Ect Sensor 4 Troubleshooting - Honda BF135A Manual

5. EOP switch check
-1. Turn the ignition switch OFF and connect all the con-
nectors.
-2. Turn the ignition switch ON and check the EOP switch
using the HDS pocket tester.
Does the tester shows the switch OFF?
YES – If the DTC appears again, substitute a known-
good ECM and recheck.
NO – Replace the EOP switch.
5-55

• ECT Sensor 4 Troubleshooting

DTC 143-1: ECT sensor 4 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 ECT sensor 4 voltage using the HDS
pocket tester.
Is the measured voltage 0.08 – 4.99V?
YES – Temporary failure (Disappeared)
NO – Perform "2. ECT sensor 4 signal line short cir-
cuit check".
2. ECT sensor 4 signal line short circuit check
-1. Turn the ignition switch OFF. Disconnect the ECT sen-
sor 4 connector and the ECM connector B.
-2. Check for the continuity between the No. 2
(Red/Green) terminal of the ECT sensor 4 harness
side connector and the body ground.
ECT SENSOR 4 HARNESS
SIDE 2P CONNECTOR
VIEWED FROM THE
TERMINAL SIDE
Is there the continuity?
YES – Repair short in the wire between the ECT
sensor 4 and the ECM.
NO – Perform "3. ECT sensor 4 check".
3. ECT sensor 4 check
-1. Turn the ignition switch OFF and connect the ECT sen-
sor 4 2P connector.
-2. Turn the ignition switch ON. Measure the ECT sensor
4 temperature using the HDS pocket tester.
Does the measurement correspond to the engine
coolant temperature?
YES – If the DTC appears again, substitute a known-
good ECM and recheck.
NO – Replace the ECT sensor 4.
BF135A•BF150A
TOH3
(RED/GREEN)