--- title: "Sierra 2500 DEF tank connector overheats on 2020 and 2021 trucks" kind: "owner-report" recall: false brand: "gmc" model: "sierra-2500" year: 2021 slug: "gmc-sierra-2500-def-connector" url: "https://www.rigfixhq.com/issues/gmc/sierra-2500/2021/gmc-sierra-2500-def-connector" markdownUrl: "https://www.rigfixhq.com/issues/gmc/sierra-2500/2021/gmc-sierra-2500-def-connector.md" --- # Sierra 2500 DEF tank connector overheats on 2020 and 2021 trucks Owner reports are not official NHTSA recalls. Each report cites a public complaint, bulletin, forum thread, or manufacturer page. It is not a failure rate, a diagnosis, or a repair procedure. **Owner report** · Engine · 2021 GMC Sierra 2500 ## Symptoms GM service update N212342980, released January 2022, says the DEF tank connector on certain 2020 and 2021 GMC Sierra 2500HD trucks with the 6.6-liter diesel, RPO L5P, may overheat and set codes P10D9, P143C, and P10F3, which reduces engine speed. The same update names 2020 and 2021 Sierra 3500HD and Chevrolet Silverado 2500HD and 3500HD trucks with that engine. A dealer message dated January 20, 2022, says the U.S. vehicles involved are approximately 38,000. That count is GM's. Dealers reprogram the reductant control module. The update says no parts are required. NHTSA complaints on the 2020 and 2021 Sierra 2500 describe DEF failures. They do not name N212342980. Complaint ODI 11457481, on a 2020 Sierra 2500, says the DEF system failed, the wire harness burned out, the tank failed, and the truck went into limp mode. The owner wrote that they personally know 3 others with the same issue. That count is the owner's. Complaint ODI 11456825 says the DEF tank system failed on a truck the owner calls under warranty, 18 months old, purchased in August 2020, with 20,000 miles. About six weeks before the March 15, 2022 filing, a dealer said no DEF tanks were available. The owner wrote that a shutdown would leave the truck at a reduced speed. Complaint ODI 11454084 says the DEF emission system failed, that the components needed replacement, and that parts were unavailable. Complaint ODI 11741364, on a 2021 Sierra 2500, says a service DEF system message locked speed at 55 mph, that an initial check showed a malfunctioning module, and that it had been happening for the last year to 18 months. Complaint ODI 11746749, on a 2021 Sierra 2500HD Denali, says the truck has the 6.6-liter Duramax and what the filing calls an Allison 10-speed. While under warranty, the owner wrote, the aftertreatment fuel injector was replaced and later the reductant control module. The service update says to reprogram that module and lists no parts. At about 154,833 miles the transmission was replaced at the owner's expense. That transmission job is a different repair in the same filing. Less than 5,000 miles later the owner got a Service DEF System warning, and the DEF tank, DEF heater assembly, and a NOx sensor were replaced. A 2020 Sierra 3500 complaint, ODI 11648405, names bulletin N212342980, says the DEF heater connection arced and melted, and says the truck still failed after the bulletin work. That is a 3500, not this model. A 2020 Silverado 2500 complaint, ODI 11717625, also names N212342980 after a dealer found an overheated DEF tank connector. These Sierra 2500 filings do not show an overheated connector on every 2020 or 2021 truck. ## Likely causes The service update says the DEF tank connector may overheat and set P10D9, P143C, and P10F3. The Sierra 2500 complaints describe a burned harness, a failed tank, a malfunctioning module, and a replaced reductant control module. They do not list those three codes, and they do not name the update. The update's repair is a reprogram with no parts. A replaced module or a replaced tank is a different repair. The filings do not include a measured reason the connector overheated. ## Common fixes If the truck locks speed and shows a service DEF message, get off the road when you can. That is what these complaints describe. Do not treat 55 mph as a way to finish a tow. The service update tells a dealer to reprogram the reductant control module when the VIN shows Open. It lists 0.2 hour under labor operation 9105960 if the module is already at that software, and 0.3 hour under 9105961 for the reprogramming. Ask the dealer to look up N212342980 for the VIN, and ask whether they are reprogramming the module or replacing the tank and harness. The 2021 owner wrote that the module was replaced, and later that the tank and heater were replaced. Those are that owner's repairs, not the no-parts reprogram in the update. ## DIY difficulty Not a driveway job in these sources. The service update is written for a dealer. The complaints describe dealer diagnosis. There is no published procedure here. ## Parts needed The service update says no parts are required for the reprogram. The complaints describe a DEF tank, a wiring harness, a reductant control module, a DEF heater assembly, and a NOx sensor. They do not give a part number. ## Warranty notes This is not a recall. N212342980 is a service update. It expires at the end of the involved truck's new-vehicle limited warranty, and the VIN has to show Open before the work starts. The 2020 tank complaint says that truck was under warranty and that no tank was available. The 2021 owner wrote that an earlier module replacement was under warranty, and that a later transmission replacement was at the owner's expense. A complaint is not a coverage decision, a failure rate, or a diagnosis for another Sierra 2500. The years on this page are 2020 and 2021, which are the years the update and these complaints name. The same update names the 2020 and 2021 Silverado 2500, which has its own page. The 2023 and 2024 valve-body report on this model is a different page. Recall 24V-797 is a different campaign, for certain 2020 through 2022 diesel transmission valves. ## Sources - [GM service update N212342980, which names the 2020-2021 Sierra 2500HD](https://static.nhtsa.gov/odi/tsbs/2022/MC-10206819-0001.pdf) - [NHTSA complaints for 2020 GMC Sierra 2500 (ODI 11457481, 11456825, and 11454084)](https://api.nhtsa.gov/complaints/complaintsByVehicle?make=GMC&model=SIERRA+2500&modelYear=2020) - [NHTSA complaints for 2021 GMC Sierra 2500 (ODI 11741364 and 11746749)](https://api.nhtsa.gov/complaints/complaintsByVehicle?make=GMC&model=SIERRA+2500&modelYear=2021) - [NHTSA complaints for 2020 Chevrolet Silverado 2500 (ODI 11717625 names N212342980)](https://api.nhtsa.gov/complaints/complaintsByVehicle?make=CHEVROLET&model=SILVERADO+2500&modelYear=2020) - [NHTSA complaints for 2020 GMC Sierra 3500 (ODI 11648405 names N212342980 on a 3500)](https://api.nhtsa.gov/complaints/complaintsByVehicle?make=GMC&model=SIERRA+3500&modelYear=2020) Year page: [2021 GMC Sierra 2500](https://www.rigfixhq.com/issues/gmc/sierra-2500/2021) HTML page: https://www.rigfixhq.com/issues/gmc/sierra-2500/2021/gmc-sierra-2500-def-connector