GM issues 'do not drive' order for Heavy, Medium Duty trucks over fire risk

General Motors has issued a “do not drive” order for just over 40,000 examples of its 2019-2023 Chevrolet 4500HD, 5500HD, and 6500HD Medium-Duty trucks. They are being recalled to address an issue with brake pressure sensor assemblies that may leak brake fluid into the brake pressure switch and cause an electrical short-circuit that can potentially lead to a fire, the company said. 

“These vehicles may have a brake pressure sensor assembly that allows brake fluid to leak beyond the diaphragm seal into the pressure switch,” GM said in its defect report to NHTSA. “The brake fluid may seep into the sensor’s electrical components and short the brake pressure switch and the associated fuse. If brake fluid shorts the brake pressure switch and the associated fuse, the
circuit can generate excessive heat that could result in a fire, increasing the risk of injury. An underhood fire may occur when the vehicle is off and possibly unattended.”

GM said it has traced the issue to a zinc-nickel plating and sealant used to inhibit corrosion within the pressure sensor assembly. The sealant can delaminate, allowing fluid to seep past the sensor assembly seal over time. GM says owners may see a notice on their dash screens calling for brake service if the system detects the fluid contamination, but the issue may present without symptoms or for too short a period of time for the computer to detect the problem. 

So far, GM has records of 21 incidents of failure in customer trucks, 11 of which resulted in fire, smoke or visible flame. The company is urging customers to park their trucks until they can be brought in for a replacement brake pressure sensor switch. Owners should be notified of the issue by the end of May. 

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