U0203: Lost Communication With Door Control Module E

What it means

Communication with Door Control Module E was not received as expected. The code does not identify which door or functions that module controls.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

Door Control Module E sends status and control messages to other modules over the vehicle network; E is a module identifier and does not specify which door it controls. U0203 is set when a monitoring module does not receive valid expected messages from Module E within its calibrated time.

Common causes

Most likely first.

1. Module unpowered
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Save freeze-frame information and scan all modules for communication codes to determine whether U0203 is isolated or part of a wider network interruption.
2. Check whether a capable scan tool can communicate directly with Door Control Module E and note whether other modules also list E as unavailable.
3. Locate Module E using vehicle-specific wiring information and inspect its connector, harness, and ground points for damage, corrosion, moisture, or a poor connection.
4. Test Module E’s power and ground under the manufacturer’s specified conditions before suspecting the module itself.
5. If its supplies are correct, check the associated CAN wiring and termination to specification, then investigate gateway routing if multiple modules are affected.

Common fixes

• Clean and secure a poor Module E connection or repair damaged wiring.
• Restore the module’s failed power or ground supply.
• Repair a CAN bus or termination fault confirmed by testing.
• Correct a gateway routing problem when broader network faults support that diagnosis.

Can I keep driving?

A vehicle with only door functions affected may be driven cautiously for a necessary short trip if it otherwise operates normally; those functions may not work until communication returns. Do not drive if other network faults affect steering, braking, visibility, or door security.