CAN network

U0139 — Lost Communication with Suspension Control Module

Severity: medium Drive with care, to a shop

What U0139 means

U0139 means one or more control units stopped receiving messages from the suspension control module over the CAN bus. That module manages adaptive dampers or air suspension, adjusting ride height and firmness using body-position sensors and a compressor. When it goes silent, the system usually falls back to a default mode or shuts down.

Symptoms

  • Suspension warning message on the dash
  • Vehicle sitting low or leaning to one side
  • Air compressor running constantly
  • Other warning lamps may be on
  • Ride height and damping adjustments unavailable
  • Noticeable change in ride quality

Possible causes

  1. Failed suspension control module
  2. Open, shorted, or chafed CAN bus wiring
  3. Corroded connectors or terminals at the module
  4. Missing power or poor ground at the module (fuse, relay)
  5. Another faulty module loading down the CAN bus
  6. Height sensor fault affecting module operation
  7. Low battery voltage causing modules to drop offline

How to diagnose

  1. Run a full-system scan to see which modules are not communicating
  2. Look for other U-codes to tell a bus problem from a single-module failure
  3. Check the fuses and relays that power the suspension module
  4. Test battery voltage and charging system output
  5. Inspect the module's connector and harness for corrosion, moisture, and chafing
  6. Measure power and ground at the module connector
  7. Check CAN bus resistance (about 60 ohms between CAN-H and CAN-L) and voltages at the diagnostic connector
  8. Unplug suspect modules one at a time only when following a documented procedure

Common fixes

  • Repair damaged CAN bus or module power wiring
  • Clean or replace corroded connectors and terminals
  • Fix the power or ground circuit, replace the blown fuse or relay
  • Replace the suspension control module and code or adapt it to the vehicle
  • Replace any other module that is disrupting the bus
  • Check and calibrate the ride height sensors

Questions and answers

What does U0139 mean?

It means communication with the suspension control module has been lost. Other modules are not receiving its messages on the CAN bus, so suspension functions may be unavailable.

Can I drive with code U0139?

Usually yes, but carefully and only a short distance, such as to a shop. The suspension may be in a fallback mode, which affects ride height and handling.

Why is my air compressor running constantly with U0139?

Without communication, the system cannot properly monitor or control ride height. The compressor may run nonstop and overheat, so get it diagnosed promptly.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.