feedback changes as commanded.
- If EGR does not move when commanded, check actuator type: for vacuum systems test vacuum source and control solenoid; for electronic actuators check power, ground and control signal with connector connected.
- Inspect wiring and connectors for corrosion, broken wires, or pins pushed out. Wiggle-test while monitoring live data to detect intermittent faults.
- Inspect EGR valve and passages for carbon buildup. Remove valve for visual check and clean passages if clogged. On vehicles with EGR coolers, inspect cooler for blockage.
- Test DPFE/differential pressure or MAP sensor operation: compare sensor response to commanded EGR and known-good patterns. Replace sensor if out of range or nonresponsive.
- If cleaning restores movement but code returns, consider replacing EGR valve/actuator or EGR cooler as needed. After repair clear codes and perform a road test under conditions that previously set the code.
- If all hardware and sensors test OK but ECM logic persists, verify software updates/TSBs for EGR strategy; consult manufacturer procedures before replacing ECM.
Likely causes
- Carbon/clogging in valve, passages, or EGR cooler (most common)
- EGR valve not actuating due to failed solenoid or vacuum supply
- Wiring/connectors to EGR actuator or feedback sensors are damaged or corroded
- DPFE/differential pressure sensor or MAP sensor giving incorrect readings
- EGR valve position sensor failed or out of tolerance
Fault status
Status
P0401 — Insufficient exhaust gas recirculation flow detected. ECM commanded EGR but measured EGR flow/feedback is below expected threshold. Inspect EGR valve, passages, control solenoid/vacuum, and feedback sensors (DPFE/MAP/EGR position/temperature).
Repair difficulty: Medium
Diagnostic time: 1-4 hours
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Code
P0401
MITSUBISHI
P — Powertrain
EGR flow insufficient
Views:
UK: 17
EN: 34
RU: 70
AI status
Completed
Completed
100%
Causes
- Carbon buildup/clogged EGR passages or EGR cooler
- EGR valve stuck closed or mechanically seized
- Failed EGR valve (electrical or vacuum-actuated)
- Faulty EGR vacuum supply solenoid or hose leaks (vacuum systems)
- Loss of electrical drive to EGR actuator (wiring, connector, fuse)
- Defective or incorrect feedback from MAP, DPFE (differential pressure), EGR valve position sensor, or EGR temperature sensor
Symptoms
- Check Engine Light (MIL) illuminated; code P0401 stored
- Poor idle, hesitation or stumble under light load
- Slight roughness or increased NOx emissions
- Possible reduced fuel economy or increased combustion knock under some conditions
- Engine may run normally at wide-open-throttle (EGR usually disabled at WOT)
What to check
- Read freeze-frame data and confirming operating conditions when code set (engine temp, load, RPM, commanded EGR duty)
- Use scan tool to command EGR open/closed and observe live data (EGR position, DPFE, MAP, EGR temp)
- Visually inspect EGR valve, actuator, solenoid, vacuum hoses and electrical connectors for damage or leaks
- Check vacuum supply (if vacuum system) for presence and leakage under command
- Backprobe and monitor EGR valve position sensor or actuator signal during commanded cycles
- Inspect and test DPFE/differential pressure or MAP sensor signals for plausibility
Signal parameters
- EGR commanded vs actual: when commanded open, EGR position signal should change and remain stable
- DPFE/differential pressure: should show increased differential when EGR is commanded open
- MAP: small drop in manifold absolute pressure or transient change when EGR opens at part load
- EGR temperature (if equipped): downstream temp should rise slightly when hot exhaust gas is recirculated
- Vacuum at EGR (vacuum systems): vacuum present when solenoid energized/commanded
- EGR solenoid coil supply: 12 V supply and switching ground from ECM when commanded (verify with meter/scan tool)
Diagnostic algorithm
- Verify the code and capture freeze-frame data. Note engine coolant temp, load, RPM and conditions when P0401 set.
- With a capable scan tool, command the EGR valve open/closed while monitoring EGR position, DPFE (or MAP), and EGR temp. Observe whether feedback changes as commanded.
- If EGR does not move when commanded, check actuator type: for vacuum systems test vacuum source and control solenoid; for electronic actuators check power, ground and control signal with connector connected.
- Inspect wiring and connectors for corrosion, broken wires, or pins pushed out. Wiggle-test while monitoring live data to detect intermittent faults.
- Inspect EGR valve and passages for carbon buildup. Remove valve for visual check and clean passages if clogged. On vehicles with EGR coolers, inspect cooler for blockage.
- Test DPFE/differential pressure or MAP sensor operation: compare sensor response to commanded EGR and known-good patterns. Replace sensor if out of range or nonresponsive.
- If cleaning restores movement but code returns, consider replacing EGR valve/actuator or EGR cooler as needed. After repair clear codes and perform a road test under conditions that previously set the code.
- If all hardware and sensors test OK but ECM logic persists, verify software updates/TSBs for EGR strategy; consult manufacturer procedures before replacing ECM.
Likely causes
- Carbon/clogging in valve, passages, or EGR cooler (most common)
- EGR valve not actuating due to failed solenoid or vacuum supply
- Wiring/connectors to EGR actuator or feedback sensors are damaged or corroded
- DPFE/differential pressure sensor or MAP sensor giving incorrect readings
- EGR valve position sensor failed or out of tolerance
Fault status
Status
P0401 — Insufficient exhaust gas recirculation flow detected. ECM commanded EGR but measured EGR flow/feedback is below expected threshold. Inspect EGR valve, passages, control solenoid/vacuum, and feedback sensors (DPFE/MAP/EGR position/temperature).
Repair difficulty: Medium
Diagnostic time: 1-4 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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👍 Like
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Send to email