CAN network

U0240 — Lost Communication with Seat Control Module A

Severity: low Safe to drive

What U0240 means

U0240 means one or more control modules stopped receiving messages from Seat Control Module A, which usually handles the power seat and memory positions. Vehicle modules share data over the CAN bus, so when one goes silent the others log a lost-communication code. The cause may be the module itself, its power or ground supply, or damaged bus wiring.

Symptoms

  • Power seat does not move
  • Memory seat positions are lost
  • Other warning lamps may be on
  • Functions handled by the module are unavailable
  • Other U-code communication faults stored at the same time

Possible causes

  1. Failed seat control module
  2. Damaged harness under the seat (pinched or chafed)
  3. Liquid spilled on switches or the module
  4. CAN bus wiring fault: open, short, or chafed harness
  5. Another faulty module loading the bus
  6. Corroded connectors or terminals
  7. Power supply or ground fault at the module

How to diagnose

  1. Run a full-vehicle scan to see which modules do not respond
  2. Look for other lost-communication codes to tell a single-module fault from a bus-wide problem
  3. Inspect the harness and connectors under the seat for pinching, corrosion, or moisture
  4. Check the fuses, power feed, and ground of the seat module
  5. Measure CAN bus resistance and voltages at the diagnostic connector
  6. Test the CAN-H and CAN-L lines to the module for opens and shorts
  7. Disconnect suspect modules one at a time, only following the documented manufacturer procedure

Common fixes

  • Repair or replace the damaged section of harness
  • Clean or replace corroded connectors and terminals
  • Restore the module's power and ground supply
  • Dry and clean the module and switches after a spill, or replace them if damaged
  • Replace the faulty seat module and program or code it to the vehicle

Questions and answers

Can I drive with a U0240 code?

Usually yes. It relates to a comfort feature and does not affect the engine or brakes. Make sure the seat is in a safe position and have it diagnosed soon.

Why did my memory seat stop working?

The seat module is not communicating on the bus, so stored positions are unavailable. The usual culprits are module power, the harness under the seat, or the module itself.

What should I check first?

Inspect the harness and connectors under the seat, then check the fuses, power, and ground of the module. These are the most common and cheapest fixes.

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.