Toyota Camry Manual page 1082

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 A/F sensor has the characteristic that provides output voltage
ing air–fuel ratio. The A/F sensor output voltage
fuel ratio.
By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air–fuel ratio
and control the proper injection time immediately. If the A/F sensor is malfunctioning, ECM is unable to per-
form accurate air–fuel ratio control.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the
ECM. When the intake air volume is low (the temp. of the exhaust gas is low), current flows to the heater
to heat the sensor for accurate oxygen concentration detection.
*: The voltage value changes at the inside of the ECM only.
Cover
DTC No.
After engine is warmed up, A/F sensor output* does not
change when conditions (a), (b), and (c) continue for at least
1.5 min.:
P0125 *: Output value changes at inside of ECM only
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 ∼ 100 km/h (25 ∼ 62 mph)
(c) Throttle valve is not fully closed
DIAGNOSTICS
Insufficient Coolant Temp. for Closed Loop
Fuel Control (Only for California Spec.)
*
Atmosphere
Solid Electrolyte
(Zirconia Element)
Platinum
Electrode
Heater
Coating (Ceramic)
Exhaust Gas
DTC Detecting Condition
– ENGINE (5S–FE)
approximately proportional to the exist-
*
is used to provide feedback for the ECM to control the air–
(V)
Platinum
4.0
Electrode
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
D Fuel system
D Injector
D Ignition system
D Gas leakage on exhaust system
D Open or short in A/F sensor circuit
D A/F sensor
D ECM
Author :
12 13 14 15 16 17 18
Air–Fuel Ratio
Trouble Area
Date :
DI–55
DI1JU–03
19
A00477
290