Exhaust And
DPF Repair

Diesel particulate filter service at Torpedo begins with a differential pressure test and soot load estimate from the truck’s aftertreatment control module. We determine whether the filter requires a forced active regen, a bake-and-blow cleaning, or full replacement — avoiding unnecessary replacements while ensuring the filter is restored to acceptable flow restriction.

DPF cleaning is performed using a thermal bake process to convert soot to ash followed by a pneumatic blow-down to remove the ash from the filter substrate. Flow testing before and after cleaning confirms the filter has been restored to within the manufacturer’s acceptable backpressure range before it is reinstalled in the truck.

• Differential pressure sensors tested and replaced if out of calibration
• DPF outlet temperature sensor operation confirmed after cleaning
• Forced regen performed post-install to verify full system function

EGR valve inspection covers electronic actuator function, valve seat condition, and cooler leak testing. A stuck-open EGR valve is one of the most common causes of excessive idle smoke, poor fuel economy, and persistent derate codes on modern diesel engines. We test valve operation under live conditions rather than relying solely on fault codes to confirm the failure.

EGR cooler failures — where exhaust gases leak into the coolant circuit — cause coolant consumption, white smoke, and eventual coolant contamination of the engine oil. We pressure test the EGR cooler with the engine at operating temperature to identify internal leaks that may not produce fault codes in early stages of failure.

• EGR differential pressure sensor tested with every EGR job
• EGR tube and gasket replaced as a set with the cooler or valve
• Cooling system integrity verified after any EGR cooler repair

Selective catalytic reduction system service covers the DEF tank, pump, dosing injector, and the SCR catalyst itself. DEF quality sensor testing confirms the urea concentration is within specification — contaminated or diluted DEF is a frequent cause of SCR efficiency codes and derate conditions that do not resolve with simple regens.

DEF dosing injector testing verifies spray pattern, flow rate, and injector tip condition. A clogged or leaking dosing injector causes uneven SCR catalyst dosing, leading to ammonia slip codes, NOx efficiency failures, and accelerated catalyst degradation. Injectors are cleaned or replaced and the SCR inlet temperature confirmed before system clearance.

• DEF pump pressure tested at the dosing unit inlet
• NOx sensor upstream and downstream of catalyst tested for accuracy
• Full aftertreatment diagnostic cycle run after all SCR repairs

The diesel oxidation catalyst is the first stage of the diesel aftertreatment system and is responsible for converting hydrocarbons and carbon monoxide while raising exhaust temperatures for active DPF regeneration. A failed or contaminated DOC prevents the system from achieving regen temperature, leading to excessive DPF soot load and eventual derate.

DOC substrate inspection is performed using a borescope to identify oil fouling, physical damage, and melt-down from unburned fuel events. Oil-contaminated DOC units cannot be cleaned and must be replaced. We identify the source of the oil contamination — typically a leaking turbo seal or valve cover — before installing a replacement to prevent repeat failure.

• DOC inlet temperature verified with calibrated pyrometer
• Exhaust back pressure tested upstream of DOC to identify restrictions
• Turbo and engine oil consumption evaluated with every DOC inspection

Aftertreatment diagnostic scanning at Torpedo uses OEM-level software to access the aftertreatment control module directly — reading regen history, DPF soot and ash load estimates, NOx readings at the catalyst inlet and outlet, and dosing system event logs. This data-driven approach identifies systemic failures that cannot be found by fault codes alone.

Derate and shutdown conditions caused by aftertreatment faults are resolved by addressing the root cause of the failure — not just clearing codes. A truck that re-enters derate within hours of a code clear has an unresolved underlying failure. We confirm full regen completion and post-repair system performance before any truck is released.

• Regen history and inhibit events reviewed before any repair recommendation
• All aftertreatment fault codes cleared only after verified repair
• Extended idle test performed to confirm derate condition is resolved