Toyota Camry Manual page 1271

DI–244
DTC P0125
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three–way
catalytic converter is used, but for the most efficient use of the three–way catalytic converter, the air–fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air–fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the
stoichiometric air–fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust
gas and provide feedback to the computer for control of the air–fuel ratio.
When the air–fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the oxygen
sensor informs the ECM of the LEAN condition (small electromotive force: < 0.45 V).
When the air–fuel ratio is RICHER than the stoichiometric air–fuel ratio the oxygen concentration in the ex-
haust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: > 0.45 V). The ECM judges by the electromotive force from the oxygen sensor whether the air–fuel
ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the oxygen sen-
sor causes output of abnormal electromotive force, the ECM is unable to perform accurate air–fuel ratio con-
trol.
The heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by
the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the
heater to heat the sensor for accurate oxygen concentration detection.
Cover
P21242 FI7210
DTC No.
After engine is warmed up, heated oxygen sensor (bank 1, 2
sensor 1) output does not indicate RICH (u 0.45 V ) even
once when conditions (a), (b), (c) and (d) continue for at least
2 min.:
(a) Engine speed: 1,500 rpm or more
P0125
(b) Vehicle speed: 40 X SPD and 100 km/h (25 X SPD and
62 mph)
(c) Throttle valve does not fully closed
(d) 140 sec. or more after starting engine
DIAGNOSTICS
Insufficient Coolant Temp. for Closed Loop
Fuel Control (Except California Spec.)
Atmosphere
Exhaust Gas
DTC Detecting Condition
– ENGINE (1MZ–FE)
Flange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platium Electrode
Heater
Coating(Ceramic)
D Fuel system
D Injector
D Ignition system
D Gas leakage on exhaust system
D Open or short in heated oxygen sensors (bank 1, 2 sensor 1)
circuit
D Heated oxygen sensors (bank 1, 2 sensor 1)
D ECM
Author :
Ideal Air–Fuel Mixture
Air Fuel Ratio
Richer
Trouble Area
Date :
DI07M–08
Leaner
A00027
479