Fuel System (Dohc) Diagnostic Chart (Fault Tree) - Mitsubishi 1989-1993 GALANT Service Manual

ON-BOARD DIAGNOSTIC
The engine control module monitors the input/out-
put signals (some signals at all times and the others
under specified conditions) of the engine control
module.
When it is noticed that an irregularity has continued
for a specified time or longer from when the irregu-
lar signal is initially monitored, passing a certain
number, the engine control module judges that an
irregularity has occurred, memorizes the diagnostic
trouble code, and outputs the signal to the on-board
diagnostic output terminal.
There are 16 on-board diagnostic items, including
the normal state, and the diagnostic results can be
read out with a voltmeter or scan tool.
Moreover, since memorization of the diagnostic
trouble codes is backed up directly by the battery,
the diagnostic results are memorized even if the ig-
nition key is turned off. The diagnostic trouble
codes will, however, be erased when the battery
terminal or the engine control module connector is
DIAGNOSTIC CHART (FAULT TREE)
Diagnostic trouble code
Output signal pattern
L - J
12
13
FUEL SYSTEM <DOHC> - Troubleshooting
On-board
diagnostic
item
Engine
control
module
Heated
oxygen
sensor
Volume air
flow sensor
Intake air
temperature
sensor
TSB Revision
disconnected. In addition, beginning with the engine
control module of 1990 and later models, the diag-
nostic trouble code are erased by turning on the ig-
nition switch and sending the diagnostic trouble
code erase signal from the scan tool to the engine
control module.
Caution
If the sensor connector is disconnected with
the ignition switch turned on, the diagnostic
trouble code is memorized. In this case, send
the diagnostic trouble code erase signal from
the scan tool to the engine control module or
disconnect the battery terminal (-) for 10 sec-
onds or more, and the diagnosis memory will
be erased.
The 16 on-board diagnostic items are provided as
follows, and if plural items are activated, they are all
indicated sequentially from the smallest code num-
ber.
Check item (Remedy)
(Replace engine control module)
Harness and connector
l
Heated oxygen sensor
l
Fuel pressure
l
Injectors (Replace if defective.)
l
Intake air leaks
l
Harness and connector
l
(If harness and connector are
normal, replace volume air flow
sensor assembly.)
Harness and connector
l
intake air temperature sensor
l
Memory
Retained
Retained
Retained