Suzuki WagonR+ RB310 Service Manual page 1825

6-1-62 GENERAL INFORMATION AND ENGINE DIAGNOSIS
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
"IG COIL"
Main relay
"FI"
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 circuits
Fuel
injector
To other
sensors
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