Coolant Leak Under the Vehicle

Some 2020-2022 Silverado 2500/3500 and Sierra 2500/3500 trucks equipped with the 6.6L Duramax diesel engine (RPO L5P) may have a coolant leak under the vehicle. The Check Engine MIL may be illuminated along with DTC P2C48 (Low Temperature Loop Coolant Pump Performance) set in the Engine Control Module. These conditions may be the result of contact between the auxiliary diesel fuel cooler coolant hose and the front driveshaft at the crossmember. This type of contact typically occurs when driving through deeper water or snow.

The auxiliary cooling system is a low-temperature system designed to carry heat away from diesel fuel system components.

Repair any coolant leaks found and, to prevent future contact, re-route the coolant hose away from the front driveshaft. Drill a 6.5 mm-sized hole near the middle of the transmission crossmember. (Fig. 20)


Fig. 20


Add a retainer or equivalent onto the coolant hose and install the retainer into the hole in the crossmember. (Fig. 21)


Fig. 21


For more information and part numbers, refer to Bulletin #21-NA-265.


– Thanks to Kevin Minor

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