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 85 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0171: FUEL TRIM SYSTEM LEANDTC PARAMETERS
1999 GMC Forward Control 5.7 R, Automatic
DTC Parameters
1999 GMC Forward Control 5.7 R, AutomaticSECTION DTC Parameters
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
- ECT 140-239°F (60-115°C).
- IAT reading -13-239°F (-25-115°C).
- MAP pressure is more than 26 kPa on M/T or 28 kPa on A/T.
- Engine speed at 550-3600 on A/T or 750-3600 on M/T.
- Vehicle speed less than 82 MPH.
- Fuel level more than 9.8 percent.
- BARO more than 72 kPa.
- No CMP, CKP, ECT, fuel injector, IAT, knock, MAP, misfire, TP, HO2S1, VSS, P0446, P0601, P0602 or P1441 DTCs are set.
DTC sets when LTFT value is more than 165 (29 percent) for more than 16 seconds.
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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.