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.

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 2007-2014 GMC Sierra 3500HD Transfer case pump rub causing fluid leak and transfer case damage (4WD)?

On 4WD Sierra 3500HD models with GM transfer cases that use an internal pump, owners report a leak caused by the pump wearing through the magnesium case (commonly called "pump rub"). This can lead to low fluid, chain/bearing damage, and eventual loss of 4WD function. The problem… Repairs typically run $450-$2,800. Severity: high.

What is the 2020-2024 GMC Sierra 3500HD Electric power steering (EPS) assist loss / reduced assist warnings (new body style)?

On 2020+ Sierra 3500HD (T1 platform) with electric power steering, owners report intermittent loss of steering assist and warning messages such as "Steering Assist Reduced". NHTSA complaints and GM service information commonly point to EPS module/software issues, wiring/connector… 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 2007-2014 GMC Sierra 3500HD Fuel Tank Strap and Fuel Sender Unit Corrosion Causing Fuel Gauge Inaccuracy?

On 2007–2014 Sierra 3500HD models, the fuel tank mounting straps and the fuel level sender unit are prone to corrosion, causing inaccurate fuel gauge readings and in some cases complete sender failure. NHTSA complaint data documents numerous owners reporting sudden fuel gauge dro… Repairs typically run $250-$900. 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.

GMC · Known Issues

2007-2024 GMC Sierra 3500HD Problems & Issues

2007-2024 model years · 4,005+ owner reports · Updated August 2026

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According to Au7o's analysis of 4,005+ owner reports, the 2007-2024 GMC Sierra 3500HD has 24 documented known issues, with 13 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), Transfer case pump rub causing fluid leak and transfer case damage (4WD). at .

Frequently Asked Questions

What are the most common GMC Sierra 3500HD problems?

According to Au7o's analysis of 4,005+ owner reports, the 2007-2024 GMC Sierra 3500HD has 24 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, 13 are rated critical and should be addressed promptly.

Is the GMC Sierra 3500HD reliable?

The 2007-2024 GMC Sierra 3500HD has 24 known issues documented across 4,005+ owner reports. 13 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 Transfer case pump rub causing fluid leak and transfer case damage (4WD) and Electric power steering (EPS) assist loss / reduced assist warnings (new body style) 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 year GMC Sierra 3500HD is the most reliable?

Reliability varies across model years of the GMC Sierra 3500HD. Based on documented issues, problems are most commonly reported in earlier model years. Au7o recommends checking the specific known issues for your target year before purchasing, and having a pre-purchase inspection performed by a qualified mechanic. Our known issues database covers the 2007-2024 GMC Sierra 3500HD with 24 documented issues documented across 4,005+ owner reports.

All 24 Known Issues

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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 year GMC Sierra 3500HD is the most reliable?

When Issues Typically Appear

CP4.2 High-Pressure Fuel Pump Catastrophic Failure#

EGR Cooler Failure and Coolant Contamination (Duramax LMM/LML)#

Turbocharger VGT Vane Sticking and Boost Control Failure (Duramax LML/L5P)#

Glow plug control module / glow plug circuit faults causing hard cold starts (Duramax)#

Diesel Exhaust Fluid (DEF) System Failures#

Trailer brake controller / integrated trailer brake module malfunction#

Electric power steering (EPS) assist loss / reduced assist warnings (new body style)#

Transfer case pump rub causing fluid leak and transfer case damage (4WD)#

Front Differential Actuator Failure Causing 4WD Engagement Problems#

Rear axle pinion seal leak and differential fluid loss (AAM 11.5/11.8)#

Allison 1000 Transmission Control Module and Sensor Failures#

Allison 1000/2000 Series Transmission Torque Converter Shudder#

Diesel Injector Failure Causing White Smoke and Rough Running#

Fuel Tank Strap and Fuel Sender Unit Corrosion Causing Fuel Gauge Inaccuracy#

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

DPF (Diesel Particulate Filter) Clogging and Regeneration Failure#

Duramax Water Pump Failure and Coolant Leak#

Hydroboost brake assist loss due to power steering pump/hose failure#

Rear Leaf Spring Breakage Under Heavy Loads#

A/C condenser leak leading to loss of refrigerant and warm air#

Blend door actuator failure causing temperature/airflow control problems#

Exhaust Manifold Cracking and Warping (Duramax L5P/LML)#

Steering Gear Box Leak and Excessive Play#

Dashboard Instrument Cluster Pixel and Display Failure#