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Home >> Saab >> 1991 >> 900 SPG >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Computerized Engine Controls >> Fuel Injection Control Unit >> Power Circuits
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Power Circuits

  1. Check for battery voltage between ECU terminal No. 4 (Red wire) and ground. If battery voltage is not present, repair Red wire to main distribution terminal on battery bracket.
  2. Turn ignition on. Check for battery voltage between ECU terminal No. 35 (Green/White wire) and ground. If battery voltage is not present, check fuse No. 14 on 900 Series, or fuse No. 13 on 9000 Series. Fuse panel is located in left side of engine compartment on 900 Series; behind panel inside glove compartment on 9000 Series. If fuse is okay, check for open Green/White wire between fuse box and ECU terminal No. 35, or check for a defective ignition switch.
  3. Turn ignition on. Check for battery voltage between ECU terminal No. 9 and ground. If battery voltage is not present, check for open wire from ECU terminal No. 9 to main relay terminal No 2. On 900 Series, wire is Brown/White to fuel injector terminal block, and Blue/Red to main relay. On 9000 Series, wire is Gray/White to terminal block, and Blue/Red to main relay. If wire is okay, see MAIN RELAY  .
  4. Connect DVOM between ground and ECU terminal No. 1 (Blue wire). Turn ignition switch to START position. Voltage should be higher than 6.5 volts ONLY when ignition switch is in START position.
  5. If voltage is not present, check for open Blue wire between terminal No. 1 of fuel injection ECU unit and terminal No. 29 of ignition ECU.
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