What is the 2008-2016 GMC Sierra 3500HD EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML)?

The exhaust gas recirculation cooler on 6.6L Duramax LMM and LML engines is prone to internal cracking, allowing coolant to enter the EGR system and combustion chamber. Owners experience white steam from the exhaust, unexplained coolant loss, and in severe cases hydrolocking. Thi… Repairs typically run $900-$2,800. Severity: high.

What is the 2007-2019 GMC Sierra 3500HD Silverado/Sierra 3500HD Frame Corrosion and Rust-Through (Salt Belt)?

The fully boxed steel frame on 2007–2019 Sierra 3500HD trucks operating in northern and salt-belt states is susceptible to severe corrosion, particularly around crossmember mounting points, rear spring hanger brackets, and fuel/brake line routing areas. NHTSA received numerous co… Repairs typically run $500-$8,000. Severity: high.

What is the 2011-2022 GMC Sierra 3500HD DPF (Diesel Particulate Filter) Clogging and Regeneration Failure?

The Duramax diesel DPF becomes clogged with soot under low-speed, short-trip, or heavy towing duty cycles that prevent complete passive regeneration. Owners report the truck entering limp mode, reduced power, and repeated active regen cycles that fail to fully clean the filter. G… Repairs typically run $300-$3,500. Severity: high.

What is the 2011-2022 GMC Sierra 3500HD Turbocharger VGT Vane Sticking and Boost Control Failure (Duramax LML/L5P)?

The variable geometry turbocharger (Garrett GT3788VA on LML, and similar VGT on L5P) used on 6.6L Duramax engines develops carbon buildup on the variable vanes, causing them to stick and resulting in loss of boost control. Owners report surging, lack of power under load, black sm… Repairs typically run $200-$3,500. Severity: high.

What is the 2007-2018 GMC Sierra 3500HD Duramax Water Pump Failure and Coolant Leak?

The factory water pump on 6.6L Duramax engines (LBZ, LMM, LML, L5P) is known to develop weep hole leaks and bearing failures, resulting in coolant loss and potential overheating. The plastic impeller on earlier units can also separate from the shaft, causing sudden loss of coolan… Repairs typically run $400-$1,200. Severity: high.

What is the 2015-2023 GMC Sierra 3500HD Trailer brake controller / integrated trailer brake module malfunction?

Sierra 3500HD owners towing heavy loads report intermittent trailer brake output loss, warning messages, or erratic gain behavior from the integrated trailer brake controller. NHTSA complaints and GM service bulletins/diagnostics commonly point to module/software issues, poor con… Repairs typically run $80-$900. Severity: high.

What is the 2011-2019 GMC Sierra 3500HD Hydroboost brake assist loss due to power steering pump/hose failure?

On Sierra 3500HD trucks equipped with hydroboost, a loss of power steering hydraulic pressure can also reduce brake assist. Owners report a sudden hard brake pedal and increased stopping distance, often accompanied by power steering noise or intermittent steering assist. NHTSA co… Repairs typically run $350-$1,600. Severity: high.

What is the 2008-2019 GMC Sierra 3500HD Allison 1000 Transmission Control Module and Sensor Failures?

The Allison 1000 transmission paired with the Duramax diesel in 2008-2015 Sierra 3500HD trucks has a high failure rate for the Transmission Control Module (TCM). A class action suit was filed covering these years. Additional issues include input/output speed sensor failures causi… Repairs typically run $500-$3,500. Severity: high.

What is the 2015-2024 GMC Sierra 3500HD Diesel Injector Failure Causing White Smoke and Rough Running?

The Bosch piezoelectric fuel injectors on the Duramax L5P and LML engines can fail due to contaminated fuel, high-mileage wear, or internal electrical faults. A failed injector causes white smoke on startup, rough idle, misfires on the affected cylinder, and fuel dilution of the… Repairs typically run $600-$5,000. Severity: high.

What is the 2015-2024 GMC Sierra 3500HD Rear Leaf Spring Breakage Under Heavy Loads?

The rear leaf spring packs on the Sierra 3500HD are prone to breaking or cracking under sustained heavy loads, particularly when used for frequent towing, hauling, or with fifth-wheel hitches. The main leaf or secondary leaves fracture at the spring eye or center bolt area. Broke… Repairs typically run $400-$1,500. Severity: high.

What is the 2007-2020 GMC Sierra 3500HD Allison 1000/2000 Series Transmission Torque Converter Shudder?

The Allison 1000 and 2000 series automatic transmissions paired with Duramax engines in the Sierra 3500HD exhibit torque converter clutch shudder during light throttle cruising between 40–65 MPH as the TCC applies and releases. This is caused by degraded transmission fluid, worn… Repairs typically run $150-$2,200. Severity: medium.

What is the 2007-2022 GMC Sierra 3500HD Front Differential Actuator Failure Causing 4WD Engagement Problems?

The front axle disconnect actuator (also called the front axle engagement actuator or IWE—Integrated Wheel End) on four-wheel-drive Sierra 3500HD models is known to fail, preventing proper engagement or disengagement of 4WD. Owners report grinding noises from the front axle area… Repairs typically run $150-$800. Severity: medium.

What is the 2014-2019 GMC Sierra 3500HD A/C condenser leak leading to loss of refrigerant and warm air?

Owners commonly report the A/C stops cooling due to refrigerant leaks at the condenser, often from corrosion, stone impacts, or seam leaks. NHTSA complaints and owner forums frequently describe repeated recharges that only temporarily restore cooling. The issue is most often repo… Repairs typically run $450-$1,400. Severity: medium.

What is the 2007-2019 GMC Sierra 3500HD Glow plug control module / glow plug circuit faults causing hard cold starts (Duramax)?

Duramax-equipped Sierra 3500HD owners report hard starting, extended cranking, and rough idle in cold weather due to glow plug system faults. NHTSA complaints and service information commonly involve failed glow plugs, glow plug control module issues, or wiring/connector problems… Repairs typically run $250-$1,200. Severity: medium.

What is the 2011-2019 GMC Sierra 3500HD Rear axle pinion seal leak and differential fluid loss (AAM 11.5/11.8)?

Owners report gear oil leaks at the rear differential pinion seal, sometimes after towing or sustained highway speeds. NHTSA complaints and owner reports describe oil slinging onto the underbody and a developing howl if fluid level drops. The issue is commonly associated with sea… Repairs typically run $250-$1,200. Severity: medium.

What is the 2011-2020 GMC Sierra 3500HD Diesel Exhaust Fluid (DEF) System Failures?

The Duramax diesel Sierra 3500HD (2011+) equipped with the DEF/SCR emission system develops failures in the DEF tank heater, DEF quality sensor, and associated wiring. Wires to the DEF tank short out, and because they share a harness with the transmission, this can trigger both D… Repairs typically run $300-$2,000. Severity: medium.

What is the 2015-2024 GMC Sierra 3500HD Exhaust Manifold Cracking and Warping (Duramax L5P/LML)?

The cast iron exhaust manifolds on the Duramax diesel engine are prone to cracking and warping due to extreme exhaust gas temperatures and thermal cycling. Cracks typically develop at the manifold-to-head mounting points, causing exhaust leaks that produce a ticking noise on cold… Repairs typically run $800-$2,500. Severity: medium.

What is the 2015-2024 GMC Sierra 3500HD Steering Gear Box Leak and Excessive Play?

The recirculating ball steering gear box on the Sierra 3500HD develops fluid leaks at the input shaft seal and sector shaft seal, leading to power steering fluid loss and increased steering play. The heavy-duty application and large tires accelerate wear on the steering box inter… Repairs typically run $400-$1,500. Severity: medium.

What is the 2007-2019 GMC Sierra 3500HD Blend door actuator failure causing temperature/airflow control problems?

Sierra 3500HD owners report clicking/ticking behind the dash and inability to control cabin temperature due to HVAC blend door or mode door actuator failures. GM service bulletins and owner reports describe stripped actuator gears or actuator motor failures that can leave the tru… Repairs typically run $180-$650. Severity: low.

GMC · Known Issues

2015 GMC Sierra 3500HD Problems: 21 Known Issues

2015 model year · 3,560+ owner reports · Updated September 2026

Share:@au7o.io

According to Au7o's analysis of 3,560+ owner reports, the 2015 GMC Sierra 3500HD has 21 documented known issues, with 11 rated critical. The most serious are CP4.2 High-Pressure Fuel Pump Catastrophic Failure ($10,000-$18,000 repair), EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML) ($900-$2,800 repair), Silverado/Sierra 3500HD Frame Corrosion and Rust-Through (Salt Belt) ($500-$8,000 repair), DPF (Diesel Particulate Filter) Clogging and Regeneration Failure ($300-$3,500 repair), Turbocharger VGT Vane Sticking and Boost Control Failure (Duramax LML/L5P) ($200-$3,500 repair), Duramax Water Pump Failure and Coolant Leak ($400-$1,200 repair), Trailer brake controller / integrated trailer brake module malfunction ($80-$900 repair), Hydroboost brake assist loss due to power steering pump/hose failure.

Frequently Asked Questions

What are the most common GMC Sierra 3500HD problems?

According to Au7o's analysis of 3,560+ owner reports, the 2015 GMC Sierra 3500HD has 21 documented issues. The most frequently reported are: CP4.2 High-Pressure Fuel Pump Catastrophic Failure, EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML), Silverado/Sierra 3500HD Frame Corrosion and Rust-Through (Salt Belt). Of these, 11 are rated critical and should be addressed promptly.

Is the GMC Sierra 3500HD reliable?

The 2015 GMC Sierra 3500HD has 21 known issues documented across 3,560+ owner reports. 11 issues are rated critical: CP4.2 High-Pressure Fuel Pump Catastrophic Failure and EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML) and Silverado/Sierra 3500HD Frame Corrosion and Rust-Through (Salt Belt) and DPF (Diesel Particulate Filter) Clogging and Regeneration Failure and Turbocharger VGT Vane Sticking and Boost Control Failure (Duramax LML/L5P) and Duramax Water Pump Failure and Coolant Leak and Trailer brake controller / integrated trailer brake module malfunction and Hydroboost brake assist loss due to power steering pump/hose failure and Allison 1000 Transmission Control Module and Sensor Failures and Diesel Injector Failure Causing White Smoke and Rough Running and Rear Leaf Spring Breakage Under Heavy Loads. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common GMC Sierra 3500HD problems?

Repair costs for known GMC Sierra 3500HD issues range from $80 to $18,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, CP4.2 High-Pressure Fuel Pump Catastrophic Failure, typically costs $10,000-$18,000 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2011-2020 GMC Sierra 3500HD CP4.2 High-Pressure Fuel Pump Catastrophic Failure?

The Sierra 3500HD Duramax diesel uses the same Bosch CP4.2 high-pressure fuel pump as the 2500HD. The pump is prone to catastrophic failure that destroys the entire fuel injection system (all 6 injectors, fuel rails, return lines). The 3500HD is often used for heavier towing and… Repairs typically run $10,000-$18,000. Severity: high.

All 21 Known Issues

Other GMC Models

Frequently Asked Questions

What are the most common GMC Sierra 3500HD problems?

Is the GMC Sierra 3500HD reliable?

How much does it cost to fix common GMC Sierra 3500HD problems?

What is the 2011-2020 GMC Sierra 3500HD CP4.2 High-Pressure Fuel Pump Catastrophic Failure?

When Issues Typically Appear

2011-2020 GMC Sierra 3500HD: CP4.2 High-Pressure Fuel Pump Catastrophic Failure#

2008-2016 GMC Sierra 3500HD: EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML)#

2011-2022 GMC Sierra 3500HD: Turbocharger VGT Vane Sticking and Boost Control Failure (Duramax LML/L5P)#

2007-2019 GMC Sierra 3500HD: Glow plug control module / glow plug circuit faults causing hard cold starts (Duramax)#

2011-2020 GMC Sierra 3500HD: Diesel Exhaust Fluid (DEF) System Failures#

2008-2019 GMC Sierra 3500HD: Allison 1000 Transmission Control Module and Sensor Failures#

2007-2020 GMC Sierra 3500HD: Allison 1000/2000 Series Transmission Torque Converter Shudder#

2007-2019 GMC Sierra 3500HD: Silverado/Sierra 3500HD Frame Corrosion and Rust-Through (Salt Belt)#

2011-2022 GMC Sierra 3500HD: DPF (Diesel Particulate Filter) Clogging and Regeneration Failure#

2007-2018 GMC Sierra 3500HD: Duramax Water Pump Failure and Coolant Leak#

2015-2023 GMC Sierra 3500HD: Trailer brake controller / integrated trailer brake module malfunction#

2011-2019 GMC Sierra 3500HD: Hydroboost brake assist loss due to power steering pump/hose failure#

2015-2024 GMC Sierra 3500HD: Diesel Injector Failure Causing White Smoke and Rough Running#

2015-2024 GMC Sierra 3500HD: Rear Leaf Spring Breakage Under Heavy Loads#

2007-2022 GMC Sierra 3500HD: Front Differential Actuator Failure Causing 4WD Engagement Problems#

2011-2019 GMC Sierra 3500HD: Rear axle pinion seal leak and differential fluid loss (AAM 11.5/11.8)#

2014-2019 GMC Sierra 3500HD: A/C condenser leak leading to loss of refrigerant and warm air#

2007-2019 GMC Sierra 3500HD: Blend door actuator failure causing temperature/airflow control problems#

2015-2024 GMC Sierra 3500HD: Exhaust Manifold Cracking and Warping (Duramax L5P/LML)#

2015-2024 GMC Sierra 3500HD: Steering Gear Box Leak and Excessive Play#

2015-2020 GMC Sierra 3500HD: Dashboard Instrument Cluster Pixel and Display Failure#