IN−36 − INTRODUCTION HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS Fig. 4 (b) Check the voltage. In a circuit in which voltage is applied (to the ECU connec- tor terminal), an open circuit can be checked for by con- ducting a voltage check. As shown in Fig. 4, with each connector still con- nected, measure the voltage between body ground and terminal 1 of connector ”A” at the ECU 5V out- put terminal, terminal 1 of connector ”B”, and termi- nal 1 of connector ”C”, in that order. If the results are: 5V: Between Terminal 1 of connector ”A” and Body Ground 5V: Between Terminal 1 of connector ”B” and Body Ground 0V:
Between Terminal 1 of connector ”C” and Body Ground Then it is found out that there is an open circuit in the wire har- ness between terminal 1 of ”B” and terminal 1 of ”C”. 0V 5V Sensor 2 1 A C 1 1 2 2 5V B 5V Z17007 7. CHECK SHORT CIRCUIT If the wire harness is ground shorted as in Fig. 5, locate the sec- tion by conducting a ”continuity check with ground”. Fig. 5 2 1 A C 1 1 2 2 B SHORT Z17008 Fig. 6 Check the continuity with ground. (1) Disconnect connectors ”A” and ”C” and measure the resistance between terminal 1 and 2 of connec- tor ”A” and body ground. In the case of Fig.
6 Between terminal 1 of connector ”A” and body ground → Continuity (short) Between terminal 2 of connector ”A” and body ground → No continuity Therefore, it is found out that there is a short circuit between terminal 1 of connector ”A” and terminal 1 of connector ”C”. B Sensor 2 1 A C 1 1 2 2 ECU Z17009 36 Author : Date: