Monitor description
The ecm uses sensors mounted in front of and behind the three-way catalytic converter (twc) to monitor its efficiency.
The first sensor, the air-fuel ratio (a/f) sensor, sends pre-catalyst information to the ecm. The second sensor, the heated oxygen (ho2) sensor, sends post-catalyst information to the ecm.
In order to detect any deterioration in the twc, the ecm calculates the oxygen storage capacity (osc) of the twc. This calculation is based on the voltage output of the ho2 sensor while performing active airfuel ratio control, rather than the conventional detecting method, which uses the locus ratio.
The osc value is an indication of the oxygen storage capacity of the twc. When the vehicle is being driven with a warm engine, active air-fuel ratio control is performed for approximately 15 to 20 seconds.
When it is performed, the ecm deliberately sets the air-fuel ratio to lean or rich levels. If the rich-lean cycle of the ho2 sensor is long, the osc becomes greater. There is a direct correlation between the oscs of the ho2 sensor and the twc.
The ecm uses the osc value to determine the state of the twc. If any deterioration has occurred, it illuminates the mil and sets the dtc.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Monitor result
Refer to checking monitor status (see page es-17).
Confirmation driving pattern
Hint:
Performing this confirmation pattern will activate the catalyst monitor. This is very useful for verifying the completion of a repair.
Hint:
If cat cmpl does not change to compl, and any pending dtcs fail to set, extend the driving time.
Conditioning for sensor testing
Hint:
Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the a/f and ho2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.
Hint:
Inspection procedure
Hint:
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
Hint:
If any dtcs other than p0420 are output, troubleshoot those dtcs first.
Result: a/f sensor reacts in accordance with increases and decreases in fuel injection volume: +25 % = rich output: less than 3.0 V
-12.5 % = Lean output: more than 3.35 V
Notice:
The a/f sensor has an output delay of a few seconds and the ho2 sensor has a maximum output delay of approximately 20 seconds.
Following the a/f control procedure enables technicians to check and graph the voltage outputs of both the a/f and ho2 sensors.
To display the graph, select the following menu items on the tester: diagnosis / enhanced obd ii / active test / a/f control / user data / afs b1 s1 and o2s b1 s2; then press the yes button and then the enter button followed by the f4 button.
Ok: no gas leakage.
Replace three-way catalytic converter (both front and rear catalysts (front exhaust pipe))
Ok: no gas leakage.
Replacement
Replace intake valve guide bush
Heat the cylinder head to 80 to 100°c (176 to
212°f).
Place the cylinder head on wooden blocks.
Using sst and a hammer, tap out the guide bush.
Sst 09201-10000 (09201-01050), 09950-70010
(09951-07100)
Heat the cylinder head to 80 to 10 ...
Tire pressure warning ecu
Components
Removal
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove glove compartment door
assembly (see page i ...
Warning lights
Warning lights inform the driver
of malfunctions in the indicated
vehicle's systems.
Brake system warning
light*1
Brake system warning
light*1
Brake system warning
light*1
Charging system warning
light (vehicles without
12.3-inch multi-information
display)*1
Charging system warning
light (vehic ...