Dtc P0401 Exhaust Gas Recirculation (Egr) Insufficient Flow - Daewoo CIELO EURO III Manual

Diagnostic Aids
The EGR Decel Filter value can be a great aid in deter-
mining if a problem exists and to verify repairs. The EGR
Decel Filter is an average of the difference in the ex-
pected MAP change and the actual MAP change
caused by opening the EGR valve during a deceleration.
By driving the vehicle up to approximately 60 mph
(97 km/h) and decelerating to 20 mph (32 km/h), it can
be determined if the EGR system is OK, partially re-
stricted, or fully restricted.
A more negative number (less than *3) indicates that
the system is working normally, whereas a positive num-
ber indicates that the system is being restricted and that
the expected amount of EGR flow is was not seen. A
number that falls between negative 3 and positive 2 indi-
cates that the system is partially restricted but not re-
stricted enough to cause an emissions impact.
The EGR Decel Filter value should always be a *3 or
lower. If the EGR Decel Filter number becomes more
positive (towards 0 or more), then the EGR system is
becoming restricted. Look for possible damage to the
EGR pipe or for a restriction caused by carbon deposits
in the EGR passages or on the EGR valve.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Table.
1. The On-Board Diagnostic (EOBD) System Check
prompts the technician to complete some basic
checks and to store the freeze frame and failure re-

DTC P0401 Exhaust Gas Recirculation (EGR) Insufficient Flow

Step
Perform an On-Board Diagnostic (EOBD) System
Check.
1
Is the system check complete?
1. Start the engine and allow the engine to idle.
2. Install a scan tool.
2
3. Command the exhaust gas recirculation (EGR)
valve to the specified value.
Does the engine stall or attempt to stall.
1. Turn the engine OFF.
2. Remove the EGR valve assembly.
3
3. Inspect the EGR valve, passages and pipe for a
restriction or damage and repair as necessary.
Is a repair necessary?
Replace the EGR valve.
4
Is the action complete?
DAEWOO T-154 BL2,3
Action
ENGINE CONTROLS 1F – 297
cords data on the scan tool if applicable. This
creates an electronic copy of the data taken when
the malfunction occurred. The information is then
stored on the scan tool for later reference.
2. Commanding the EGR valve open determines
whether the EGR system is totally restricted or par-
tially restricted.
3. Visually and physically inspect the EGR passages
and valve for excessive carbon deposits or damage.
4. Be sure all gasket material is removed from the EGR
mounting surface. Even a small amount of material
may cause a DTC P0401 to set.
5. This step verifies if the fault is present and if a repair
corrected the problem. If the EGR Decel Filter value
stays near 0 or a positive number after several tests
have been run, then a small restriction may still exist.
Be sure to check the EGR pipe for damage or dents
and the EGR valve for any excessive carbon build
up. Only 1 test per ignition cycle will run unless a
DTC P0401 has been cleared or the battery has
been disconnected.
6. Clearing DTCs is a very important step for this diag-
nostic. The clearing function allows the EGR valve to
relearn a new pintle position as the old pintle position
was inaccurate due to the failure that caused the
DTC. The DTC must be cleared with the ignition ON,
engine OFF or when the engine is idling. If the
ECM sees a EGR command, the new pintle will not
be learned.
Value
–
Go to Step 2
50% Go to Step 5
–
Go to Step 5
– Go to Step 5
Yes No
Go to
"On-Board
Diagnostic
System Check"
Go to Step 3
Go to Step 4
–