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Home >> Saab >> 1990 >> 900 SPG, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Relays >> Main Relay
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Main Relay

  1. Disconnect ECU and mass airflow meter connectors. Connect ECU wire harness terminal No. 21 to ground. Voltage should be present at ECU wire harness terminal No. 9 and at mass airflow meter pin No. 5. If not, go to next step.
  2. Remove glove compartment box and pull out fuse/relay panel. Check voltage at main relay pins No. 30 (Red wire) and No. 86 (Red wire). If voltage is not present, check wiring from battery positive source to fuse/relay panel.
  3. Connect main relay terminal No. 85 (Yellow/White wire) to ground. Check voltage at terminal No. 87 (Gray/White wire) and at terminal No. 87B (Brown/White wire). If voltage is present, go to next step. If voltage was not present, replace main relay.
  4. If from step 3), voltage was present. Check the following:
    • Yellow/White wire between main relay terminal No. 85 and ECU pin No. 21.
    • Green/White wire between main relay terminal No. 87 through the pressure switch to fuel pump relay terminal No. 86.
    • Brown/White wire between main relay terminal No. 87B and mass airflow meter pin No. 5.
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