Toyota Celica 2005, Repair Manual

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A20806
Rich
Lean
0.45
Oxygen
sensor output voltage (V)
0.55
FAIL
FAIL
Pass / Fail definition of voltage malfunction
Time
PASS
FAIL
0.40
− DIAGNOSTICS ENGINE (1ZZ − FE)
DI − 113
2005 CELICA (RM1131U)
MONITOR DESCRIPTION
The ECM uses the heated oxygen sensor information to regulate the air − fuel ratio to be close to a stoichio-
metric ratio. This maximizes the catalytic converter’s ability to purify the exhaust gas. The sensor detects
oxygen level in the exhaust gas and sends this signal to the ECM.
The inner surface of the sensor element is exposed to outside air. The outer surface of the sensor element
is exposed to exhaust gas. The sensor element is made of platinum coated zirconia and includes an inte-
grated heating element. The heated oxygen sensor has the characteristic whereby its output voltage
changes suddenly in the vicinity of the stoichiometric air
− fuel ratio. The heated oxygen sensor generates
output voltage between 0 V and 1.0 V in response to the oxygen concentration in exhaust gas. When the
output voltage of the heated oxygen sensor is 0.55 V or more, the ECM judges that the air
− fuel ratio is RICH.
When it is 0.4 V or less, the ECM judges that the air − fuel ratio is LEAN.
Under normal condition, the output voltage from the heated oxygen sensor alternates RICH and LEAN sides
periodically. If the heated oxygen sensor outputs RICH signal (or LEAN signal) constantly, or if the heated
oxygen sensor cannot output enough voltage to reach the minimum specification, the ECM interprets this
as a malfunction in the heated oxygen sensor and sets a DTC.
MONITOR STRATEGY
Related DTCs P0130
Front heated oxygen sensor voltage is constant
at lean side or rich side
Required sensors/components
Main sensors/components Front heated oxygen senor
Related sensors/components Crank position sensor, Vehicle speed sensor
Frequency of operation Once per driving cycle
Duration 20 to 36 sec. x (3 times)
MIL operation 2 driving cycles
Sequence of operation None
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