2002 GMC Sierra 2500HD Problems: 3 Known Issues

On the 1999-2003 GMC Sierra 2500HD, the steel brake pipes routed along the frame rails of 1999-2003 Sierra 2500/2500HD trucks corrode from the outside in where road salt, debris and moisture collect against them. The line eventually perforates and dumps hydraulic pressure, giving the driver a pedal that sinks to the floor with little or no braking on the affected circuit. NHTSA opened an investigation (PE10-010, later upgraded to engineering analysis EA11-001) covering roughly six million 1999-2003 GM full-size trucks and SUVs and received 890 consumer complaints, 761 of them from salt-belt states. The agency closed the probe in April 2015 without ordering a recall, advising owners instead to wash the undercarriage - which means there is no free remedy and this remains an owner-paid inspection item.

On the 2001-2004 GMC Sierra 2500HD 6.6L Duramax V8 (RPO LB7), the 2001-2004 6.6L Duramax RPO LB7 uses injectors buried under the valve covers that are notorious for failing well before 150,000 miles. GM's own analysis attributed the failures to fuel injector body cracks, ball seat erosion, and high-pressure seal extrusion. A leaking injector dumps unburned diesel into the cylinder and past the rings into the crankcase, raising the oil level and diluting it. Owner reporting on duramaxforum.com and silveradosierra.com consistently puts first failures in the 100k-150k range, and because the injectors sit under the valve covers the labor to reach them is far higher than on the later LLY/LBZ engines, where injectors are accessible from the top. This is an LB7-only failure mode - the LLY and later injectors were redesigned and do not share it.

On the 2001-2014 GMC Sierra 2500HD, the electric-shift NV246/NV263 transfer case on Sierra 2500HD trucks is positioned by an encoder motor mounted to the case, with a sensor ring inside it reporting shaft position back to the Transfer Case Control Module. Moisture and road salt corrode the encoder motor and its sensor ring, and the dash selector switch itself develops open contacts. When the TCCM loses a valid position signal it illuminates "Service 4WD" and refuses to shift. The classic pattern owners describe is a truck that will still drop into 4LO but will not engage 4HI, because the module can drive the case to its travel extremes but cannot stop it at the intermediate position. C0327 is the code that identifies it.