FI SYSTEM AND INTAKE AIR SYSTEM 4-41
“C21” IAT SENSOR CIRCUIT MALFUNCTION
DETECTED CONDITION POSSIBLE CAUSE
High intake air temp. (Low voltage – Low • Dg circuit shorted to ground.
resistance) • B/Br circuit open.
Low intake air temp. (High voltage – High • IAT sensor malfunction.
resistance) • ECM malfunction.
INSPECTION
• Lift and support the fuel tank with its prop stay. ( 4-51)
Turn the ignition switch OFF.
Check the IAT sensor coupler for loose or poor contacts.
If OK, then measure the IAT sensor voltage at the wire
side coupler.
Disconnect the coupler and turn the ignition switch ON.
Measure the voltage between Dg wire terminal and
ground.
If OK, then measure the voltage between Dg wire termi-
nal and B/Br wire terminal.
IAT sensor voltage: 4.5 – 5.5 V
(
+Dg – -Ground
)
+Dg – -B/Br
09900-25008: Multi circuit tester
Tester knob indication: Voltage (
)
No Loose or poor contacts on
the ECM coupler.
Open or short circuit in the
Dg wire or B/Br wire.
Yes
Turn the ignition switch OFF.
Measure the IAT sensor resistance.
IAT sensor resistance: 2.2 – 2.7 k
ΩΩ
ΩΩ
Ω at 20°C (68°F)
(Terminal – Terminal)
09900-25008: Multi circuit tester
Tester knob indication: Resistance (
ΩΩ
ΩΩ
Ω)
No Replace the IAT sensor
with a new one.
Yes
Dg or B/Br wire open or shorted to ground, or poor j or n
connection. ( 4-25)
If wire and connection are OK, intermittent trouble or faulty ECM.
Recheck each terminal and wire harness for open circuit and
poor connection. ( 4-4)
Replace the ECM with a new one,
and inspect it again.
1
2
1
2
Intake Air Temp. Resistance
20°C( 68°F) Approx. 2.45 kΩ
50°C (122 °F) Approx. 0.808 kΩ
80°C (176 °F) Approx. 0.322 kΩ
110°C (230 °F) Approx. 0.148 kΩ
NOTE:
IAT sensor resistance measurement
method is the same way as that of the
ECT sensor. Refer to page 5-8 for details.
ECM couplers
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