General Motors. LLC (GM) has decided that a problem exists in certain 2019-2023 Chevrolet 4500HD, 5500HD, and 6500HD medium-duty trucks. The brake pressure sensor assembly could leak brake fluid into the brake pressure switch and cause an electrical short circuit.
GM opened an investigation in August 2022 following reports of a vehicle fire on a 2019 Chevrolet Silverado medium-duty truck. As part of that investigation, GM reviewed field data potentially related to the problem and warranty returned brake pressure sensors.
While a series of tests failed to duplicate the condition, in January, a warranty-returned sensor and harness were identified as exhibiting signs of heat damage. This part was subjected to more detailed analysis, including X-ray scans and a chemistry laboratory analysis. The results from these analyses revealed the presence of brake fluid past the diaphragm seal, into the brake pressure switch, and through the actual wire harness into the pump’s fuse circuit. An inspection of the returned components also revealed delamination of the corrosion-inhibiting sealant, which allowed slow seepage of the brake fluid past the diaphragm seal.
According to the defect report, a zinc-nickel plating and sealant used to inhibit corrosion within the pressure sensor assembly may cause delamination of the sealant which results in small fragments of sealer underneath the diaphragm during assembly which allows brake fluid to slowly seep past the seal and into the pressure switch. 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 fuse, the circuit can generate enough heat and could result in a fire. An under-hood fire may occur when the vehicle is off and possibly unattended.
Owners are advised to park outside and away from structures until the recall repair is complete. Dealers will replace the master cylinder pressure sensor and inspect the wire harness. If the harness is damaged, it will be replaced as well. Interim letters notifying owners of the safety risk are expected to be mailed on May 29, 2023. Second letters will be mailed once the remedy is available. GM’s number for this recall is N222375270 and the NHTSA campaign number is 23V-266.