P1121 on the 2018 Mack Terrapro
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.
| K86900043 | 2019-07-15. Service bulletin. Exhaust Gas Recirculation (EGR) System - Fault Codes SPN 412 FMI 0,2,5; Diagnostic Trouble Codes (DTC) P040A, P040B, P1121 - Temperature Sensor Inspection |
|---|---|
| K52535491 | 2019-05-20. Service bulletin. Diagnostic / Troubleshooting Procedures For EGR System Components; Diagnostic Trouble Codes (DTC) P0401-00, P0402-00, P04DD-00, P1121-00, P1121-98 Or SPN 2659 FMI 16, SPN 2659 FMI 18, SPN 412 FMI 0, SPN 412 FMI 15 - US10, US10+OBD13, US14+OBD*, US17+OBD* With A Variable Geometry Turbocharger (VGT) |
2 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.