A.D.D. Control System: Location: Inspection

Inspect Automatic Disconnecting Differential (A.D.D.) actuator
1. Disconnect the actuator connector.
2. Measure the resistance between the terminals 2 and 6.
  
  Fig 1: Identifying A.D.D. Actuator Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Standard resistance: 0.3-100 Ω
3. Measure the resistance between the terminals 2 or 6 and body ground.
  Standard resistance: More than 0.5 MΩ
  
  If the resistance value is not as specified, replace the actuator assembly.
Inspect A.D.D. actuator operation :
Apply battery positive voltage between the terminal 2 or 6, and check the actuator operation by sound, A.D.D. status and continuity between the terminal 3 and 4.

Fig 2: A.D.D. Actuator Operation Applied Voltage Testing Chart
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

If the operation is not as specified, replace the actuator assembly.
Inspect limit switch continuity :
1. Connect the actuator connector.
2. Shift the transfer shift lever or switch the transfer operation switch to "H2" position.
  
  Fig 3: Setting Limit Switch To H2
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Check the A.D.D. actuator operation by sound.
4. Disconnect the actuator connector.
5. Check the continuity between each terminal, as shown in the chart.
  
  Fig 4: Limit Switch Continuity Specification Chart For H2 Position
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
6. Connect the actuator connector.
7. Shift the transfer shift lever or switch the transfer operation switch to "H4" position.
  
  Fig 5: Setting Limit Switch To H4
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
8. Check the A.D.D. actuator operation by sound.
9. Disconnect the actuator connector.
10. Check the continuity between each terminal, as shown in the chart.
  
  Fig 6: Limit Switch Continuity Specification Chart For H4 Position
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
11. Connect the actuator connector.
Inspect A.D.D. relay :
1. Check the continuity between each terminal, as shown in the chart.
  
  Fig 7: Identifying ADD Relay Terminals
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  Fig 8: A.D.D. Relay Continuity Specifications Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Apply battery positive voltage between each terminal and check the continuity between each terminal, as shown in the chart.
  
  Fig 9: A.D.D. Relay Applied Voltage Specifications Chart
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  If continuity is not as specified, replace the relay.
INSPECT TRANSFER 4WD POSITION SWITCH . (See page TR-10 or TR-15)
Remove A.D.D. actuator . See REMOVAL .
Inspect clutch hub and clutch sleeve :
1. Check the clutch hub and clutch sleeve for wear and damage.
  If necessary, replace them.
2. Check that clutch sleeve slides smoothly on the clutch hub.
  
  Fig 10: Inspecting Clutch Sleeve
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Measure sleeve fork and clutch sleeve clearance :
Using a feeler gauge, measure the clearance between the sleeve fork and clutch sleeve.

Maximum clearance: 0.35 mm (0.0138 in.)

If the clearance exceeds the maximum, replace the fork or sleeve.

Fig 11: Measure Clearance Between Sleeve Fork & Clutch Sleeve
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002