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 282 (ENGINE CONTROLS - TROUBLE SHOOTING - NO CODES)SYMPTOMSVEHICLE SURGES OR CHUGGLESSENSOR/SYSTEM CHECKS
1999 GMC Forward Control 5.7 R, Automatic
Sensor/System Checks
1999 GMC Forward Control 5.7 R, AutomaticSECTION Sensor/System Checks
WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
- Check the Heated Oxygen Sensors (HO2S). The HO2S should respond quickly to different throttle positions. If they do not, check the HO2S for contaminants from the fuel, improper use of RTV, sensors may have a White powdery coating. This will result in a high but false signal voltage (rich exhaust indicated). The Powertrain Control Module (PCM) will reduce the amount of fuel delivered to the engine causing a severe driveability condition.
- Check the Mass Airflow (MAF) sensor and intake air system for proper connections.
- Check the Exhaust Gas Recirculation (EGR) system for proper operation.
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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.