Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSDODGE AND RAM20232500 HD POWER WAGONREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 492 (RADIO FREQUENCY (RF HUB) MODULE - DTCS C1504-07 TO U1517-62 - 2500HD)DTC TROUBLESHOOTINGU0121-00-LOST COMMUNICATION WITH ANTI-LOCK BRAKE SYSTEM (ABS) CONTROL MODULE "A"
2023 Dodge and Ram 2500 HD Power Wagon
U0121-00-Lost Communication With Anti-Lock Brake System (Abs) Control Module "A"
2023 Dodge and Ram 2500 HD Power WagonSECTION U0121-00-Lost Communication With Anti-Lock Brake System (Abs) Control Module "A"
WARNING: This page is about a different car, the 2022 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The COMMUNICATION DIAGNOSTIC PROCEDURE MUST be performed before replacing any component(s) or module(s). Perform the COMMUNICATION DIAGNOSTIC PROCEDURE. Refer to COMMUNICATION DIAGNOSTIC PROCEDURE .
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.