Before performing a Parked Regen, the engine should be fully warmed and coolant should be above what temperature in Fahrenheit?

• A. 165 F
• B. 185 F
• C. 170 F
• D. 195 F

Answer: (B)

Parked Regen relies on pushing exhaust temperatures high enough to burn off accumulated soot in the diesel particulate filter, and that only happens reliably when the engine and aftertreatment system are up to temperature. Having the coolant above 185°F ensures the engine is in its normal operating range, the thermostat is fully open, and the aftertreatment components reach their working temperatures so the regen can proceed without stressing the system. If the coolant is cooler (around the mid-160s to low-170s), the exhaust won’t reach the necessary heat, and the regen may fail or not complete. A higher coolant temperature (like 195°F) isn’t required and could risk unnecessary heat buildup.