Engine-Codes - Generic - U0121

U0121 Code - Lost Communication With Anti-Lock Brake System Control Module

- Code Popularity: 84,344 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC U0121?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Anti-Lock Brake System (ABS) Control Module
  • Anti-Lock Brake System Control Module harness is open or shorted
  • Anti-Lock Brake System Control Module circuit poor electrical connection
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How to Fix the DTC U0121?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the U0121 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the U0121 Code Mean?

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines. Since communication relies on a voltage differential between the two bus lines, the CAN bus is NOT sensitive to inductive spikes, electrical fields, or other noise. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Anti-Lock Brake System (ABS) Control Module has not been received.

Pictures shown may vary from actual

U0121 Code - Lost Communication With Anti-Lock Brake System Control Module

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Code U0121 Information for Specific Makes

  • U0121 Buick Lost Communication With Electronic Brake Control Module
  • U0121 Cadillac Lost Communication With Electronic Brake Control Module
  • U0121 Chevrolet Lost Communication With Electronic Brake Control Module
  • U0121 Chrysler Lost Communication With Anti-Lock Brake System Module
  • U0121 Dodge Lost Communication With Anti-Lock Brake System Module
  • U0121 Ford Lost Communication With The Anti-lock Brake System Control Module  📷
  • U0121 GMC Lost Communication With Electronic Brake Control Module
  • U0121 Honda Lost Communication With Anti-Lock Brake System Control Module
  • U0121 Hummer Lost Communication With Electronic Brake Control Module
  • U0121 Infiniti Lost Communication With Anti-Lock Brake System Control Module
  • U0121 Jeep Lost Communication With Anti-Lock Brake System Module
  • U0121 Lincoln Lost Communication With The Anti-lock Brake System Control Module  📷
  • U0121 Mazda Lost Communication With The Anti-lock Brake System Control Module  📷
  • U0121 Mercury Lost Communication With The Anti-lock Brake System Control Module  📷
  • U0121 Nissan Lost Communication With Anti-Lock Brake System Control Module
  • U0121 Pontiac Lost Communication With Electronic Brake Control Module
  • U0121 RAM Lost Communication With Anti-Lock Brake System Module
  • U0121 Saturn Lost Communication With Electronic Brake Control Module

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