Dtc P0171 Fuel System Too Lean; Dtc P0172 Fuel System Too Rich - Suzuki Swift User Manual

6-64 ENGINE GENERAL INFORMATION AND DIAGNOSIS (TBI FOR G10)

DTC P0171 FUEL SYSTEM TOO LEAN

DTC P0172 FUEL SYSTEM TOO RICH

CIRCUIT DESCRIPTION
Sensed
information
ECM
(PCM)
Exhaust
gas
HO2S-1
Ignition switch
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.
Fuel
injector
A / F
mixture
To other circuits
"IG COIL METER"
Main relay
Injector resistor
Signal to decrease amount of fuel injection
Signal to increase amount of fuel injection
ECM
(PCM)
INJECTOR
A / F mixture
becomes
richer
A / F mixture
becomes
leaner
To other Fuel
sensor injector
Heated oxygen sensor-1
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.
High voltage
Low voltage
HEATED
OXYGEN
SENSOR-1
Oxygen
concentration
decreases
Oxygen
concentration
increases