Engine-Codes - Mercury - U1900 Mercury

U1900 Mercury Code - CAN Communication Bus Fault

- Code Popularity: 4,610 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
Table of contents
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What are the Possible Causes of the DTC U1900 Mercury?

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 / 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

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).

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How to Fix the DTC U1900 Mercury?

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 U1900 Mercury 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.

When is the 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 Code Possible Symptoms?

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

What Does the U1900 Mercury Code Mean?

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.

U1900 Mercury Code - CAN Communication Bus Fault

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