2021 Gmc SIERRA 3500

Problems, Recalls & Reliability Report

Above Average

Quick Summary

The 2021 Gmc SIERRA 3500 has 28 owner complaints filed with NHTSA — that's 0.3x the segment average of 80. The most common issue is transmission problems (25% of all complaints), specifically: •the diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no eta • my pickup only does 55mph right now and soon to do 5mph you cannot drive on a public road doing 5mph •there is thousands of other people having the same exact problem! •the def light.

Total Complaints

Recalls Issued

—/5

Safety Stars

0.3x

vs Segment Avg

Known Problems

TRANSMISSION

7 complaints

25%

• •The diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no ETA • My pickup only does 55MPH right now and soon to do 5MPH you cannot drive on a public road doing 5MPH •There is thousands of other people having the same exact problem! •The DEF light
• The throttle body gets stuck wide open after the eninge gets up to operating temperature, it will give some warning with the throttle like on off throttle use and no codes show up at all. The risk of everyones is in extrem DANGER. The break are to soft and well not stop unless you put both feet on t
• Problem: Unable to shift transmission from D to another position like R, P, N due to snow/slush being on shifter. I travel on Idaho state highways and County roads that are plowed. In February, I traveled state highway 14. Road conditions were plowed snow roads, broken snow floor, slush and paveme

Typical onset: 50K miles Est. repair: $500

“•The diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no ETA • My pickup only does 55MPH right now and soon to do 5MPH you cannot drive on a public road doing 5MPH •There is thousands of other people having the same exact problem! •The DEF light”

— NHTSA complaint filing

BRAKES

5 complaints

18%

• Trailer brake wiring connection continually disconnectsthen reconnects some time later. Some periods of up to 10 minutes without having trailer braking power. Major safety issue when toeing fifth wheel trailer. We lost brakes going down steep grades. GMC is aware of issue, but has not provided a sol
• The vehicle recently had a recall repaired at the dealership. I subsequently took delivery on it as a BRAND NEW UNIT, and the brakes are extremely soft; to the point where I must depress the pedal to the floor to get it stopped even at slow speeds. I hoped it was just an air bubble from the repair
• The throttle body gets stuck wide open after the eninge gets up to operating temperature, it will give some warning with the throttle like on off throttle use and no codes show up at all. The risk of everyones is in extrem DANGER. The break are to soft and well not stop unless you put both feet on t

Typical onset: 50K miles Est. repair: $500

“Trailer brake wiring connection continually disconnectsthen reconnects some time later. Some periods of up to 10 minutes without having trailer braking power. Major safety issue when toeing fifth wheel trailer. We lost brakes going down steep grades. GMC is aware of issue, but has not provided a sol”

— NHTSA complaint filing

ELECTRICAL

4 complaints

14%

• Trailer brake wiring connection continually disconnectsthen reconnects some time later. Some periods of up to 10 minutes without having trailer braking power. Major safety issue when toeing fifth wheel trailer. We lost brakes going down steep grades. GMC is aware of issue, but has not provided a sol
• Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, someti
• When carrying the electronic key in my pocket the vehicle will lock/unlock presumably due to the remote contacting other items in the pocket. I have owned well over a dozen GM vehicles and never had this issue. I believe the remote design has the lock/unlock buttons too proud of the surrounding surf

Typical onset: 50K miles Est. repair: $500

— NHTSA complaint filing

ENGINE

3 complaints

11%

• •The diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no ETA • My pickup only does 55MPH right now and soon to do 5MPH you cannot drive on a public road doing 5MPH •There is thousands of other people having the same exact problem! •The DEF light
• The throttle body gets stuck wide open after the eninge gets up to operating temperature, it will give some warning with the throttle like on off throttle use and no codes show up at all. The risk of everyones is in extrem DANGER. The break are to soft and well not stop unless you put both feet on t
• Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, someti

Typical onset: 50K miles Est. repair: $500

— NHTSA complaint filing

OTHER

3 complaints

11%

• Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, someti
• Vehicle is put into park after driving. Shift to Park warning comes on while vehicle is in park. Vehicle will not shut off due to this warning and must be left running unoccupied.
• There is a known issue with these trucks with the infotainment screen blacking out, which renders the backup cameras inoperative. This is a huge safety risk and its astounding to me that this hasn't been recalled yet.

Typical onset: 50K miles Est. repair: $500

“Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, someti”

— NHTSA complaint filing

Estimated Repair Costs

TRANSMISSION(~50K mi)

$500

BRAKES(~50K mi)

$500

ELECTRICAL(~50K mi)

$500

ENGINE(~50K mi)

$500

OTHER(~50K mi)

$500

Estimates based on average reported repair costs. Actual costs vary by location, shop, and severity.

🔍 Pre-Purchase Inspection Checklist

Based on 28 owner complaints for this specific year, here's what to check or ask about:

☐
TRANSMISSION: •The diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no ETA • My pickup only does 55MPH right now and soon to do 5MPH you cannot drive on a public road doing 5MPH •There is thousands of other people having the same exact problem! •The DEF light
Typically appears around 50K miles. Repair cost ~$500
☐
BRAKES: Trailer brake wiring connection continually disconnectsthen reconnects some time later. Some periods of up to 10 minutes without having trailer braking power. Major safety issue when toeing fifth wheel trailer. We lost brakes going down steep grades. GMC is aware of issue, but has not provided a sol
Typically appears around 50K miles. Repair cost ~$500
☐
ELECTRICAL: Trailer brake wiring connection continually disconnectsthen reconnects some time later. Some periods of up to 10 minutes without having trailer braking power. Major safety issue when toeing fifth wheel trailer. We lost brakes going down steep grades. GMC is aware of issue, but has not provided a sol
Typically appears around 50K miles. Repair cost ~$500
☐
ENGINE: •The diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no ETA • My pickup only does 55MPH right now and soon to do 5MPH you cannot drive on a public road doing 5MPH •There is thousands of other people having the same exact problem! •The DEF light
Typically appears around 50K miles. Repair cost ~$500
☐
General: Get a pre-purchase inspection from an independent mechanic ($100-$200)