Why does my diesel truck's DEF consumption suddenly increase?
A sudden spike in DEF consumption usually means the SCR system is dosing more fluid to compensate for inefficient NOx conversion, often…
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Heavy-Duty Vehicles & Fleet
Practical, step-by-step fixes for heavy-duty vehicles & fleet problems — 62 published so far.
Why does my diesel truck's DEF system keep throwing a P20EE code?
A P20EE code means your diesel truck's DEF system isn't converting NOx properly, usually because the DEF fluid is contaminated, the injector…
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Why does my diesel truck's DEF system keep throwing codes after refill?
Contaminated or stale diesel exhaust fluid (DEF) is the most common cause of recurring DEF system codes after a refill — even…
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Why does my diesel truck's DEF system keep throwing codes and going into derate?
A DEF system derate usually means the aftertreatment can't meet emissions targets — most often from a clogged DEF injector, bad NOx…
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Why does my diesel truck's DEF system keep throwing codes and going into limp mode?
A DEF system throwing codes and forcing limp mode usually means contaminated diesel exhaust fluid, a failed NOx sensor, or a clogged…
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Why does my diesel truck's DEF system keep throwing codes?
DEF system codes usually mean contaminated fluid, a clogged injector, a failed NOx sensor, or a faulty dosing valve — not a…
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Why does my diesel truck's DPF filter clog so quickly on short urban routes?
Short trips prevent the diesel particulate filter from reaching the 600°C needed for passive regeneration, so soot accumulates until the ECU forces…
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Why does my heavy-duty diesel truck keep going into limp mode after a DPF regeneration?
Your truck enters limp mode after DPF regeneration because the soot load didn't drop enough, often due to a clogged filter, failed…
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Why does my heavy-duty diesel truck keep going into limp mode with a DEF quality fault?
Your truck enters limp mode with a DEF quality fault because the urea concentration is out of spec — usually from contaminated,…
See the fixWhy does my heavy-duty diesel truck keep going into limp mode?
Limp mode activates when your truck's computer detects a serious fault in the emissions, fuel, or transmission systems and limits power to…
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Why does my heavy-duty diesel truck's DEF consumption suddenly increase?
A sudden spike in DEF consumption usually means a leaking DEF injector, a faulty NOx sensor, or a malfunctioning SCR catalyst causing…
See the fixWhy does my heavy-duty truck's battery drain overnight when parked?
A parasitic draw from accessories like telematics, a fridge, or a faulty alternator diode drains the battery overnight. Test with a multimeter…
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