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Diagnostic Trouble Code (DTC) P0401
Exhaust Gas Recirculation Insufficient Flow
Circuit Details
Time for setting the DTC |
Task boosted after DTC sets |
When will DTC clear? |
DTC sets when 1) Barometric Pressure (BARO) > 72 kPa (10.4 psi). |
1) The Malfunction Indicator Lamp (MIL) will not glow. |
1) The MIL will turn off after four consecutive ignition cycles in which the diagnostic runs without a fault. |
2) Vehicle speed > 20 km/h (12.4 mph) (SOHC). |
2) The ECM will begin to store conditions which were present when the DTC failed. |
2) De-linking the ECM battery feed for 10 seconds. |
3) Vehicle speed > 18 km/h (11.2 mph) (DOHC). |
3) This information will not be recorded in the Freeze Frame. |
3) The scan tool can be used to remove all existing DTCs. |
4) A/C clutch/transmission remains unaltered. |
4) A history DTC will be stored. |
- |
5) Rpm dwells round 1600 and 3200 for manual transaxle (SOHC). |
5) EGR will be disabled. |
- |
6) The EGR is > 10% Rpm dwells round 1400 and 3000 for manual transaxle (DOHC). |
- |
- |
7) Rpm dwells round 1300 and 2900 for automatic transaxle (DOHC). |
- |
- |
8) Compensated MAP is with 10 to 50 kpa (1.5 to 7.3 psi) range (SOHC). |
- |
- |
9) DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0351, P0352, P0402, P0404, P1404, P0405, P0406 and P0502 are NOT SET. |
- |
- |
10) Test in Decel Fuel Cutoff (DFCO) mode. |
- |
- |
11) Compensated MAP is with 10.3 to 32 kpa (1.5 to 4.6 psi) range (DOHC). |
- |
- |
When will test begin? |
When will test end? |
1) Throttle position (TP) sensor below 1%. |
1) Change in vehicle speed > 8km/h (4.9 mph) (SOHC). |
2) EGR not exceeding 1%. |
2) Change in vehicle speed > 4km/h (2.5 mph) (DOHC). |
3) Change in MAP < 1.0 kpa (0.15 psi). |
3) Rpm > 50. |
4) Idle airflow < 15 kpa (2.2 psi) (SOHC). |
4) EGR opened < 90% commanded position. |
Diagnostic Tools
Purpose of the Test
Number(s) below refer to the step number(s) on the Diagnostic Table.
1-The On-Board Diagnostic (EOBD) System Check assists the technician to finish some routine checks and store the freeze frame and failure records data on the scan tool if applicable. An electronic copy of the data is obtained when the malfunction occurs and this data is then stored on the scan tool for future use.
2-In this step the EGR valve open is directed to ensure if the EGR system is completely restricted or partly restricted.
3- Here we visually or manually check the EGR passages and valve and see if there are excessive carbon deposits or damage present.
4- Here we ensure that all gasket materials are removed from the EGR mounting surface. A wee amount of material can also cause a DTC P0401 to set.
5-This step confirms whether there is any error and also testifies if a repair solved the problem. If you see that the EGR Deceleration Filter value settles near 0 or a positive number after several tests have been run, then a small restriction may still remain. You must look up the EGR pipe to fish out any damage or dents and also the EGR valve and see if any excessive carbon builds up is there. Only 1 test per ignition cycle should make it perform unless a DTC P0401 has been cleared or the battery de-linked.
6- A very essential step for this diagnostic is to clear the DTC. No sooner it is cleared than the it allows the EGR valve to get a new pintle position since the existing pintle position was flawed because of a failure that initiated the DTC. The DTC needs to be unset keeping the ignition ON, and the engine OFF or when the engine is idling. However the new pintle will not be obtained in case the ECM sees an EGR command.
HOW TO CLEAR A DTC
DTC P0401 - Exhaust Gas Recirculation Insufficient Flow
Step |
Task |
Positive |
Negative |
1 |
Carry out the EOBD System check. Is the test done? |
Follow Step 2 |
Follow "On-Board Diagnostic System Check" |
2 |
Note: The value at this point must be 50% Do you see that the engine stalls or attempts to stall? |
Follow Step 5 |
Follow Step 3 |
3 |
Task done? |
Follow Step 5 |
Follow Step 4 |
4 |
Change the EGR valve. Did you change it? |
Follow Step 5 |
- |
5 |
Note: The value at this point must be 0. Do you note that the EGR Decel Filter value >0? |
Follow Step 3 |
Follow Step 6 |
6 |
Do you see that the scan tool reads that this diagnostic has been run and passed? |
Follow Step 7 |
Follow Step 2 |
7 |
Inspect to see if there is any additional DTCs set. Do you see any DTCs displayed that have not been diagnosed? |
Go to Applicable DTC table |
The system of your vehicle is fine. |