Inverter May Fail Causing Loss of Power – 2019-2022 Proterra Catalyst 800V & ZX5 800V Transit Buses

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OMB Control No.: 2127-0004 Part 573 Safety Recall Report 23V-697 The information contained in this report was submitted pursuant to 49 CFR §573 Manufacturer Name : Proterra Operating Company, Inc. Submission Date : OCT 17, 2023 NHTSA Recall No. : 23V-697 Manufacturer Recall No. : TBD Manufacturer Information : Manufacturer Name : Proterra Operating Company, Inc. Address : 1815 Rollins Road Burlingame CA 94010 Company phone : 4380000 Population : Number of potentially involved : 238 Estimated percentage with defect : 100 % Vehicle Information : Vehicle 1 : 2019-2022 Proterra 40’ and 35′ Catalyst 800V Transit Bus with ProDrive 1.0; 40’ and 35′ ZX5 800V Transit Bus with ProDrive 1.0 Vehicle Type : BUSES, MEDIUM & HEAVY VEHICLES Body Style : OTHER Power Train : HYBRID ELECTRIC Descriptive Information : The recall population consists of 800V ProDrive 1.0 transit buses equipped with a PowerPhase 250 HD traction inverter from the supplier identified in this report (the “PP250 Inverter”). All 800V ProDrive 1.0 transit buses equipped with a PP250 Inverter are subject to this recall. The recall population was determined through a review of Proterra’s production records. Approximately 238 vehicles are in the recall population. Production Dates : SEP 13, 2019 – JAN 06, 2023 VIN Range 1 : Begin : NR End : NR Not sequential Description of Defect : Description of the Defect : The PP250 Inverters at issue in this recall were manufactured with a defective thermal paste that fails to adequately transfer heat away from the insulatedgate bipolar transistor (“IGBT”) contained within the inverter. Over time, the lack of adequate heat transfer may cause the IGBT to overheat and fail. Such failure of the IGBT would result in the loss vehicle propulsion and power steering. FMVSS 1 : NR FMVSS 2 : NR Description of the Safety Risk : Loss of vehicle propulsion and power steering could increase the risk of a crash. Description of the Cause : The PP250 Inverters at issue in this recall were manufactured with a defective thermal paste that may cause the IGBT to overheat and fail over time. Part 573 Safety Recall Report 23V-697 Page 2 The information contained in this report was submitted pursuant to 49 CFR §573 Identification of Any Warning that can Occur : A warning light(s) will appear in the driver’s dash display when an abnormally high temperature and/or erratic rate of increased temperature is detected in or around the IGBT. The diagnostic codes associated with these warnings may be accessed by the operator using the Proterra diagnostic tool and/or telemetry systems. The available diagnostic code history on vehicles that experienced a failure indicates that the operator will receive a warning light(s) and may access the relevant diagnostic codes with adequate time to remove the vehicle from service and inspect the issue in accordance with Proterra’s forthcoming fleet check instructions. Involved Components : Component Name 1 : PP250 Inverter Component Description : Inverter Component Part Number : 1000T-040; 11319418; 11323541 Supplier Identification : Component Manufacturer Name : Danfoss Power Solutions Address : 2800 East 13th Street Ames Iowa 50010 Country : United States Chronology : In May 2021, certain vehicles in the recall population began to experience inverter failures. Proterra investigated the issue, including the engineering analyses and extensive discussions with the supplier of the PP250 Inverter. Amongst other issues, Proterra and the supplier discussed the PP250 Inverter’s sensors, which are intended to self-regulate the IGBT temperature and thermal stress. Between May 2021 and January 2023, Proterra returned failed PP250 Inverters to the supplier to perform a physical inspection and analysis. Proterra and the supplier reviewed event logs, mileage, build dates, and fault codes. Further, the parties examined various sub-components, including, without limitation, the IGBT modules and controller coolant plate where the thermal paste was applied. In July 2023, Proterra met with a third-party expert regarding thermal interface materials in power electronic systems. Part 573 Safety Recall Report 23V-697 Page 3 The information contained in this report was submitted pursuant to 49 CFR §573 Through its investigation, Proterra determined that the thermal paste used by the supplier to manufacture the PP250 Inverters is defective. On October 10, 2023, Proterra’s Safety Committee voted to initiate this voluntary recall. As of October 17, 2023, Proterra has received 48 field or service reports and the same number of warranty claims related to this issue. No injuries or accidents have been reported related to this issue. Description of Remedy : Description of Remedy Program : Remedy parts are not currently available. Proterra is continuing to work with the supplier of the PP250 Inverter to implement a remedy program, including the utilization of a new thermal paste for the manufacture of remedy parts. Proterra will notify NHTSA and the affected vehicle owners when a remedy plan is available. How Remedy Component Differs from Recalled Component : The remedy component will not use the defective thermal paste in the PP250 Inverter. Identify How/When Recall Condition was Corrected in Production : Proterra is currently manufacturing vehicles using an inverter from a different supplier than the supplier that manufactured the defective inverter. Recall Schedule : Description of Recall Schedule : Proterra will notify affected owners about this recall on or before November 14, 2023 Planned Dealer Notification Date : NOV 07, 2023 – NOV 14, 2023 Planned Owner Notification Date : NOV 07, 2023 – NOV 14, 2023 * NR – Not Reported

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