AutoCodes - OBDII Code List - U0100 CADILLAC

U0100 CADILLAC - Lost Communication With Engine Control Module

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3    What is this?
Table of contents

U0100 CADILLAC Possible Causes

  • Faulty Engine Control Module (ECM)
  • ECM harness is open or shorted
  • ECM circuit poor electrical connection

How do I fix code U0100 CADILLAC?

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's pins.
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Tech Notes

There is a factory service bulletin for the following Cadillac models:
2007-2010 Cadillac Escalade Models
2007-2010 Cadillac XLR
2009-2010 Cadillac Escalade Hybrid
Cadillac Factory Service Bulletin OBDII Code U0100

Cost of diagnosing the U0100 CADILLAC code

Labor: 1.0

The cost of diagnosing the U0100 CADILLAC code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

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

U0100 CADILLAC 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.
The serial data circuit is how the devices in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the Data Link Connector (DLC), the scan tool can be used to monitor each device for diagnostic purposes and to check for Diagnostic Trouble Codes (DTC). When the ignition switch is in RUN, each device communicating on the serial data circuit sends a state of health message to ensure that the device is operating correctly. When a device stops communicating on the serial data circuit, for example, if the device loses power or ground, the state of health message, it normally sends on the serial data circuit disappears. Other devices on the serial data circuit, which expect to receive that state of health message, detect its absence; those devices, in turn, set a DTC associated with the loss of the state of health of the non-communicating device. The DTC is unique to the device which is not communicating, and one or more devices may set the same code. A loss of serial data communications DTC does not represent a failure of the devices that contain the stored code.
OBDII Code U0100 Cadillac - Lost Communication With Engine Control Module -

More Information

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