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 26 (THEFT DETERRENT SYSTEM)DIAGNOSTIC TESTSDTC P1631: INVALID PASSWORD RECEIVEDCONDITIONS FOR RUNNING DTC
1999 GMC Forward Control 5.7 R, Automatic
Conditions For Running DTC
1999 GMC Forward Control 5.7 R, AutomaticSECTION Conditions For Running DTC
WARNING: This page is about a different car, the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
- DTC P1626 is not active.
- PCM is not in password learn mode.
- Passlock(tm) system is enabled.
- Fuel enable decision point has been reached, or engine is cranking.
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.