AutoCodes - Generic - U1900

U1900 Code - CAN Communication Bus Fault

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3
Table of contents

|U1900 code possible causes

  • Faulty / intermittent ignition switch connections
  • CAN Bus wiring intermittently open/shorted to power or ground
  • Faulty / intermittent connection at PCM
  • Faulty electrical connections at ABS Control Module
  • Faulty electrical connections at the instrument cluster
  • Poor connections at the trailer brake controller/trailer connector

|How do I fix the U1900 code?

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.

|U1900 code tech notes

This is typically a false/intermittent code. It can occur if:
Someone hooks up a scanner to the OBDII port while the ignition is on or while the engine is idling.
A trailer brake system is installed improperly/incorrectly on a truck with ABS (anti-lock brakes).

|Cost of diagnosing the U1900 code

Labor: 1.0

The cost of diagnosing the U1900 code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.

|When is the U1900 code detected?

When the PCM, Brake Controller and Instrument Cluster are unable to communicate with each other at any time while the ignition switch is turned to the “Run” position, code U1900 sets in memory.

|What are U1900 code possible symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • Amber ABS (Anti-lock Brakes) Light ON
  • Wrench Light On

|U1900 code description

The Anti-ock Brakes System (ABS) module, the Powertrain Control Module (PCM), and the instrument cluster communicate over the Controller Area Network (CAN) Bus. This is a high-speed bus communication system and is not fault tolerant, which means any type of intermittent/loose connection between these 3 controllers will cause communication to stop. When the PCM, ABS module and instrument cluster are unable to communicate with each other at any time while the ignition switch is turned on, code U1900 will set.
OBDII Code U1900 - CAN Communication Bus Fault - AutoCodes.com

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|U1900 code comments

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