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ABS Code U0121-00


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U0121-00-

 

LOST COMMUNICATION WITH ANTI-LOCK BRAKE SYSTEM (ABS) CONTROL MODULE

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Set Conditions:

 

The Body Control Module (BCM) does not receive any CAN Bus messages from the Anti-lock Brake System (ABS).

 

Causes-

ANTI-LOCK BRAKE SYSTEM MODULE (ABS) POWERS AND GROUNDS

 

ANTI-LOCK BRAKE SYSTEM MODULE (ABS)

 

CAN C BUS (+) CIRCUIT OPEN

 

CAN C BUS (-) CIRCUIT OPEN

 

 

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 #1) Battery- tested healthy.

 

 #2) Battery cables and  ground connections cleaned.

 

#3) Check fuses for ABS in the Underhood fuse box. TIPM.

 

Inside the lid shows the fuse diagram.

 

F141 40 amp

F173 25 amp

F156 10 amp

 

 

#4) ABS module grounds. There are 2 ground wires.

 

Passenger strut tower 2 ground studs. 

 

Clean and check for broken wires. 

IMG_20260226_1652042.thumb.jpg.7f4ec35ad2e4e2986f04acb29e20a18b.jpg

Edited by Dean H
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After the previous steps have been done.

 

Using a bi-directional scanner.

 

Check if it can communicate with the abs module.

 

Using a Dodge wiring diagram.

 

Next, would be to check the ABS module connector for damage and any broken wires.

 

The CAN BUS communication

lines are 2 small wires twisted together.

 

The ABS MODULE itself could be shorted out internally.

 

IMG_20260106_0931242.thumb.jpg.2a734eb806142386495abebeba1978c4.jpg

 

The ABS module is hidden up underneath the passenger side cowl in the engine bay.

 

Edited by Dean H
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