Ram bulletin 21-029-26 REV. A
What it saysFlash: Transmission Control Module (TCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle may exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs)… NHTSA’s full summary ↓
Ram filed this with NHTSA as a service bulletin dated May 1, 2026, received Apr 15, 2026, about the power train — 2 documents under this number: 21-029-26 and 1 more. It names 4 model years (2026). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationFlash: Transmission Control Module (TCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle may exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ● P0826-00 - Up/Down Shift Switch. ● P0827-00 - Up/down Shift Switch Circuit Low. ● P085F-00 - Up And Down Shift Switch Circuit Range/performance. Customers may also experience one or more of the following: ● Customer is unable to switch the ignition to OFF when in Park gear. ● After shifting into Park, the Instrument Panel Cluster (IPC) will display that the transmission is in Neutral. NOTE: The transmission will actually be in Park and able to hold the vehicle, but the cluster display would indicate Neutral, preventing the engine from shutting off. ● Rough/bumpy 2-3 power on upshifts and/or 3-2 coast down shifts. ● Vehicle enters into limp home mode. Other software improvements: ● Decreased sensitivity to DTCs P1D8A and P1D8B This bulletin involves inspecting and if required reprogramming the TCM with the latest available software
Trouble codes it names: P1D8A P1D8B
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 21-029-26 REV. A | Service bulletin | May 1, 2026 | 11032328 | not found |
| 21-029-26 | Service bulletin | Apr 8, 2026 | 11031330 | not found |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themAlso filed against model years this site has no page for: 2026 Ram 4500; 2026 Ram 5500.
A vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 2 model years this bulletin names have filed 53 complaints with NHTSA since 2015. 7 of them name Power Train — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
I own a Ram 2500 (VIN: ) that has experienced a persistent and worsening rough idle. The engine shakes violently at idle, RPMs fluctuate unpredictably, and the vehicle feels as if it may stall. This occurs at stoplights, in traffic, and after warm-up. The vehicle has been taken to the dealership multiple times for this issue.
2026 Ram 2500 · Power Train · filed with NHTSA Feb 8, 2026
What component or system failed or malfunctioned, and is it available for inspection upon request? Rear Axle Failure - Dealership has the truck currently How was your safety or the safety of others put at risk? - It was not Has the problem been reproduced or confirmed by a dealer or independent service center?
2026 Ram 3500 · Power Train · filed with NHTSA Aug 4, 2026
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the power train
Source: same model, same component group65 other manufacturer communications filed against these Ram models under the same component group (power train), newest first. The eight newest are listed; the rest are on the Ram list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| 114739 | Service bulletin | Sep 24, 2026 | TRANSMISSION KIT - WITH TORQUE CONVERTER |
| 08-302-26 | Service bulletin | Aug 1, 2026 | Flash: Electronic Shift Module (ESM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must… |
| 18-067-26 | Service bulletin | Jul 14, 2026 | Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle mus… |
| 18-066-26 | Service bulletin | Jul 8, 2026 | Seed Request Denied During Technicians may experience the following: SYMPTOM: ● The scan tool displays the message "Seed Request denied" whe… |
| 9100841 | Service bulletin | Jun 25, 2026 | HD Front and Rear Prop Shafts Increase U-Joint Usage If customer concern diagnosis leads to suspect u-joint issue or failure with the prop s… |
| 18-002-26 REV. B | Service bulletin | Jun 24, 2026 | Flash: Powertrain Control Module (PCM) Updates Customers may experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle may… |
| 21-039-26 | Service bulletin | May 8, 2026 | Replace K1 Clutch / Input Shaft Assembly Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhi… |
| 21-028-26 REV. A | Service bulletin | May 1, 2026 | Flash: Transmission Control Module (TCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle m… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Ram, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Ram 21-029-26 REV. A a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the 21-029-26 REV. A repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way.
Which vehicles does 21-029-26 REV. A cover?
The manufacturer filed it against 4 model years: 2026 Ram 2500, 2026 Ram 3500, 2026 Ram 4500, 2026 Ram 5500. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.