6-10 ENGINE GENERAL INFORMATION AND DIAGNOSIS
ON-BOARD DIAGNOSTIC SYSTEM (VEHICLE
WITHOUT IMMOBILIZER INDICATOR LAMP)
ECM diagnosis troubles which may occur in the area including
the following parts when the ignition switch is ON and the engine
is running, and indicates the result by turning on or flashing mal-
function indicator lamp (1).
Heated oxygen sensor (if equipped)
ECT sensor
TP sensor
IAT sensor
MAP sensor
CMP sensor
CKP sensor
Knock sensor (if equipped)
VSS
CPU (Central Processing Unit) of ECM
ECM and malfunction indicator lamp (1) operate as follows.
Malfunction indicator lamp (1) lights when the ignition switch
is turned ON (but the engine at stop) with the diagnosis
switch terminal ungrounded regardless of the condition of
Engine and Emission control system. This is only to check
the malfunction indicator lamp (1) bulb and its circuit.
If the above areas of Engine and Emission control system
are free from any trouble after the engine start (while engine
is running), malfunction indicator lamp (1) turns OFF.
When ECM detects a trouble which has occurred in the
above areas, it makes malfunction indicator lamp (1) turn ON
while the engine is running to warn the driver of such occur-
rence of trouble and at the same time it stores the trouble
area in ECM back-up memory. (The memory is kept as it is
even if the trouble was only temporary and disappeared
immediately. And it is not erased unless the power to ECM is
shut off for specified time below.)
ECM also indicates trouble area in memory by means of
flashing of malfunction indicator lamp (1) at the time of
inspection. (i.e. when diagnosis switch terminal (2) is con-
nected to ground terminal (3) with a service wire and ignition
switch is turned ON.)
NOTE:
When a trouble occurs in the above areas and disap-
pears soon while the diagnosis switch terminal is
ungrounded and the engine is running, malfunction
indicator lamp (1) lights and remains ON as long as the
trouble exists but it turns OFF when the normal condi-
tion is restored.
Time required to erase diagnostic trouble code mem-
ory thoroughly varies depending on ambient tempera-
ture as follows.
ODO TRIP AB
1
32
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-47
TABLE A-2 MALFUNCTION INDICATOR LAMP CIRCUIT CHECK - LAMP
REMAINS “ON” AFTER ENGINE STARTS
WIRING DIAGRAM / CIRCUIT DESCRIPTION
Refer to table A-1.
INSPECTION
3 MIL Circuit Check
1) Turn ignition switch OFF and disconnect
connectors from ECM.
2) Check for proper connection to ECM at ter-
minal G02-1 (Case of TYPE A. See NOTE)
or G02-9 (Case of TYPE B. See NOTE).
3) If OK, then using service wire, ground termi-
nal G02-1 (Case of TYPE A. See NOTE) or
G02-9 (Case of TYPE B. See NOTE) in con-
nector disconnected.
Does MIL turn on at ignition switch ON?Substitute a known-good
ECM and recheck.Bulb burned out or “PPL/
YEL” (Case of TYPE A.
See NOTE) or “PPL/
WHT” (Case of TYPE B.
See NOTE) wire circuit
open.
Test switch terminal cir-
cuit grounded (vehicle
without immobilizer indi-
cator lamp) Step Action Yes No
NOTE:
For TYPE A and TYPE B, refer to NOTE in “ECM VOLTAGE VALUES TABLE” for applicable model.
Step Action Yes No
1 Diagnostic Trouble Code (DTC) Check
1) Check DTC referring to DTC CHECK
section.
Is there any DTC(s)?Go to Step 2 of ENGINE DIAG.
FLOW TABLE.Go to Step 2.
2DTC Check
1) Start engine and recheck DTC while
engine running.
Is there any DTC(s)?Go to Step 3.
3 MIL Circuit Check
1) Turn OFF ignition switch.
2) Disconnect connectors from ECM.
Does MIL turn ON at ignition switch ON?“PPL/YEL” (Case of TYPE A.
See NOTE) or “PPL/WHT”
(Case of TYPE B. See NOTE)
wire circuit shorted to ground.Substitute a known-good
ECM and recheck.
