U0121 on Dodge: How to Diagnose & Fix
Lost Communication with ABS Module
1 Dodge model · 1 documented issue · 1 critical · $100-$800 repair
U0121 on Dodge by model: symptoms, diagnosis and fix
The Dodge Magnum suffers from widespread electrical problems centered around the TIPM (Totally Integrated Power Module) and the steering column control module (clockspring). Symptoms include dash lights flickering or going completely dark while driving, headlights cutting out at night, loss of turn signals, wipers, horn, and cruise control all at once. The steering column module failure is particularly dangerous as it can disable multiple safety systems simultaneously. The TIPM relay failures can cause no-start conditions, fuel pump cutouts, and random electrical gremlins throughout the vehicle.
Common Symptoms
- Dashboard lights flickering or going completely dark while driving
- Headlights cutting out intermittently, especially at night
- Loss of turn signals, wipers, horn, and cruise control simultaneously
- Vehicle cranks but will not start intermittently
- Fuel pump stops running randomly while driving
- Warning lights illuminating on dash without clear cause
How to Fix
For steering column module failure (loss of wipers, horn, turn signals, cruise control simultaneously), replace the clockspring assembly ($150-$300 part, $200-$400 labor). For TIPM-related issues, have the relays tested — individual relay replacement is sometimes possible ($50-$150), but full TIPM replacement runs $400-$800 for the module plus programming. For flickering dash lights, check the instrument cluster ground connections and the body harness ground behind the left kick panel.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Mopar 56049795AE clockspring / steering-column control module
Replace when steering-wheel functions and clockspring/module testing isolate this assembly Fitment: Product fitment includes Magnum configurations; verify VIN/options and airbag procedure Live OEM direct-product page when checked
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Sources for this issue (3)
U0121 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0121 mean on a Dodge?
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 Dodge it is documented across 1 model: Magnum.
What are the most common causes of U0121?
The most common causes of U0121 are: 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. The specific cause varies by vehicle.
How much does it cost to fix U0121 on a Dodge?
Published repair estimates on Dodge range from $100 to $800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.