The General Motors GMC Sierra is a workhorse of a truck that’s built for hauling and towing. First introduced in 1962, the Sierra shares many of the same characteristics as the Chevrolet Silverado and has been a popular choice for truck enthusiasts ever since, with “very good” ratings from Consumer Reports in virtually all production years.
But despite its general reliability, the GMC Sierra is not without its share of common problems just like any car. So before you buy one, it’s important to be aware of these common issues so that you can make an informed decision that you won’t regret later.
1. 4WD Transfer Case Sensor/Switch
One of the most common problems with the GMC Sierra is the failure of the 4WD transfer case sensor or switch. A fault in this actuator can cause the truck to get stuck in 4WD mode, or it may not engage 4WD at all when you need it.
There are a few things that can cause this problem, but the most common is simply a worn-out or damaged switch due to water or dirt infiltration. Another potential culprit has to do with the tire size. If the truck has mismatched, overinflated, or underinflated tires, the switch can fail.
Finally, a damaged output shaft seal on the transfer case can also cause this problem. When this seal goes bad for whatever reason, it can lead to hydraulic fluid leaking into the transfer case.
Drivers first noticed this issue popping up in 1991. And unfortunately, it persisted all the way to 2013. Interestingly, 2014 Sierras appear to be void of this issue, as the 4WD transfer case position sensor/selector switch problem did return until the following year and in 2016.
Additionally, mileage doesn’t appear to be a factor in this problem. Sierras with low mileage have been known to experience the same issues as those with high mileage. Some Sierra owners have reported the 4WD transfer case position sensor/switch failing with as few as 5,000 miles.
To make matters worse, this isn’t a cheap fix, as it can cost around $1,000. That includes a $100 diagnosis and a $900 repair. So if you’re looking at buying a GMC Sierra 1500, be sure to check if the 4WD is working properly. If not, this is definitely something you’ll want to get fixed before driving the truck off the lot.
How to Fix
You can do a few different things to help prevent this issue in your GMC Sierra 1500. First, maintain your truck’s tires. Make sure they’re properly inflated and that they match. Secondly, if you live in an area with a lot of dirt and mud, be sure to clean out your truck’s undercarriage regularly to prevent any build-up that could damage the 4WD system.
Thirdly, use your 4WD system once in a while. If you’re just using the Sierra as a daily driver, you might be stuck using 2WD mode. Your 4WD components can seize up when not in use. So every month or so, engage 4WD and drive it for a few hundred yards.
Lastly, if your truck does start to experience this problem, take it to a mechanic as soon as possible to get it fixed. They can check to see if the output shaft seal needs to be replaced and if so, they can take care of it without having to replace the entire unit.
2. Poor Lighting
Lighting is crucial when driving in poor visibility conditions, such as at night or fog. The Sierra can give off weak light. Symptoms and signs of the problem can include dim headlights. Poor lighting while driving can be a major safety issue, as it can make it difficult to see the road ahead.
The most common causes of this problem have to do with GMC’s decision to start using single-filament halogen bulbs in its 3rd generation GMC trucks. These bulbs are used in both low beams and high beams. They don’t last as long as the dual-filament bulbs used in previous models and don’t provide nearly as much light. Fortunately, replacing the bulbs is an easy and inexpensive fix.
Model years that are affected by this problem include 2014 to the present. It’s worth noting that a class-action lawsuit was filed in 2015 for this very issue.
How to Fix
If the headlights are dim because of blown bulbs, the solution is to replace the bulbs. You can buy replacement bulbs at most auto parts stores or online. You can even opt for aftermarket LED bulbs that give off better illumination. Just be sure that they are to-spec and legal in your particular jurisdiction.
3. Heating and Air Conditioning Issues
The HVAC system in the GMC Sierra 1500 may have problems with the blower motor resistor, the blower motor, or the climate control module.
Symptoms may include cold air not working, the fan not working, or the temperature not being set correctly. Causes of these problems may include a blown fuse, a faulty resistor, a bad motor, or a bad module. Unfortunately, the AC components used by GMC in certain model years have relatively poor reliability.
The problem is most common in 2015 GMC Sierras.
How to Fix
You will need to replace the faulty part. The cost depends if it’s the fuse, resistor, motor, or module. When it comes to AC system-related problems, it’s better to consult a specialist. There are more robust aftermarket components that can be used to replace faulty parts as long as they are to-spec. But have a professional do it.
4. Fuel Level Sensor
The GMC Sierra’s fuel level sensor may not be accurate, causing the fuel gauge to read inaccurately. Your truck can run out of gas even when the gauge says there is still fuel in the fuel tank. Once again, the 2015 GMC Sierra 1500 is the primary model affected by this problem.
How to Fix
If you are experiencing this problem, there are a few things you can do in your spare time to try and fix it. One is to recalibrate the fuel level sensor. This can be done by following these steps:
- Disconnect the battery negative cable.
- Remove the fuel pump fuse from the fuse box.
- Wait 10 minutes.
- Reconnect the battery negative cable.
- Replace the fuel pump fuse.
- Start the engine and let it run for a few minutes.
- Turn off the engine and let it sit for a few minutes.
- Start the engine and check the fuel gauge reading.
If this does not fix the problem, you may need to replace the fuel level sensor. Failure to resolve it can lead to engine issues and other problems.
5. Steering Noise (Clunking Sound)
The most common symptom of this problem is a clunking or popping noise that you’ll hear when turning the wheel. You may also feel a vibration in the upper intermediate steering shaft.
There are a few things that can cause this problem, including worn-out suspension components, loose power steering rack bolts, or a loose tie rod end.
This problem has been reported on GMC models from 2013 and 2016.
How to Fix
If you’re experiencing this problem on your GMC Sierra 1500, there are a few things you can do to try and fix it. Worn-out suspension components can often be the cause of this problem, so have them inspected and replaced if necessary. Loose steering rack bolts can also cause a clunking noise, so tighten them up if they’re loose. A loose tie rod end can also cause this issue, so check that component for looseness and tighten it up if necessary.
6. Instrument Panel Glitches
Complaints from owners involving the instrument panel glitches can include blank screens, gauges not working, messages popping up, and more. This is often the result of a cracked dashboard. The model years that are affected include 2014 to 2015.
How to Fix
The problem is resolved by replacing the instrument panel.
7. Vehicle Body Deterioration
A common problem for GMC Sierras is paint peeling and latches breaking. This can be a major problem, as it can lead to rust and other damage to the body of the vehicle.
Symptoms and signs of these problems can include visible damage on any of the vehicle body parts. You’ll be able to see rust, imperfections, and cracks. They may occur in models from 2014 and 2015.
How to Fix
The best way to fix these problems is to have the vehicle repainted and the latches replaced. This can be done at a GMC dealership or a body shop. If you have a newer Sierra, it should be covered by a rust warranty.
Be Sure to Avoid Certain Model Years
The GMC Sierra 1500 is an otherwise reliable vehicle as long as you avoid models from 2014 and 2015. These years seem to be the most susceptible to key problems. In fact, GMC Sierras from these years have been known to have over a thousand complaints, including oil pressure problems and even recalls.
The Sierra does share a lot in common with the Chevy Silverado. You can also try to avoid Sierras from the same model years as these worst Chevy Silverado models.
So do your research and avoid these model years if you can.