Electronic Circuit Inspection Procedure

1. Unless stated, all resistance measurements should be made at an ambient temperature of 20°C (68°F). Resistance measurements may be outside the specifications if measured at high temperatures, i.e. immediately after the vehicle has been running. Measurements should be made after the engine has cooled down.
   Fig 1: Precaution For Handling Connectors

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

1. When disconnecting a connector, first squeeze the mating halves tightly together to release the lock, then press the lock claw and separate the connector.
2. When disconnecting a connector, do not pull on the harnesses. Grasp the connector directly and separate it.
3. Before connecting a connector, check that there are no deformed, damaged, loose or missing terminals.
4. When connecting a connector, press firmly until you hear the lock close with a "click" sound.
5. If checking a connector with a TOYOTA electrical tester, check the connector from the backside (harness side) using a mini test lead.

1. Checking when a connector is connected:

   Squeeze the connector together to confirm that it is fully connected and locked.

   Fig 2: Identifying Core Wire

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
2. Checking when a connector is disconnected:

   Check by pulling the wire harness lightly from the backside of the connector. Look for unlatched terminals, missing terminals, loose crimps or broken conductor wires.

   Check visually for corrosion, metallic or foreign objects and water; and bent, rusted, overheated, contaminated, and deformed terminals.

   NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal.
   Fig 3: Checking Contact Pressure Of Terminal

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
3. Checking the contact pressure of the terminal:

   Prepare a spare male terminal. Insert it into a female terminal, and check for ample tension when inserting and after full engagement.

   Fig 4: Precaution For Repair Method Of Connector Terminal

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

1. If there is any dirt on the terminal, clean the contact point using an air gun or cloth. Never rub the contact point using sandpaper as the plating may come off.
2. If there is abnormal contact pressure, replace the female terminal. If the male terminal is gold-plated (gold color), use a gold-plated female terminal; if it is silver-plated (silver color), use a silver-plated female terminal.
3. Damaged, deformed, or corroded terminals should be replaced. If the terminal will not lock into the housing, the housing may have to be replaced.

Fig 5: Precaution For Handling Of Wire Harness

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

1. If removing a wire harness, check the wiring and clamping before proceeding so that it can be restored in the same way.
2. Never twist, pull or slacken the wire harness more than necessary.
3. The wire harness should never come into contact with a high temperature part, or rotating, moving, vibrating or sharp-edged parts. Avoid contact with panel edges, screw tips and other sharp items.
4. When installing parts, never pinch the wire harness.
5. Never cut or break the cover of the wire harness. If it is cut or broken, replace it or securely repair it with vinyl tape.

Fig 6: Checking Open Circuit

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Fig 7: Checking Resistance

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

1. Disconnect connectors A and C and measure the resistance between them.
   TESTER CONNECTION SPECIFIED CONDITION
   
   

   Tester Connection	Specified Condition
   Connector A terminal 1 - Connector C terminal 1	10 kΩ or higher
   Connector A terminal 2 - Connector C terminal 2	Below 1 Ω

   HINT:

   Measure the resistance while lightly shaking the wire harness vertically and horizontally.

   If your results match the examples above, an open circuit exists between terminal 1 of connector A and terminal 1 of connector C.

   Fig 8: Measuring Resistance Between Connectors

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
2. Disconnect connector B and measure the resistance between the connectors.

If your results match the examples above, an open circuit exists between terminal 1 of connector B2 and terminal 1 of connector C.

Fig 9: Checking Voltage

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

1. In a circuit in which voltage is applied to the ECU connector terminal, an open circuit can be checked by conducting a voltage check.

Fig 9:

With each connector still connected, measure the voltage between the body ground and these terminals (in this order): 1) terminal 1 of connector A, 2) terminal 1 of connector B, and 3) terminal 1 of connector C.

If your results match the examples above, an open circuit exists in the wire harness between terminal 1 of connector B and terminal 1 of connector C.

1. Disconnect connectors A and C and measure the resistance.
   TESTER CONNECTION SPECIFIED CONDITION
   
   

   Tester Connection	Specified Condition
   Connector A terminal 1 - Body ground	Below 1 Ω
   Connector A terminal 2 - Body ground	10 kΩ or higher

   HINT:

   Measure the resistance while lightly shaking the wire harness vertically and horizontally.

   If your results match the examples above, a short circuit exists between terminal 1 of connector A and terminal 1 of connector C.

   Fig 12: Measuring Resistance

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
2. Disconnect connector B and measure the resistance.

If your results match the examples above, a short circuit exists between terminal 1 of connector B2 and terminal 1 of connector C.

1. Measure the resistance between the ECU ground terminal and body ground.
   Fig 13: Measuring Resistance Between ECU Ground Terminal And Body Ground

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

   Standard: Below 1 Ω 

   Fig 14: Disconnecting ECU Connector

   Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
2. Disconnect the ECU connector. Check the ground terminals (on the ECU side and wire harness side) for evidence of bending, corrosion or foreign material. Lastly, check the contact pressure of the female terminals.