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On Board Diagnosis Logic
NGEC0192
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the
theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensor 1 (front).
The ECM calculates the necessary compensation to correct the offset between the actual and the theoretical
ratios.
In case the amount of the compensation value is extremely large (The actual mixture ratio is too rich.), the
ECM judges the condition as the fuel injection system malfunction and lights up the MIL (2 trip detection logic).
Sensor Input Signal to ECM
ECM func-
tion
Actuator
Heated oxygen sensor 1 (front)
Density of oxygen in exhaust gas
(Mixture ratio feedback signal)
Fuel injec-
tion & mix-
ture ratio
control
Injectors
DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0172 쐌 Fuel injection system does not operate properly.
쐌 The amount of mixture ratio compensation is too large.
(The mixture ratio is too rich.)
쐌 Heated oxygen sensor 1 (front)
쐌 Injectors
쐌 Exhaust gas leaks
쐌 Incorrect fuel pressure
쐌 Mass air flow sensor
SEF215Z
SEF058Y
DTC Confirmation Procedure
NGEC0193
NOTE:
If “DTC Confirmation Procedure ” has been previously conducted,
always turn ignition switch OFF and wait at least 5 seconds before
conducting the next test.
With CONSULT-II
1) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch OFF and wait at least 5 seconds.
3) Turn ignition switch ON and select “SELF-LEARN CONTROL”
in “WORK SUPPORT” mode with CONSULT-II.
4) Clear the self-learning control coefficient by touching “CLEAR”.
5) Select “DATA MONITOR” mode with CONSULT-II.
6) Start engine again and let it idle for at least 10 minutes.
The 1st trip DTC P0172 should be detected at this stage, if a
malfunction exists. If so, go to “Diagnostic Procedure”,
EC-290.
7) If it is difficult to start engine at step 6, the fuel injection sys-
tem has a malfunction.
8) Crank engine while depressing accelerator pedal. If engine
starts, go to “Diagnostic Procedure”, EC-290. If engine does
not start, remove ignition plugs and check for fouling, etc.
AEC131A
With GST
1) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch OFF and wait at least 5 seconds.
3) Disconnect mass air flow sensor harness connector. Then
restart and run engine for at least 3 seconds at idle speed.
4) Stop engine and reconnect mass air flow sensor harness con-
nector.
5) Select “MODE 7” with GST. Make sure 1st trip DTC P0100 is
detected.
6) Select “MODE 4” with GST and erase the 1st trip DTC P0100.
DTC P0172 FUEL INJECTION SYSTEM FUNCTION
(RICH SIDE)
KA24DE
On Board Diagnosis Logic
EC-287
FE
CL
MT
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
GI
MA
EM
LC
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