Electronic Circuit Inspection Procedure

BASIC INSPECTION
1. RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS
  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.
2. HANDLING CONNECTORS
  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 the 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 the connector with a TOYOTA electrical tester, check the connector from the backside (harness side) using a mini test lead.
  NOTE:
  - As a waterproof connector cannot be checked from the backside, check by connecting a sub-harness.
  - Do not damage the terminals by moving the inserted tester needle.
3. CHECKING CONNECTORS
  1. Checking when a connector is connected: Squeeze the connector together to confirm that it is fully connected and locked.
  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.
    
    Fig 1: Identifying Proper Way Of Connecting And Disconnecting Connectors
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    
    Fig 2: Checking Connectors
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    
    NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal.
  3. Checking the contact pressure of the terminal: Prepare a spare male terminal. Insert it into a female terminal, and check for good tension when inserting and after full engagement.
  Fig 3: Checking Contact Pressure Of Connector Terminal
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. REPAIR METHOD FOR CONNECTOR TERMINAL
  1. If there is any dirt on the terminal, clean the contact point using an air gun or cloth. Never polish the contact point using sandpaper as the platings 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 4: Identifying Proper Method Of Repairing Connector Terminal
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
5. HANDLING OF WIRE HARNESS
  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 high temperature part, or rotating, moving, vibrating or sharp-edged parts. Avoid panel edges, screw tips and similar 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 5: Identifying Proper Way Of Handling Wire Harness
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

CHECK OPEN CIRCUIT

For an open circuit in the wire harness in Figure, perform a resistance check (step b) or a voltage check (step c).

Fig 6: Checking Open Circuit
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Check the resistance.

Disconnect connectors A and C and measure the resistance between them.

TESTER CONNECTION AND RESISTANCE SPECIFICATIONS (1 OF 5)

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

Fig 7: Measuring Circuit Resistance (1 Of 2)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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.

Disconnect connector B and measure the resistance between the connectors.

Figure

TESTER CONNECTION AND RESISTANCE SPECIFICATIONS (2 OF 5)

Tester Connection	Specified Condition
Connector A terminal 1- Connector B1 terminal 1	Below 1 Ω
Connector B2 terminal 1- Connector C terminal 1	10 kΩ or higher

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

Fig 8: Measuring Circuit Resistance (2 Of 2)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Check the voltage.

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

With each connector still connected, measure the voltage between the body ground and these terminals (in this order): 1) terminal 1 of connector A at the ECU 5 V output terminal, 2) terminal 1 of connector B, and 3) terminal 1 of connector C.

Example results:

TESTER CONNECTION AND VOLTAGE SPECIFICATIONS (3 OF 5)

Tester Connection	Specified Condition
Connector A terminal 1- Body ground	5V
Connector B terminal 1- Body ground	5V
Connector C terminal 1- Body ground	0V

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.

Fig 9: Measuring Circuit Voltage

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

CHECK SHORT CIRCUIT

If the wire harness is ground shorted (Figure ), locate the section by conducting a resistance check with the body ground (below).

Fig 10: Checking Short Circuit (1 Of 2)
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Check the resistance with the body ground.

Disconnect connectors A and C and measure the resistance between terminals 1 and 2 of connector A and the body ground.

Figure

TESTER CONNECTION AND RESISTANCE SPECIFICATIONS (4 OF 5)

Tester Connection	Specified Condition
Connector A terminal 1- Body ground	Below 1 Ω
Connector A terminal 2- Connector C terminal 2	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 11: Checking Short Circuit (2 Of 2)

Disconnect connector B and measure the resistance between terminal 1 of connector A and the body ground, and terminal 1 of connector B2 and the body ground.

Figure

TESTER CONNECTION AND RESISTANCE SPECIFICATIONS (5 OF 5)

Tester Connection	Specified Condition
Connector A terminal 1- Body ground	10 kΩ or higher
Connector B2 terminal 1- Body ground	Below 1 Ω

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

Fig 12: Measuring Resistance Between Terminal And Body Ground

CHECK AND REPLACE ECU
NOTE:
- The connector should not be disconnected from the ECU. Perform the inspection from the backside of the connector on the wire harness side.
- When no measuring condition is specified, perform the inspection with the engine stopped and the ignition switch ON.
- Check that the connectors are fully seated. Check for loose, corroded or broken wires.
1. First, check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. Replace the ECU with a functioning one and check if the symptoms occur. If the trouble symptoms stop, replace the ECU.
1. Measure the resistance between the ECU ground terminal and body ground.
  Standard: Below 1 Ω
  
  Fig 13: Measuring Resistance Between ECU Ground Terminal And Body Ground
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 14: Disconnecting ECU Connector And Checking Ground Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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.