1st generation Sierra (GMT800) · GMT800 · 1,623 complaints, 1,412 with mileage
Owners filed 1,623 complaints with NHTSA about the 1999–2006 Gmc Sierra 1500, and 1,412 of them record the mileage at which the failure happened. That is enough to show not just what fails, but when.
Failures are spread across the mileage range, with the middle half between 47,982 and 115,000 miles. The median is 76,079 miles.
The most-reported areas are the hydraulic brake circuit (24.2% of complaints, typically around 70,000 miles), the brakes (21.3% of complaints, typically around 100,000 miles), the electrical system (14.5% of complaints, typically around 66,667 miles).
| System | Complaints | Share | Typical mileage | Middle half |
|---|---|---|---|---|
| Service Brakes, Hydraulic | 393 | 24.2% | 70,000 | 42,245–99,101 |
| Service Brakes | 345 | 21.3% | 100,000 | 70,000–135,250 |
| Electrical System | 236 | 14.5% | 66,667 | 47,000–90,000 |
| Steering | 75 | 4.6% | 51,000 | 18,000–90,000 |
| Power Train | 60 | 3.7% | 60,000 | 18,000–110,000 |
| Air Bags | 55 | 3.4% | 99,500 | 51,800–155,000 |
| Structure | 50 | 3.1% | 86,500 | 60,000–139,000 |
| Suspension | 45 | 2.8% | 70,143 | 25,000–106,500 |
| Parking Brake | 38 | 2.3% | 55,000 | 24,000–107,788 |
| Fuel System, Gasoline | 38 | 2.3% | 74,947 | 48,138–100,000 |
| Year | Complaints | With mileage |
|---|---|---|
| 1999 | 182 | 144 |
| 2000 | 215 | 183 |
| 2001 | 171 | 148 |
| 2002 | 192 | 172 |
| 2003 | 210 | 184 |
| 2004 | 253 | 224 |
| 2005 | 218 | 194 |
| 2006 | 182 | 163 |
Complaints about this generation are not spread evenly across the vehicle, and the systems that generate the most of them do not all fail at the same point in a car's life. The median failure across all systems here is 76,079 miles; the figures below show which parts of the car run ahead of that and which run behind.
The hydraulic brake circuit accounts for 24.2% of complaints (393 reports, 355 of them with a mileage figure), with a median of 70,000 miles, close to the vehicle's overall pattern. The middle half of these reports falls between 42,245 and 99,101 miles.
The brakes account for 21.3% of complaints (345 reports, 323 of them with a mileage figure), with a median of 100,000 miles, close to the vehicle's overall pattern. The middle half of these reports falls between 70,000 and 135,250 miles.
The electrical system accounts for 14.5% of complaints (236 reports, 201 of them with a mileage figure), with a median of 66,667 miles, close to the vehicle's overall pattern. The middle half of these reports falls between 47,000 and 90,000 miles.
The steering accounts for 4.6% of complaints (75 reports, 63 of them with a mileage figure), with a median of 51,000 miles, close to the vehicle's overall pattern. The middle half of these reports falls between 18,000 and 90,000 miles.
The transmission and driveline accounts for 3.7% of complaints (60 reports, 55 of them with a mileage figure), with a median of 60,000 miles, close to the vehicle's overall pattern. The middle half of these reports falls between 18,000 and 110,000 miles.
The airbag system accounts for 3.4% of complaints (55 reports, 42 of them with a mileage figure), with a median of 99,500 miles, close to the vehicle's overall pattern. The middle half of these reports falls between 51,800 and 155,000 miles.
Within this generation, complaint volume is not constant across model years. The 2004 model year drew the most — 253 complaints — while 2001 drew the fewest at 171. The median year sits at 201.
No recall campaigns covering this generation appear in NHTSA's post-2010 recall file. That is not the same as an absence of problems — recalls address safety defects specifically, and many of the complaints above concern faults that are expensive or annoying without meeting that threshold.
Of the 1,623 complaints filed against this generation, 104 reported a crash; 27 reported a fire; 62 reported an injury; 2 reported a fatality. Crash-involved reports represent 6.4% of the total.
These are owner-reported outcomes, not verified investigations, and they are not adjusted for how many of these vehicles are on the road. They are included because the distinction between a fault that strands a car and a fault that causes a collision is the one that matters most, and it is not visible in a complaint count alone.
For a buyer, failures on this generation are spread rather than concentrated: the middle half falls between 47,982 and 115,000 miles, with a median of 76,079. There is no single mileage threshold to watch, which means condition and maintenance records are more informative than the odometer.
On inspection, the hydraulic brake circuit and the brakes are where this generation's reports concentrate, so those are the areas worth a specific look. The hydraulic brake circuit in particular shows a median failure mileage of 70,000, which gives a concrete number to compare against the odometer of any car you are considering.
None of this is a substitute for a pre-purchase inspection on the individual car. Aggregate patterns describe a population; the example in front of you has its own history.
Instrument cluster stepper motor (gauge motor) failure causing erratic, sticking or dead speedometer, tachometer and fuel gauge. So widespread GM issued a warranty extension on the cluster.
4L60-E / 4L65-E 3-4 clutch pack failure producing slipping on the 3-4 shift and eventual loss of drive.
Fuel level sending unit failure from sulfur deposits on the sender card, giving false or stuck fuel readings.
Transfer case encoder motor failure on 4WD/AWD models causing shift-mode failure and stuck-in-neutral conditions.