1999 GMC Sonoma Problems

What owners report

Owners of this 1999 GMC Sonoma most often describe seat recline and adjustment parts breaking, and brake failures, lockups and fluid loss. Other complaints describe stalling, hard starts or erratic idle, tailgate cables and hinges breaking, and airbags that did not deploy or deployed late in a crash. Mileage is listed in many of the complaints and ranges from 8,000 to 180,000 miles, so the reports span both low and high mileage trucks.

1. 1
   Seats

   Seat recline and adjustment parts break

   • 10 complaints (18%)
   • median 55,000 mi at 5.5 yrs old (3 state mileage, few)
   • 1 mention a crash, fire or injury
   • filed 2000–2006

   Owners describe seat recline handles, adjuster parts and seat tracks breaking, in some cases leaving the seat stuck flat or in one position. Some say the handle broke again after an earlier replacement, and others say a seat adjuster failed or the seat would not lock in place. Some complaints say the seat part broke after the warranty had expired, and one says the manufacturer first declined to pay for a repair. The complaints that list mileage report about 51,000 and 55,000 miles, and several say a handle broke again after an earlier repair or after the warranty had expired.

   What to check: Test both seat recline handles and the driver seat adjuster, and ask whether any handle, track or adjuster has been replaced before. Owners report repeat breakage, so request repair records and parts receipts.

   2 excerpts from owner complaints in NHTSA records

   “The driver's seat adjust failed. No pressure--could be put on the seat without it moving to the full back position. The dealer initially replaced this in mar 05 after me and dealer speaking with Gmc customer satisfaction. Gmc reimbursed me for costs. 15 months [!!] later, it failed again. The dealer had only seen this issue twice, both times with my car. Gmc initially declined to pay for the repair. …”

   NHTSA complaint #10165075, filed 2006-08, 55,000 miles

   “Diferential has a zuming vibrating and cliking noise when driving both ajustable seat handels broke and 3rd small door handel has never work properly and keeps breaking.”

   NHTSA complaint #10054519, filed 2004-01, 51,000 miles
2. 2
   Brakes

   Brake failures, lockups and fluid loss

   • 9 complaints (16%)
   • median 100,000 mi at 14.1 yrs old (3 state mileage, few)
   • 2 mention a crash, fire or injury
   • filed 1999–2017

   Owners describe brakes that lock up under light pressure, a caliper that failed in a closed position and wore out calipers and rotors on both sides, and a pedal that went to the floor after a master cylinder failure. Other complaints describe brake lines that rusted and burst after a panic stop, and brakes that failed in a collision. One owner describes an ABS warning light with a brake pedal that needed hard pressure, and in some cases the dealer could not find a cause. The complaints that list mileage report about 32,900 and 100,000 miles, and several describe brake trouble during stops, including a panic stop and a front brake that locked at under 30 mph.

   What to check: Ask for brake service records, including any caliper, rotor, master cylinder or brake line replacement. Have a technician check the brake fluid, look for rust on the lines, and check pedal feel during a test drive.

   2 excerpts from owner complaints in NHTSA records

   “During a panic stop the brake system light came on and the brakes felt soft but still worked. During the drive the brakes became very weak. When I checked the brake fluid it was empty. I refilled it and started checking for leaks. I found that both the front and rear brake lines we fractured because of the pressure during the panic stop causing the rusted lines to burst. This seems to be a known ( but not reported) problem for this truck in the northern area..”

   NHTSA complaint #11054621, filed 2017-12, 100,000 miles

   “The accident that happened in october wasn't reported because it was a single vehicle accident and the pavement was wet. I figured it was my fault and not the brakes. At the second accident, the pavement was dry and the collision was was a result of the brakes failing. I can only conclude that brakes during the first time were a compelling factor to the accident. I went to the dealership to complain about problems I had been experienceing with the brakes before both accidents. …”

   NHTSA complaint #715677, filed 1999-12
3. 3
   Electrical system

   Stalling, hard starts or erratic idle

   • 9 complaints (16%)
   • median 83,500 mi at 11.4 yrs old (4 state mileage, few)
   • 1 mention a crash, fire or injury
   • filed 1999–2017

   Owners describe engines that stall while driving, lose power, or do not start without a boost. In one case the vehicle lost power and power steering at highway speed, stalled, and the dealer diagnosed the ignition switch as needing replacement. Another describes stalling and smoke near the battery, and others report an idle that rises and falls between about 1,600 and 3,000 rpm, where the dealer replaced several parts and then said the behavior was normal. The complaints that list mileage report about 26,000 and 156,000 miles, and the stall and start problems occur while driving at highway speed or during startup.

   What to check: Ask the dealer to scan for stored codes and to check the ignition switch, idle motor and throttle positioner, since complaints mention replacing these parts. A test start, a short idle check and a highway drive can show whether the engine stalls or idles erratically.

   2 excerpts from owner complaints in NHTSA records

   “I have encountered several different chevy/Gmc vehicles that are experiencing a lagging start and in some cases no start without a boost. My Sonoma has the lag and I have a few friends that have blazers and full size trucks as well. The variation of engine sizes that are affected has me perplexed. I have attempted to run codes with no fault results. This occurs every time I attempt a startup.”

   NHTSA complaint #10253811, filed 2009-01, 26,000 miles

   “When vehicle is in or out of gear engine idles, RPM will flucuate between 1600-3000 intermittently.dealer ehas replaced idle motor, throttle positioner, new computer , and new software for computer.after several attempts to correct defect, dealer is claiming it is normal.”

   NHTSA complaint #853284, filed 1999-11
4. 4
   Air bags

   Airbags did not deploy or deployed late in a crash

   • 5 complaints (9%)
   • median 91,350 mi at 11.6 yrs old (2 state mileage, few)
   • 5 mention a crash, fire or injury
   • filed 1999–2017

   Owners describe collisions, including a hit into the rear of another vehicle at about 35 mph and a head-on hit at about 10 mph, in which the driver or passenger airbags did not deploy. In other cases the airbags did not deploy after a collision with a cow at about 65 mph or a hydroplane into a tree at highway speed. One complaint describes airbag deployment that was delayed after a low-speed crash into a ditch, with severe injuries, and says no police report was filed. The complaints that list mileage report about 42,700 and 140,000 miles, one at about 65 mph and one at 5 mph on a flooded dirt road.

   What to check: Ask whether the airbag system was checked after any collision, and request the crash and repair records. Some complaints say the vehicle was not diagnosed or repaired after an impact, so written records help show what was checked.

   2 excerpts from owner complaints in NHTSA records

   “While driving 65 MPH consumer hit a cow in the road, and the air bags did not deploy. Took vehicle to dealership, where the mechanic had not resolved the problem.”

   NHTSA complaint #10044857, filed 2003-10, 42,700 miles

   “While driving at 10 MPH consumer was hit head-on by another vehicle on driver's side. Upon impact, driver's side and passenger's side air bags didn't deploy. Driver sustaine d lower back injury. Is currently in physical therapy.”

   NHTSA complaint #837641, filed 1999-06
5. 5
   Body and structure

   Tailgate cables and hinges break

   Mentioned in 4 of 46 sampled complaints

   Owners describe a tailgate cable or hinge breaking while the tailgate was being opened, and in one case the tailgate fell after both cables snapped as the owner stepped off it. One says the cables were corroded from the inside. Some complaints say a tailgate hinge recall did not cover their vehicle, and several say the dealer had not inspected the truck or that the manufacturer was contacted without a repair. The complaints that list mileage report failures from about 45,000 to 125,501 miles, and most describe a cable or hinge breaking as the tailgate was opened.

   9 related service bulletins

   What to check: Open and close the tailgate, and check the cables and hinges for slack or corrosion. Ask whether a tailgate cable service bulletin applies to this VIN and whether any cable or hinge has been replaced.

   2 excerpts from owner complaints in NHTSA records

   “While stepping off of tailgate, both cables snapped and the tailgate fell off of pickup. No broken bones, but bumps and scrapes. Cables are sealed, except for the ends, where water must have gotten into them and corroded the cable from the inside.”

   NHTSA complaint #10291011, filed 2009-11, 125,501 miles

   “The contact stated the passenger side cable broke while attempting to open the tailgate. There is a NHTSA recall, # 06v066000, regarding the tailgate: hinge and attachments. The vehicle has the same problems as indicated in the recall; however it is not included in the recall due to the VIN. No repairs have been made. Updated 03/28/06.”

   NHTSA complaint #10152551, filed 2006-03, 45,000 miles

Buying note. For this model year, check the seat recline handles and adjusters, the brakes and the tailgate cables during inspection, since these areas appear repeatedly in the complaints. Ask for records of brake, ignition or tailgate repairs, and consider a test drive that includes startup and highway speed.

Summary written with AI from a sample of 46 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.