P1644 on the 2017 Peterbilt 520
The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.
This code is specific to a manufacturer and is not described here. Its meaning is in the manufacturer's service information.
| 34-074 | 2019-05-13. Service bulletin. Non Safety Campaign: Vehicles were built with a 5 bolt supply wire for the air dryer pressure sensor that is no longer required with current architecture. If left in place, a fault code P1644 may be set. |
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1 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.