Engine General Information and Diagnosis: 1A-78
DTC Troubleshooting
NOTE
Before this trouble shooting is performed, read the precautions for DTC troubleshooting referring to
“Precautions For DTC Troubleshooting: ”.
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
MAF sensor and its circuit check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Start engine and check MAF value displayed on scan
tool. (Refer to “Scan Tool Data: ” for normal value.)
Is normal value indicated?
Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection: in Section
00”.
Go to Step 3.
3
MAF sensor power supply voltage check
1) Disconnect connector from MAF and IAT sensor with
ignition switch tuned OFF.
2) Turn ON ignition switch, measure voltage between
engine ground and “BLU/BLK” wire terminal of MAF and
IAT sensor connector.
Is voltage 10 – 14 V?
Go to Step 4.
“BLU/BLK” wire is open
circuit.
4
MAF sensor ground circuit check
1) Turn OFF ignition switch, measure resistance between
“BLU” wire terminal of MAF and IAT sensor connector
and engine ground.
Is resistance below 5
Ω
?
Go to Step 6.
Go to Step 5.
5
Ground circuit check
1) Remove ECM from its bracket with ECM connectors
connected.
2) Measure resistance between “C37-27” terminal of ECM
connector and engine ground.
Is resistance below 5
Ω
?
“BLU” wire is open or
high resistance circuit.
ECM grounds “C37-58”,
“C37-48”, “C37-30”,
“C37-29” and/or “C37-
15” circuit are open or
high resistance.
If wires are OK,
substitute a known-
good ECM and recheck.
6
MAF sensor signal circuit check
1) Disconnect connectors from ECM with ignition switch
turned OFF.
2) Measure voltage between “RED” wire terminal of MAF
and IAT sensor connector and engine ground.
Is voltage 0 V?
Go to Step 7.
“RED” wire is shorted to
other circuit.
7
MAF sensor output signal check
1) Connect connector to MAF and IAT sensor and ECM
with ignition switch turned OFF.
2) Measure voltage between “C37-26” and “C37-27”
terminal of ECM connector referring to “Mass Air Flow
(MAF) and Intake Air Temperature (IAT) Sensor On-
Vehicle Inspection: in Section 1C”.
Is each value within specified range?
Substitute a known-
good ECM and recheck.
Faulty MAF and IAT
sensor.
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