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Symptoms · Duramax L5P (2017-present)
Duramax L5P (2017-present): overheating or temperature creeping up
2 documented failures on this engine list this among their signs. They are ordered from the most widespread down. Each one shows the signs in its record's own words, how to tell it from the others, the usual fix and any recall or bulletin.
Not sure which engine you have, or want the recalls for your exact truck? Check your VIN: it names the engine and lists the campaigns for that model year. Whether a recall is still open on your VIN: nhtsa.gov/recalls.
verified
How widespread: Common
How it shows up
- high EGTs on grades, creeping coolant temps and lost power under tow when the filter restricts
Its other signs
- regen intervals collapsing from a healthy 400-700 miles to 50-100 miles, with fuel economy dropping to 10-12 mpg highway and constant 'Cleaning Exhaust Filter' messages
- 'Service Exhaust System' messages and false regen triggers from the differential pressure sensor (codes P2452-P2455)
How to tell it apart
- track regen intervals over three tanks: under ~200 miles average at 80k+ miles indicates an ash-loaded DPF
- differential pressure diagnostics: above ~0.5 psi at warm idle or ~3.0 psi at wide-open throttle under load indicates restriction; pressure should read near zero at key-on/engine-off; replace sensor and hose as a pair
- distinguish sensor-fault codes from a genuinely loaded filter before buying hardware
Usual fix
replace the differential pressure sensor + hose when codes are sensor-side; replace or professionally clean the DPF assembly when genuinely ash-loaded
Root cause, parts and sources →
aggregated
How widespread: Occasional
How it shows up
- coolant seep/leak from the water pump weep hole; soft hoses; temperature creep under sustained tow
Its other signs
- the risk is being stranded - vendor framing: routine inspections catch a failing water pump early
How to tell it apart
- pressure-test the cooling system; inspect the water pump weep hole, hoses and thermostat at service intervals
- rule out the EGR path when coolant drops with no external leak (see the EGR record)
Usual fix
replace the water pump / thermostat / worn hoses; refill with the specified coolant
Root cause, parts and sources →
Other symptoms on the Duramax L5P (2017-present)
Hard start, long crank or no-startLoss of power, limp mode or derateMisfire, rough idle, hesitation or surgingDEF, DPF and regeneration warnings
Everything on the Duramax L5P (2017-present)Its recalls and bulletins