Engine General Information and Diagnosis: 1A-86
5 Wire circuit check
1) Disconnect connectors from ECM with ignition switch
turned OFF.
2) Measure resistance between “LT GRN” wire terminal of
MAF and IAT sensor connector and vehicle body
ground.
Is resistance infinity?
Go to Step 6. “LT GRN” wire is
shorted to ground or
other circuit.
If wire is OK, substitute
a known-good ECM and
recheck.
6 Wire circuit check
1) Turn ignition switch to ON position.
2) Measure voltage between “LT GRN” wire terminal of
MAF and IAT sensor connector and vehicle body
ground.
Is voltage about 0 V?
Go to Step 7. “LT GRN” wire shorted
to other circuit.
If wire is OK, substitute
a known-good ECM and
recheck.
7 Wire circuit check
1) Measure resistance between “C37-25” terminal of ECM
connector and “LT GRN” wire terminal of MAF and IAT
sensor connector with ignition switch turned OFF.
Is resistance below 3
Ω
?
Go to Step 8. “LT GRN” wire is high
resistance circuit.
8 Ground circuit check
1) Connect connectors to ECM.
2) Check for proper connection of MAF and IAT sensor
connector at “GRY/GRN” wire terminal.
3) Measure resistance between “GRY/GRN” wire terminal
of MAF and IAT sensor connector and vehicle body
ground with ignition switch turned OFF.
Is resistance below 5
Ω
?
Go to Step 10. Go to Step 9.
9 Ground circuit check
1) Remove ECM from its bracket with ECM connectors
connected.
2) Measure resistance between “C37-57” terminal of ECM
connector and vehicle body ground.
Is resistance below 3
Ω
?
“GRY/GRN” wire is
open or high resistance
circuit.
Poor “C37-57”
connection.
Faulty ECM ground
circuit.
If circuit is OK,
substitute a known-
good ECM and recheck.
10 IAT sensor check
1) Check IAT sensor according to “Mass Air Flow (MAF)
and Intake Air Temperature (IAT) Sensor Inspection: in
Section 1C”.
Is it in good condition?
Substitute a known-
good ECM and recheck.
Replace MAF and IAT
sensor.
Step Action Yes No
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