General Precautions of EFI System Maintenance
F-57
Step I: Use diagnostic instrument to read the malfunction information
Read Result I Read Result II
MIL Lamp On P-CODE Present MIL Lamp Off P-CODE Present
P0368
P0368
Maintenance tips:
The malfunction has been confirmed, and the
following problems may possibly exist
1) The circuit connected to the Pin 72# of ECU and
the circuit for the Pin 3# of phase sensor in short
circuit
2) The circuit connected to the Pin 72# of ECU and
the other power supply circuit in short circuit
Maintenance tips:
The malfunction is not ultimately confirmed and it
may possibly be a random malfunction. Inspect the
following items:
1) Inspect the electric resistance of the circuit for
the Pin 72# of ECU to power supply.
2) Inspect the electric resistance of the circuit for
the Pin 72# of ECU and the circuit for the Pin 3#
of phase sensor.
72. P0420 Three-Way Catalyst Converter Oxygen Storage Capacity Aged (Emission over
Standard)
Description about Malfunction Cause:
Corresponding relationship exists between the transformation efficiency of the three-way catalyst converter
and its oxygen storage capacity, while the value of amplitude for the downstream oxygen sensor may
indirectly reflect the oxygen storage capacity of the catalyst. It indicates that the poorer the oxygen storage
capacity is, the larger value of amplitude the signal fluctuation of oxygen sensor is, and the poorer the
corresponding transformation capacity of the catalyst converter is. The main principle for diagnosis of the
catalyst converter is for the system to monitor the value of amplitude for voltage fluctuation of the
downstream oxygen sensor, and if the measured amplitude exceeds the set limit value, the system will
determine it to be the malfunction of the three-way catalyst converter.
Malfunction Symptom: Emission over Standard
Downstream Oxygen Sensor Signal (New Catalyst Converter)
Modular Sensor Signal (Borderline Catalyst Converter)
Downstream Oxygen Sensor Signal (Failed Catalyst Converter)
Modular Sensor Signal (Borderline Catalyst Converter)
Amplitude of
Vibration
Lower than Model
Amplitude of
Vibration
Amplitude of
Vibration
Higher than Model
Amplitude of
Vibration
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