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U0121 HUMMER

U0121 HUMMER - Lost Communication With Electronic Brake Control Module

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3   
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Possible causes

  • Faulty Electronic Brake Control Module (EBCM)
  • EBCM harness is open or shorted
  • EBCM circuit poor electrical connection

Tech notes

There is a factory service bulletin for the following HUMMER models:

2008-2009 HUMMER H2

HUMMER Factory Service Bulletin OBDII Code U0121

Possible symptoms

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

U0121 Hummer Description

Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module.
OBDII Code U0121 Hummer - Lost Communication With Electronic Brake Control Module - AutoCodes.com

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U0121 HUMMER Comments

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