U0121 on RAM
Lost Communication with ABS Module
U0121 on RAM vehicles indicates lost communication with abs module. Au7o has documented this code across 1 RAM model — most commonly on 1500. U0121 is a network communication code meaning a control module on the vehicle's data bus has lost communication with the ABS (anti-lock brake system) module. Modern cars share information over a CAN bus, and when other modules stop receiving expected messages from the ABS unit, this code sets. Because the ABS module also handles traction control and stability control on most vehicles, you may see multiple warning lights and lost features. It points to a communication or power problem with the ABS module rather than a worn brake part. Typical repair costs on RAM range from $350 to $1,500, depending on the specific model and root cause.
Common Causes of U0121
- •Loss of power or ground to the ABS module
- •Blown fuse feeding the ABS controller
- •Damaged, corroded, or loose ABS module connector
- •Open, shorted, or chafed CAN bus wiring
- •Internal failure of the ABS control module
- •Corrosion or water intrusion in connectors/harness
- •Faulty gateway module disrupting bus communication
U0121 on RAM by Model
RAM 1500(1 issue)
- ABS / Electronic Brake Control Module Internal Failure (C2116 Pump Supply, Brake/ABS Lights)2014-2021
The ABS/Electronic Brake Control Module (EBCM) on Ram 1500 trucks suffers internal electronic failures separate from the software-related ESC recalls. Owners report the ABS, brake, traction-control and related warning lights coming on together with stored codes such as C2200 (internal electronic failure), U0121 (lost communication with ABS module) and C2116 (pump motor fault / pump supply low voltage). C2116 in particular is a strong indicator the ABS pump/module itself has failed. The base brakes still function but ABS, stability and traction control are disabled, and the module must be VIN-programmed when replaced.
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View U0121 across all makes →Frequently Asked Questions
What does U0121 mean on RAM?▼
U0121 stands for "Lost Communication with ABS Module." U0121 is a network communication code meaning a control module on the vehicle's data bus has lost communication with the ABS (anti-lock brake system) module. Modern cars share information over a CAN bus, and when other modules stop receiving expected messages from the ABS unit, this code sets. Because the ABS module also handles traction control and stability control on most vehicles, you may see multiple warning lights and lost features. It points to a communication or power problem with the ABS module rather than a worn brake part. On RAM specifically, this code is documented across 1 model.
What causes U0121 on RAM vehicles?▼
Common causes on RAM: Loss of power or ground to the ABS module, Blown fuse feeding the ABS controller, Damaged, corroded, or loose ABS module connector, Open, shorted, or chafed CAN bus wiring, Internal failure of the ABS control module. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U0121 on a RAM?▼
Repair costs on RAM range from $350 to $1,500, depending on the specific model and root cause.
Which RAM models have U0121 documented?▼
Au7o has documented U0121 on 1 RAM model: 1500.