Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSAAB1990900 BASE, 2D CONVERTIBLE, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTSRELAYSMAIN RELAY
1990 Saab 900 Base, 2D Convertible, Standard
Main Relay
1990 Saab 900 Base, 2D Convertible, StandardSECTION Main Relay
- 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.
- 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.
- 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.
- 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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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.