Suzuki Wagon R Manual page 405

6-66 ENGINE DIAGNOSIS
DTC P0171 FUEL SYSTEM TOO LEAN
DTC P0172 FUEL SYSTEM TOO RICH
CIRCUIT DESCRIPTION
Sensed
information
Fuel injector
A / F mixture
Fuse box
Ignition
switch
Relay box
Main
fuse
DTC DETECTING CONDITION
D When following condition occurs while engine running under
closed loop condition.
– Air/fuel ratio too lean
Total fuel trim (short and long terms added) is
more than 30%
or
– Air/fuel ratio too rich
(Total fuel trim is less than –30%)
: 2 driving cycle detection logic, continuous monitoring.
Exhaust gas
Main relay
No.1 injector
No.2 injector
No.3 injector
No.4 injector
To ignition
switch
Signal to decrease amount of fuel injection
Signal to increase amount of fuel injection
High voltage
Low voltage
INJECTOR
A / F mixture Oxygen
becomes concentration
richer decreases
A / F mixture Oxygen
becomes concentration
leaner increases
To other sensor
POSSIBLE CAUSE
D Vacuum leaks (air drawn in).
D Exhaust gas leakage.
D Heated oxygen sensor-1 circuit
malfunction.
D Fuel pressure out of specification.
D Fuel injector malfunction (clogged or
leakage).
D MAP sensor poor performance.
D ECT sensor poor performance.
D IAT sensor poor performance.
D TP sensor poor performance.
D EVAP control system malfunction.
D PCV valve malfunction.
HEATED
OXYGEN
SENSOR-1