What it means
Communication with Door Control Module H 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 H exchanges door-related status and control messages with other modules over the vehicle network; H is a module identifier and does not name a particular door. U020B sets when expected valid messages from Module H are missing for the calibrated monitoring period.
Common causes
Most likely first.
- Module unpowered
- Gateway module routing CAN messages incorrectly
- 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
- Save freeze-frame data and scan the full vehicle for communication faults to see whether U020B is isolated or part of a network-wide issue.
- Check with a capable scan tool whether Door Control Module H responds and which other modules report it as missing.
- Locate Module H using vehicle-specific wiring information and inspect its connector, harness, and grounds for water, corrosion, damage, or poor contact.
- Test the module’s power and ground circuits under the manufacturer’s specified conditions.
- If power and ground are sound, test the CAN wiring and termination to specification and investigate gateway routing if multiple modules are offline.
Common fixes
- Repair a loose or damaged Module H connector or harness and remove corrosion where appropriate.
- Restore a failed power or ground supply to Door Control Module H.
- Repair CAN wiring or termination faults identified by testing.
- Correct gateway routing when broader communication faults confirm that direction.
Can I keep driving?
If only door features are affected and the vehicle remains safe to operate, limit driving to necessary trips and confirm the doors are securely latched. Stop if other network faults affect safe vehicle control, visibility, or access.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.