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Circuit Test B16 - Electrical Load Unit (ELU)

Fig 1: ELU Circuits
G108510
NOTE: Enter this test only when directed here from SWITCH MONITOR TEST procedure or CIRCUIT TEST B15, step 2). To prevent replacement of good components, be aware that the following non-EEC components or systems may be at fault: A/C system operation, lighting system, rear defroster or engine cooling fan operation. This test is intended to diagnose only the following: ELU, engine cooling fan switch or related wiring circuits.
  1. Checking System Integrity  - Visually check all wiring, harnesses, connectors and components for evidence of damage, overheating, shorting or looseness. If a fault is found, repair as necessary. If no faults are found, go to the following test steps for the appropriate switch that sent you to this test:
    • Cooling fan switch, step 2).
    • Rear defroster, step 5).
    • Combination switch, step 7).
    • Heater blower, step 8).
  2. Checking Cooling Fan Signal  - Set VOM on 20-volt scale. Disconnect cooling fan motor. With KOEO, ensure all accessories are off and disconnect cooling fan relay No. 1. Measure voltage between "BL/Y" wire terminal (+) of cooling fan relay No. 1 connector and ground (-). If voltage is greater than 7.3 volts, go to next step. If not, go to step 4).
  3. Checking Cooling Fan Switch Operation  - Disconnect cooling fan motor and cooling fan switch. Set VOM on 200-ohm scale. Measure resistance between cooling fan switch and ground. If resistance is less than 5 ohms when engine is cold and greater than 10k ohms when engine is warm, reconnect cooling fan switch and confirm operation of relay No. 1 and wiring. If resistance is not within specification, replace cooling fan switch. Reconnect cooling fan motor.
  4. Checking ELU Output Voltage  - Set VOM on 20-volt scale. With KOEO and ELU connected, ensure cooling fan motor and cooling fan relay No. 1 is disconnected and that all accessories are turned off. Measure voltage between "BL/Y" terminal (+) of electrical load unit and ground (-). If voltage is greater than 7.3 volts, repair "BL/Y" wire from ECU to cooling fan relay No. 1 for an open circuit. Reconnect cooling fan motor and go to step 10).
  5. Check Rear Window Defroster Signal  - Remove 15-amp circuit fuse. Turn off all accessories. Disconnect rear window defroster switch. With KOEO, set VOM on 20-volt scale. Measure voltage at "BK/BL" wire terminal of rear window defroster switch connector. If voltage is greater than 7.3 volts, check operation of rear window defroster switch. If not, go to next step.
  6. Checking ELU Output Voltage  - Ensure ELU is connected. Remove 15-amp circuit fuse. Turn off all accessories. Disconnect rear window defroster switch. With KOEO, set VOM on 20-volt scale. Measure voltage between ELU "BK/BL" wire terminal (+) and ground (-). If voltage is greater than 7.3 volts, repair "BK/BL" wire between ELU and rear window defroster switch for opens. If voltage is 7.3 volts or less, replace fuse and reconnect rear window defroster switch. Go to step 10).
  7. Checking Combination Switch Signal  - Disconnect ELU. With KOEO, ensure all accessories are turned off. Set VOM on 20-volt scale. Turn headlamps on. Measure voltage between "W/BL" wire terminal (+) at ELU and ground (-). If voltage is greater than 6 volts, go to step 10). If not, repair "W/BL" wire from combination switch to ELU for open or shorts. If all circuits are okay, repair combination switch as necessary.
  8. Checking Heater Blower Signal  - Set VOM on 20-volt scale. Disconnect heater control unit. Ensure all accessories are turned off. With KOEO, measure voltage between "BL/BK" wire terminal at heater control unit connector and ground (-). If voltage is greater than 5 volts, repair heater control unit as necessary. If voltage is 5 volts or less, go to next step.
  9. Checking ELU Output Voltage  - Disconnect heater control unit. Ensure all accessories are turned off and ELU is connected. Set VOM on 20-volt scale. Measure voltage between "BL/BK" wire terminal (+) at ELU and ground (-). If voltage is greater than 5 volts, repair "BL/BK" wire for open between ELU and heater control unit. If voltage is not greater than 5 volts, go to next step.
  10. Check For Shorts To Ground  - Disconnect ELU and cooling fan relay No. 1. Ensure all accessories are turned off. Set VOM on 20k-ohm scale. Measure resistance between ground and the following wire terminals at the ELU connector: "BL/GN", "BL/Y", "BK/BL", and "W/BL". If any resistance is less than 10k ohms, repair short(s) to ground. If there are no resistance readings less than 10k ohms, reconnect cooling fan relay No. 1 and go to next step.
  11. Checking For Power At ELU  - Disconnect ELU and set VOM on 20-volt scale. With KOEO, measure voltage between "BK/W" wire terminal (+) at ELU connector and ground (-). If voltage is greater than 10 volts, go to next step. If voltage is 10 volts or less, repair "BK/W" wire between ELU and ignition switch for shorts or opens. Ensure ignition switch is okay.
  12. Checking ELU Ground  - Disconnect ELU and set VOM on 200-ohm scale. Measure resistance between "BK" wire terminal of ELU connector and ground. If resistance is less than 5 ohms, go to next step. If not, repair open in "BK" wire from ELU to ground.
  13. Checking ECA Pin Voltage  - Install breakout box. Ensure all accessories are turned off. With KOEO, set VOM on 20-volt scale. Measure voltage between test pins No. 24 (+) and 20 (ground). If voltage is greater than 7 volts with all accessories off and less than 1.5 volts with headlights and rear defroster on, replace ECA. If voltage is not as specified, repair open or short in "GN/Y" wire from ECA terminal "1F" to ELU. If wire circuit is okay, replace ELU.
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