P249E on 2011-2020 GMC Sierra 3500HD — Diesel Particulate Filter Pressure Sensor Intermittent/Erratic (Bank 1)
1 vehicles · 1 makes · $300-$2,000 repair
How to diagnose and fix P249E: most-reported vehicles
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GMC Sierra 3500HD · 2011–2020
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 DEF and transmission warnings simultaneously. Cold weather operation exacerbates DEF system problems as the fluid crystallizes.
Common Symptoms
- DEF warning message on dash
- Reduced engine power / limp mode
- Check engine light with SCR-related codes
- Service Exhaust Fluid System message
- Transmission warning alongside DEF warning (shared wiring)
- DEF system not heating in cold weather
How to Fix
Scan the SCR/DEF system for stored DTCs and inspect the DEF tank harness where it runs with the transmission wiring, as chafed or shorted wires commonly cause both DEF and transmission warnings at the same time. Test the DEF tank heater, reductant quality/level sensor, and pump module; replace the failed heater or complete DEF tank header/sensor assembly as needed, repair damaged wiring with updated pigtails, clean any crystallized DEF contamination, and confirm proper heater operation and reductant quality readings with a scan tool. In cold-weather cases, verify the tank heater is drawing current and that the fluid lines are not frozen before condemning other components. Typical repair cost ranges from about $300-$800 for harness or heater repairs, and $900-$1,800 if the DEF tank/header assembly must be replaced.
Sources for this issue (1)
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P249E code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P249E mean?
P249E stands for "Diesel Particulate Filter Pressure Sensor Intermittent/Erratic (Bank 1)." Despite the label sometimes seen, the standard SAE definition of P249E is 'Closed Loop Reductant Injection Control At Limit – Flow Too High,' a diesel emissions code in the Selective Catalytic Reduction (SCR) system. The SCR system injects diesel exhaust fluid (DEF/AdBlue) into the exhaust to neutralize nitrogen oxides, and the engine computer adjusts the dosing in a closed loop using NOx sensors. This code sets when the system has to push DEF flow to its maximum correction limit to keep emissions in range, signaling the injection control can no longer compensate. It generally indicates a DEF delivery, fluid-quality, or sensor problem rather than a quick fix, and can lead to reduced power or warning countdowns if ignored.
What are the most common causes of P249E?
The most common causes of P249E are: Contaminated, diluted, or incorrect DEF/AdBlue fluid, Clogged or failing DEF injector/dosing valve, Faulty NOx sensor (upstream or downstream), Degraded or failed SCR catalyst, DEF line/tank leak or pump pressure fault, Exhaust leak upstream of the SCR system, Wiring or connector faults in the dosing/sensor circuits. The specific cause varies by vehicle.
How much does it cost to fix P249E?
Repair costs for P249E range from $300 to $2,000, depending on the vehicle and root cause.
Which vehicles are affected by P249E?
Au7o has documented P249E across 1 vehicle models from 1 manufacturers: GMC.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.