MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.0L>
13B-185
.
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
•
3 minutes or more have passed since the starting
sequence was completed.
•
Left bank heated oxygen sensor (front) signal
voltage has continued to be 0.2 volt or lower.
•
Engine coolant temperature is higher than 76
°
C
(169
°
F).
•
Engine speed is higher than 1,200 r/min.
•
Volumetric efficiency is higher than 25 percent.
•
Monitoring time: 7 seconds.
Judgment Criteria
•
Input voltage supplied to the ECM <M/T> or PCM
<A/T> interface circuit is higher than 4.5 volts
when 5 volts is applied to the left bank heated
oxygen sensor (front) output line via a resistor.
•
The ECM <M/T> or PCM <A/T> monitors for this
condition once during the drive cycle.
.
TROUBLESHOOTING HINTS (The most likely
causes for this code to be set are: )
•
Left bank heated oxygen sensor (front) deterio-
rated.
•
Open circuit in left bank heated oxygen sensor
(front) output line.
•
Open circuit in left bank heated oxygen sensor
(front) ground line.
•
ECM failed. <M/T>
•
PCM failed. <A/T>
DIAGNOSIS
Required Special Tools:
•
MB991502: Scan Tool (MUT-II)
•
MD998464: Test Harness
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