Honda BF135A - Iat Sensor Troubleshooting

BF135A•BF150A
5-38
• IAT Sensor Troubleshooting
DTC 10-1: IAT sensor voltage is low
1. Symptom reproduction test
-1. Connect the HDS pocket tester and clear the DTC
once. If the DTC can not be cleared, go on the trou-
bleshooting.
-2. Turn the ignition switch ON.
-3. Measure the IAT sensor (TA) voltage using the HDS
pocket tester.
Is the measurement voltage 0.08 – 4.92V?
YES – Temporary failure (Disappeared)
NO – Perform “2. IAT sensor line short circuit
check”.
2. IAT sensor line short circuit check
-1. Turn the ignition switch OFF and disconnect the ECM
connector B.
-2. Check for the continuity between the No. 2
(Red/Yellow) terminal of the IAT sensor harness side
2P connector and the body ground.
Is there the continuity?
YES – Repair short in the wire between the ECM
and the IAT sensor.
NO – Perform “3. IAT sensor check”.
3. IAT sensor check
-1. Turn the ignition switch OFF and connect the HDS
pocket tester.
-2. Turn the ignition switch ON and check the intake air
temperature using the HDS pocket tester.
Does the measurement correspond to the ambient
temperature?
YES – Substitute a known-good ECM and recheck.
NO – Replace the IAT sensor with a new one and
recheck.
DTC 10-2: IAT sensor voltage is high
1. Symptom reproduction test
-1. Connect the HDS pocket tester and clear the DTC
once. If the DTC can not be cleared, go on the trou-
bleshooting.
-2. Turn the ignition switch ON.
-3. Measure the IAT sensor (TA) voltage using the HDS
pocket tester.
Is the measured voltage 0.08 – 4.92V?
YES – Temporary failure (Disappeared)
NO – Perform “2. IAT sensor signal line open circuit
check”.
2. IAT sensor signal line open circuit check
-1. Turn the ignition switch OFF and disconnect the IAT
sensor 2P connector.
-2. Turn the ignition switch ON. Measure the voltage
between the No. 2 (Red/Yellow) terminal of the IAT
sensor harness side 2P connector and the engine
ground.
Is the measured voltage 4.75 – 5.25V?
YES – Perform “3. IAT sensor ground line open cir-
cuit check”.
NO – Repair open in the wire between the IAT sen-
sor and the ECM.
3. IAT sensor ground line open circuit check
-1. Turn the ignition switch OFF.
-2. Check for the continuity between the No. 1
(Green/Red) terminal of the IAT sensor harness side
2P connector and the body ground.
IAT SENSOR HARNESS
SIDE 2P CONNECTOR
TA (RED/YELLOW)
VIEWED FROM THE
TERMINAL SIDE
IAT SENSOR HARNESS
SIDE 2P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
IAT SENSOR HARNESS
SIDE 2P CONNECTOR
SG2 (GREEN/RED)
VIEWED FROM THE
TERMINAL SIDE
TA (RED/YELLOW)