Suzuki Swift User Manual page 221

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
ENGINE GENERAL INFORMATION AND DIAGNOSIS (SFI FOR G13) 6-1-65
Signal to decrease amount of fuel injection
Signal to increase amount of fuel injection
A / F mixture
becomes
richer
A / F mixture
becomes
leaner
To other sensor
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.
High voltage
Low voltage
Oxygen
concentration
decreases
Oxygen
concentration
increases
POSSIBLE CAUSE