U0121
2 owner reports and 83 manufacturer filings across 25 model years from Cadillac, Chevrolet, Chrysler, Ford and others.
Where U0121 shows up
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports |
|---|---|---|---|
| 2016 Chevrolet Suburban | Steering | 7 | — |
| 2016 Chevrolet Tahoe | Steering | 7 | — |
| 2016 Cadillac Escalade | Steering | 6 | — |
| 2016 GMC Sierra | Electrical System | 6 | — |
| 2016 GMC Yukon | Steering | 6 | — |
| 2017 Chevrolet Suburban | Electrical System | 5 | — |
| 2017 Chevrolet Tahoe | Electrical System | 5 | — |
| 2017 Cadillac XT5 | Electrical System | 4 | — |
| 2016 Chevrolet Silverado | Steering | 4 | — |
| 2016 Chevrolet Silverado 2500HD | Equipment | 4 | — |
| 2020 GMC Sierra | Engine And Engine Cooling | 4 | — |
| 2019 Chevrolet Trax | Electrical System | 3 | — |
| 2018 Chevrolet Trax | Electrical System | 3 | — |
| 2017 Chevrolet Trax | Electrical System | 3 | — |
| 2016 Chevrolet Trax | Electrical System | 3 | — |
| 2017 GMC Acadia | Electrical System | 3 | — |
| 2017 Chevrolet Bolt EV | Electrical System | 2 | — |
| 2016 Chevrolet Equinox | Equipment | 2 | — |
| 2016 GMC Terrain | Equipment | 2 | — |
| 2018 Chevrolet Bolt EV | Electrical System | 1 | — |
| 2020 Chevrolet Trax | Equipment | 1 | — |
| 2024 Chrysler Pacifica | Electrical System | 1 | — |
| 2024 Chrysler Voyager | Service Brakes | 1 | — |
| 2018 Ford Focus | Forward Collision Avoidance | — | 1 |
| 2017 Mercedes-Benz C-Class | Electrical System | — | 1 |
A model year appears here because the code is named in its record, not because every one of these vehicles sets it. Counts are mentions in the federal files, not failure rates — nobody publishes the denominator.
What it gets filed under
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names U0121. Quoting the document number at a service desk is often the fastest route to a diagnosis someone has already written down.
- S25230000412025-05-19 · Electrical System
- Vehicle Will Not Shift From Park. Antilock Brake System (ABS) Light On In Cluster. U0121, U1110, U120C Diagnostic Trouble Codes (DTCs) Set. Discussion: If a vehicle has a complaint of will not shift from park and the below DTCs are set, follow the steps below prior to making any repairs. U0121-00-LOST COMMUNICATION WITH ANTI-LOCK BRAKE SYSTEM (ABS) U1110-LOST VEHICLE SPEED MESSAGE U120C-LOST BRAKE
- PIT5713A2020-12-22 · Lane Departure
- This Preliminary information communicates an issue with the engine wiring harness shorting at the left front cylinder head causing any of the following issues: - IPC gauges sweeping while driving - Several IPC warning messages and MIL displayed - Any combination of the following DTC's: U0073 U0100 U0101 U0121 U0128 U0129 U0131 U0140 U0146 U0422 U2413 P0107 P0117 P0119 P0641 C2A07
- 19NA0682020-07-15 · Equipment
- This technical bulletin provides repair information to correct a customer concern of Malfunction Indicator Lamp (MIL) illuminated, intermittent service messages, Erratic Gauges and technician finding DTCs U0073, U0121, U0100 and/or U0101 set.
- PIT5713A2020-05-07 · Engine And Engine Cooling
- This Preliminary information communicates an issue with the engine wiring harness shorting at the left front cylinder head causing any of the following issues: - IPC gauges sweeping while driving - Several IPC warning messages and MIL displayed - Any combination of the following DTC's: U0073 U0100 U0101 U0121 U0128 U0129 U0131 U0140 U0146 U0422 U2413 P0107 P0117 P0119 P0641 C2A07
- 19NA0682019-11-12 · Electrical System
- This technical bulletin provides repair information to correct a customer concern of Malfunction Indicator Lamp (MIL) illuminated, intermittent service messages, Erratic Gauges and technician finding DTCs U0073, U0121, U0100 and/or U0101 set.
- PIT57132019-09-30 · Engine And Engine Cooling
- This Preliminary information communicates an issue with the engine wiring harness shorting at the left front cylinder head causing any of the following issues: - IPC gauges sweeping while driving - Several IPC warning messages and MIL displayed - Any combination of the following DTC's: U0073 U0100 u0101 u0121 u0128 U0129 u0131 U0140 U0146 U0422 U2413 P0107 P0641 C2A07
What U0121 means
Source: SAE J2012 / OBD-IIA module has stopped hearing from the anti-lock brake controller.
A stored code names the test that failed, never the part that caused it. It is the starting point of a diagnosis, not its conclusion — the same code has several possible causes and the cheap one is not always right.
Common questions about U0121
Source: NHTSA files and the OBD-II standardCan I keep driving with U0121 stored?
Nobody can answer that from the code alone, and a site that does is guessing. A steady light generally means the fault was logged and the vehicle is in a reduced-risk mode; a flashing light means stop soon, because a misfiring engine can destroy a catalytic converter in minutes. The safe read of this page is the mileage and the components, not permission.
Does a code mean the car is recalled?
No. Recalls are filed by campaign and matched by VIN, and none of them are triggered by a scan tool. If you want to know whether an open recall applies to one specific vehicle, check the VIN at nhtsa.gov/recalls — that is the only source that settles it.
Why do the counts here differ from other sites?
Because these are not estimates. Every number on this page is a count of documents in NHTSA's own files: manufacturer communications that name the code in their filed summary, and owner complaints that name it in the narrative. We do not model, weight or extrapolate them.
Will clearing the code fix it?
Clearing turns the light off and erases the freeze-frame data a technician would have used to work out what happened. If the condition is still there the code returns, usually within a few drive cycles, and the diagnosis now starts from less information than before.