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 MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 390 (HORNS)REPAIR INSTRUCTIONSHORN RELAY REPLACEMENTREMOVAL PROCEDURE

1999 GMC Forward Control 5.7 R, Automatic

Removal Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Removal Procedure

WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

Open the hood.
Remove the cover from the underhood electrical center.

Fig 1: Identifying Underhood Electrical Center Cover

G01755419

Courtesy of GENERAL MOTORS CORP.

Using J 43244, remove the horn relay (1) from the underhood electrical center.

Fig 2: Identifying Horn Relay

G01755420

Courtesy of GENERAL MOTORS CORP.

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.