Engine General Information and Diagnosis: 1A-73
Step Action Yes No
1 Was “Engine and Emission Control System Check”
performed?
Go to Step 2. Go to “Engine and
Emission Control
System Check”.
2 IAT sensor and its circuit check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Turn ON ignition switch.
3) Check intake air temp. displayed on scan tool.
Is 119
°
C (246
°
F) indicated?
Go to Step 3. Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection in Section
00”.
3 ECM voltage check
1) Disconnect connector from MAF and IAT sensor with
ignition switch turned OFF.
2) Check for proper connection to MAF and IAT sensor at
“BLK/YEL” and “GRY/BLU” wire terminals.
3) If OK, then turn ON ignition switch, measure voltage
between “BLK/YEL” wire terminal of MAF and IAT
sensor connector (1) and vehicle body ground.
Is voltage about 4 – 6 V?
Go to Step 6. Go to Step 4.
4 IAT short circuit check
1) Disconnect connectors from ECM with ignition switch
turned OFF.
2) Measure resistance between “BLK/YEL” wire terminal of
MAF and IAT sensor connector and vehicle body
ground.
Is resistance infinity?
Go to Step 5. “BLK/YEL” wire is
shorted to ground
circuit.
If wire is OK, substitute
a known-good ECM and
recheck.
5 IAT short circuit check
1) Turn ON ignition switch.
2) Measure voltage between “BLK/YEL” wire terminal of
MAF and IAT sensor connector and vehicle body
ground.
Is voltage about 0 V?
Go to Step 6. “BLK/YEL” wire is
shorted to other circuit.
If wire is OK, substitute
a known-good ECM and
recheck.
6 IAT sensor for performance check
1) Check IAT sensor according to “MAF and IAT Sensor
Inspection in Section 1C”.
Is it in good condition?
Substitute a known-
good ECM and recheck.
Replace MAF and IAT
sensor.
I4RS0B110020-01
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