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TROUBLESHOOTING
Step
1
Was "Engine and Emission Control System
Check" performed?
2
ECT sensor and its circuit check.
1) Connect scan tool with ignition switch
turned OFF.
2) Turn ignition switch ON.
3) Check engine coolant temp. displayed on
scan tool.
Is –40°C (–40°F) indicated?
3
Check ECT voltage.
1) Disconnect connector from ECT sensor with
ignition switch turned OFF.
2) Check for proper connection to ECT sensor
at "LT GRN" and "ORN" wire terminals.
3) If OK, then turn ON ignition switch, check
voltage between "LT GRN" wire terminal of
ECT sensor connector and vehicle body
ground. See Fig. 1.
Is voltage about 4 – 6 V?
4
Check ECM voltage.
1) Disconnect connectors from ECM with igni-
tion switch turned OFF.
2) Remove ECM from vehicle body and con-
nect connectors to ECM.
3) Check for proper connection of ECM con-
nector at "C63-16" terminals.
4) If OK, then turn ON ignition switch, check
voltage between "C63-16" wire terminal of
ECM connector and vehicle body ground.
Is voltage about 4 – 6 V?
5
Check ECT sensor harness voltage.
1) Disconnect connectors from ECM with igni-
tion switch turned OFF.
2) Turn ON ignition switch.
3) Check voltage between "LT GRN" wire ter-
minal of ECT sensor connector and vehicle
body ground.
Is voltage about 0 V?
6
Check ECT sensor harness resistance.
1) Measure resistance between "C63-16" ter-
minal of ECM connector and "LT GRN" wire
terminal of ECT sensor connector with igni-
tion switch turn OFF.
Is resistance below 5 Ω?
Action
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-83
Yes
Go to Step 2.
Go to Step 3.
Go to Step 6.
"LT GRN" wire open cir-
cuit.
If wire and connection are
OK, go to Step 5.
Go to Step 6.
Go to Step 7.
No
Go to "Engine and Emis-
sion Control System
Check" in this section.
Intermittent trouble.
Check for intermittent
referring to "Intermittent
and Poor Connection" in
Section 0A.
Go to Step 4.
Go to Step 5.
"LT GRN" wire shorted to
other circuits.
If wire are OK, substitute
a known-good ECM and
recheck.
"LT GRN" wire in high
resistance circuit.
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