General Motors have identified a problem affecting certain 2017-2019 Chevrolet Silverado and GMC Sierra 2500/3500 trucks manufactured with the Duramax diesel 6.6 litre engine and the optional block-heater power cable.

Contamination of the sealing surface of the block-heater heater element can allow a coolant leak to develop. If leaking coolant contacts the block heater cable terminals while the cable is plugged into an energy source a short could occur.

In February 2021, a GM quality manager submitted a report to GM’s Speak Up For Safety program after inspecting an engine-block heater recovered from a 2019 model year Chevrolet Silverado 3500. The owner reported sparking from under the hood after the engine block heater was plugged in. The block heater was leaking coolant, and the engineer observed thermal damage at the connection between the heater and the block heater power cable. This vehicle had previously been fixed for this condition under NHTSA recall 19V-328.

Further investigation identified nineteen potential fires involving engine-block heaters in vehicles remedied under 19V-328. Based on this data, GM opened a formal product investigation and found 122 complaints and 24 reports of potential fires between December 3, 2019 and May 28, 2021 involving vehicles that received the recall remedy under 19V-328. Based on this data GM decided to conduct a safety recall on these vehicles.

Dealers will disable the block heater. GM will provide free replacement block heaters and cords under a separate customer satisfaction campaign. For vehicles previously included in recall 19V-328, the heater cord will be replaced and rerouted. Owner notification letters are expected to be mailed August 16, 2021. GM’s number for this recall is 212329840 and the NHTSA campaign number is 21V-496.