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 MANUALSBUICK1987REGAL GRAND NATIONALREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSIS5.0L FEEDBACK CARBURETOR TESTS W/CODESCHART A5 - "SERVICE ENGINE SOON" LIGHT INOPERATIVE
1987 Buick Regal Grand National
Chart A5 - "Service Engine Soon" Light Inoperative
1987 Buick Regal Grand NationalSECTION Chart A5 - "Service Engine Soon" Light Inoperative
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- 1) This checks for blown gauge fuse or open in "SERVICE ENGINE SOON" light circuit (including I.P. connector), printed circuit and "SERVICE ENGINE SOON" light. Normal response is light on.
- 2) This test checks for shorted ECM. A grounded ECM terminal "G" will turn the "SERVICE ENGINE SOON" light off. If disconnecting the ECM turns light on, ECM is shorted. Normal response is light on.
- 3) This test checks for grounded wire from terminal "C" of light driver to terminal "G" of ECM, an open circuit to terminal "B" of light driver, a bad ground or faulty light driver. Normal reading is about 9 to 11 volts. Over 11 volts indicates a bad ground or a faulty light driver.
- 4) This test checks for open in wire to terminal "B". Normal reading is approximately battery voltage.
- 4A) This test checks for an open wire to terminal "E" from the "SERVICE ENGINE SOON" light. With terminal "E" grounded, normal response is light on.
- 5) This test checks for a grounded wire from driver terminal "C" to ECM terminal "G". Normal response is light on.
RENDER: 1.0x
NO RELATED
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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.