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Home >> Jeep >> 1990 >> Wrangler Laredo, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - CARBURETED >> Microprocessor Control Unit (MCU) (4.2L) >> Power Circuits
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Power Circuits

  1. Using a voltmeter, turn ignition on and check for voltage between MCU terminals No. 1 and 57. If battery voltage is not present, check IGN/LPS fuse. If fuse is okay, check for an open wires between fuse box and control unit.
  2. Connect a voltmeter between ground and MCU terminal No. 58. Turn ignition switch to the START position. Battery voltage should be present between control unit terminal No. 58 and ground. If voltage is not present, check for an open in Green wire between MCU and ignition switch, or check for a defective ignition switch.
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