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 MANUALSGMC1998ENVOY 2WD V6-4.3L VIN WREPAIR AND DIAGNOSISCRUISE CONTROLCRUISE CONTROL MODULEDIAGRAMSDIAGNOSTIC AIDSGENERAL ELECTRICAL DIAGNOSIS PROCEDURESCHECKING AFTERMARKET ACCESSORIES
1998 GMC Envoy 2WD V6-4.3L VIN W
Checking Aftermarket Accessories
1998 GMC Envoy 2WD V6-4.3L VIN WSECTION Checking Aftermarket Accessories
IMPORTANT: Do not connect aftermarket accessories into the following circuits:
^ SIR circuits, all such circuits are indicated on circuit diagrams with the SIR symbol. Refer to SIR Service Precautions Caution in Cautions and Notices.
^ OBDII circuits, all such circuits are indicated on circuit diagrams with the OBDII symbol. Refer to OBD II Symbol Description Notice in Cautions and Notices.
Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problems.
Possible causes of vehicle problems related to aftermarket accessories include:
^ Power feeds connected to points other than the battery.
^ Antenna location.
^ Transceiver wiring located too close to vehicle electronic modules or wiring.
^ Poor shielding or poor connectors on antenna feed line.
^ Check for recent service bulletins detailing installation guidelines for aftermarket accessories.
^ SIR circuits, all such circuits are indicated on circuit diagrams with the SIR symbol. Refer to SIR Service Precautions Caution in Cautions and Notices.
^ OBDII circuits, all such circuits are indicated on circuit diagrams with the OBDII symbol. Refer to OBD II Symbol Description Notice in Cautions and Notices.
Always check for aftermarket accessories (non-OEM) as the first step in diagnosing electrical problems. If the vehicle is so equipped, disconnect the system to verify that these add-on accessories are not the cause of the problems.
Possible causes of vehicle problems related to aftermarket accessories include:
^ Power feeds connected to points other than the battery.
^ Antenna location.
^ Transceiver wiring located too close to vehicle electronic modules or wiring.
^ Poor shielding or poor connectors on antenna feed line.
^ Check for recent service bulletins detailing installation guidelines for aftermarket accessories.
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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.