MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.0L>
13B-203
.
CIRCUIT OPERATION
•
A voltage corresponding to the oxygen concen-
tration in the exhaust gas is sent to the ECM (ter-
minal 71) <M/T> or PCM (terminal 71) <A/T>
from the output terminal (terminal 4) of the left
bank heated oxygen sensor (front).
•
Terminal 2 of the left bank heated oxygen sensor
(front) is grounded with ECM (terminal 49) <M/T>
or PCM (terminal 57) <A/T>.
.
TECHNICAL DESCRIPTION
•
The left bank heated oxygen sensor (front)
detects the concentration of oxygen in the
exhaust gas; it converts that data to voltage, and
sends it to the ECM <M/T> or PCM <A/T>.
•
When the left bank heated oxygen sensor (front)
begins to deteriorate, the heated oxygen sensor
signal response deteriorates also.
•
The ECM <M/T> or PCM <A/T> varies the air/fuel
mixture to make it leaner and richer, and checks
the response speed of the left bank heated oxy-
gen sensor (front). In addition, the ECM <M/T> or
PCM <A/T> also checks for an open circuit in the
left bank heated oxygen sensor (front) output
line.
.
DTC SET CONDITIONS
Check Conditions
•
Engine coolant temperature is higher than 50
°
C
(122
°
F).
•
Engine speed is at between 1,250 and 3,000 r/
min.
•
Volumetric efficiency is at between 20 and 60
percent.
•
Under the closed loop air/fuel control.
•
The throttle valve is open.
•
Short-term fuel trim is higher than
−
30 and lower
than +25 percent.
•
More than 3 seconds have elapsed after the
abovementioned conditions have been met.
•
The ECM <M/T> or PCM <A/T> monitors for this
condition for 7 cycles of 12 second each during
the drive cycle.
Judgment Criteria
•
The left bank heated oxygen sensor (front) sends
"lean" and "rich" signals alternately 11 times or
less for 12 seconds.
NOTE: If the sensor switch time is longer than the
Judgment Criteria due to the MUT-II OBD-II test
Mode
−
H02S Test Results, it is assumed that the
heated oxygen sensor has deteriorated. If it is
short, it is assumed that the harness wire is bro-
ken or has a short circuit.
If the heated oxygen sensor signal voltage has
not changed even once (lean/rich) after the DTC
was erased, the sensor switch time will display as
0 seconds.
.
ACX02489
AI
LEFT BANK
HEATED OXYGEN
SENSOR (FRONT)
AK103509AB
CONNECTOR: B-24
AK000225
CONNECTORS : C-58, C-62<M/T>,
C-55, C-59<A/T>
C-55
C-58
PCM<A/T>
ECM<M/T>
AK
C-59
C-62