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Service bulletins for the 2021 Ram 1500

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

1129 on file from NHTSA, as of 2026-10-19.

About P1D90 on the 2021 Ram 1500: what the code means, and the bulletins and recalls about the same components.

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By component

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Only bulletins with trouble code: P1D90 are shown. Show all

Bulletins, newest first
S2621000003 REV.A2026-03-18. Service bulletin. POWER TRAIN. The vehicle will exhibit a service transmission/check engine warning indicator for the following transmission models: 845RE, 8HP45, 850RE, 8HP50, 8HP70, 8HP75, 8HP75-PHEV, 8HP75-LCV, 8HP90, 8HP95. Transmissions may exhibit the following diagnostic codes: P07E4, P1DB2, P0716, P1B14, P0733, P1D90, P1DB7, P1B13.
S26210000032026-03-05. Service bulletin. POWER TRAIN. Service transmission/check engine warning indicator for the 850RE, 8HP50, 8HP70, 8HP75, 8HP75-PHEV transmissions that have fault codes P07E4, P1DB2, P0716, P1B14, P0733, P1D90, P1DB7, P1B13.
0900321REVA2022-09-26. Service bulletin. POWER TRAIN. Transmission Oil Cooler Lines Not Fully Connected This bulletin involves inspecting the Transmission Oil Cooler (TOC) lines and reconnectingif necessary. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find one or more ofthe following Diagnostic Trouble Codes (DTCs). P1D90-00 Incorrect Gear Ratio - Clutch 2 Defective. P1D91-00 Incorrect Gear Ratio - Clutch 3 Defective. P1D92-00 Incorrect Gear Ratio - Clutch 4 Defective. P1D93-00 Incorrect Gear Ratio - Clutch 5 Defective. P1D95-00 Tcm Clutch Failure Undetermined. P1B14-00 Park-By-Wire - Unintended Park Position. P1B13-00 Park-By-Wire - Unintended Out Of Park Position. P1D99-00 Incorrect Gear Ratio: Clutch B Or E Defective. P1D9A-00 Incorrect Gear Ratio: Clutch C Or D Defective. P1D95-00 Tcm Clutch Failure Undetermined. P07E4-00 Unable To Engage Park. P1DCD-00 Tcm Monitoring Processor Performance - Multiple Clutches Locked Up. P0735-00 Gear 5 Shift Incorrect Ratio. P0919-00 Gear Shift Position Control Error. Customers may also experience the following:Transmission fluid leaking under vehicle. The vehicle will not shift. Slow shifting between gears.
09003212022-09-26. Service bulletin. POWER TRAIN. Transmission Oil Cooler Lines Not Fully Connected This bulletin involves inspecting the Transmission Oil Cooler (TOC) lines and reconnecting if necessary. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find one or more ofthe following Diagnostic Trouble Codes (DTCs). P1D90-00 Incorrect Gear Ratio - Clutch 2 Defective. P1D91-00 Incorrect Gear Ratio - Clutch 3 Defective. P1D92-00 Incorrect Gear Ratio - Clutch 4 Defective. P1D93-00 Incorrect Gear Ratio - Clutch 5 Defective. P1D95-00 Tcm Clutch Failure Undetermined. P1B14-00 Park-By-Wire - Unintended Park Position. P1B13-00 Park-By-Wire - Unintended Out Of Park Position. P1D99-00 Incorrect Gear Ratio: Clutch B Or E Defective. P1D9A-00 Incorrect Gear Ratio: Clutch C Or D Defective. P1D95-00 Tcm Clutch Failure Undetermined. P07E4-00 Unable To Engage Park. P1DCD-00 Tcm Monitoring Processor Performance - Multiple Clutches Locked Up. P0735-00 Gear 5 Shift Incorrect Ratio. P0919-00 Gear Shift Position Control Error. Customers may also experience the following:Transmission fluid leaking under vehicle. The vehicle will not shift. Slow shifting between gears.
09-003-21 REV. A2021-04-26. Service bulletin. EXTERIOR LIGHTING; POWER TRAIN. Transmission Oil Cooler Lines Not Fully Connected This bulletin involves inspecting the Transmission Oil Cooler (TOC) lines and reconnectingif necessary. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find one or more ofthe following Diagnostic Trouble Codes (DTCs). P1D90-00 Incorrect Gear Ratio - Clutch 2 Defective. P1D91-00 Incorrect Gear Ratio - Clutch 3 Defective. P1D92-00 Incorrect Gear Ratio - Clutch 4 Defective. P1D93-00 Incorrect Gear Ratio - Clutch 5 Defective. P1D95-00 Tcm Clutch Failure Undetermined. P1B14-00 Park-By-Wire - Unintended Park Position. P1B13-00 Park-By-Wire - Unintended Out Of Park Position. P1D99-00 Incorrect Gear Ratio: Clutch B Or E Defective. P1D9A-00 Incorrect Gear Ratio: Clutch C Or D Defective. P1D95-00 Tcm Clutch Failure Undetermined. P07E4-00 Unable To Engage Park. P1DCD-00 Tcm Monitoring Processor Performance - Multiple Clutches Locked Up. P0735-00 Gear 5 Shift Incorrect Ratio. P0919-00 Gear Shift Position Control Error. Customers may also experience the following:Transmission fluid leaking under vehicle. The vehicle will not shift. Slow shifting between gears.
09-003-212021-04-26. Service bulletin. POWER TRAIN; EXTERIOR LIGHTING. Transmission Oil Cooler Lines Not Fully Connected This bulletin involves inspecting the Transmission Oil Cooler (TOC) lines and reconnecting if necessary. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find one or more ofthe following Diagnostic Trouble Codes (DTCs). P1D90-00 Incorrect Gear Ratio - Clutch 2 Defective. P1D91-00 Incorrect Gear Ratio - Clutch 3 Defective. P1D92-00 Incorrect Gear Ratio - Clutch 4 Defective. P1D93-00 Incorrect Gear Ratio - Clutch 5 Defective. P1D95-00 Tcm Clutch Failure Undetermined. P1B14-00 Park-By-Wire - Unintended Park Position. P1B13-00 Park-By-Wire - Unintended Out Of Park Position. P1D99-00 Incorrect Gear Ratio: Clutch B Or E Defective. P1D9A-00 Incorrect Gear Ratio: Clutch C Or D Defective. P1D95-00 Tcm Clutch Failure Undetermined. P07E4-00 Unable To Engage Park. P1DCD-00 Tcm Monitoring Processor Performance - Multiple Clutches Locked Up. P0735-00 Gear 5 Shift Incorrect Ratio. P0919-00 Gear Shift Position Control Error. Customers may also experience the following:Transmission fluid leaking under vehicle. The vehicle will not shift. Slow shifting between gears.
09-014-202021-03-01. Service bulletin. EQUIPMENT; POWER TRAIN; EQUIPMENT ADAPTIVE/MOBILITY. Transmission Oil Cooler Line Not Fully Connected This bulletin involves inspecting the Transmission Oil Cooler (TOC) lines and reconnectingif necessary. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may find one or more ofthe following Diagnostic Trouble Codes (DTCs).P1D90-00 Incorrect Gear Ratio - Clutch 2 Defective. P1D91-00 Incorrect Gear Ratio - Clutch 3 Defective. P1D92-00 Incorrect Gear Ratio - Clutch 4 Defective. P1D93-00 Incorrect Gear Ratio - Clutch 5 Defective. P1D95-00 Tcm Clutch Failure Undetermined. P1B14-00 Park-By-Wire - Unintended Park Position. P1B13-00 Park-By-Wire - Unintended Out Of Park Position. P1D99-00 Incorrect Gear Ratio: Clutch B Or E Defective. P1D9A-00 Incorrect Gear Ratio: Clutch C Or D Defective. P1D95-00 Tcm Clutch Failure Undetermined. P07E4-00 Unable To Engage Park. P1DCD-00 Tcm Monitoring Processor Performance - Multiple Clutches Locked Up. P0735-00 Gear 5 Shift Incorrect Ratio. P0919-00 Gear Shift Position Control Error. Customers may also experience the following:Transmission fluid leaking under vehicle. The vehicle will not shift. Slow shifting between gears.

The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.