General Precautions of EFI System Maintenance
F-31
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
P0138
P0138
Maintenance tips:
The malfunction has been confirmed, and the
following problems may possibly exist
1) The circuit connected to the Pin 55# of ECU and
the Pin C# of oxygen sensor in short circuit
2) The circuit connected to the Pin 55# 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) Measure the eclectic resistance for the Pin 55#
of ECU to the Pin C# of oxygen sensor.
3) Measure the voltage for the Pin 55# of ECU.
35. P0140 Downstream Oxygen Sensor Circuit Signal Malfunction
Description about Malfunction Cause:
After engine has been started, ECU will perform measurement on circuit voltage of downstream oxygen
sensor, and the system will determine it to be the signal of downstream oxygen sensor in open circuit, if signal
voltage always maintains a certain value between 0.4~0.6V without change. Schematic Circuit:
Malfunction Diagnostic Guide:
Required Equipment: (Diagnostic Instrument with EOBD Diagnostic Function, Digital Multimeter, and
Correct Circuit Diagram)
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
P0140
P0140
Maintenance tips:
The malfunction has been confirmed, and the
following problems may possibly exist
1) The circuit of oxygen sensor connected to
the Pin 55# of ECU in open circuit
2) The connector of oxygen sensor in bad
contact (pin oxidized)
Maintenance tips:
The malfunction is not ultimately confirmed and it may
possibly be a random malfunction. Inspect the following
items:
1) Measure the electric resistance of the Pin 55# for
connector of ECU to the Pin B# of oxygen sensor
Mian relay
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