A damaged or corroded wiring harness in the flexible boot between the door and the body, where wires commonly flex and break.; A faulty door control module, often due to water intrusion or internal electronic failure.; Poor electrical connection at the door module connector, such as loose pins or corrosion.; A blown fuse or relay that supplies power to the door module, though this usually affects multiple doors.; A short or open in the communication bus wiring specific to that door, including a chafed wire against metal.; A failed body control module or gateway that cannot relay messages, but this typically sets additional communication codes.; Low battery voltage or a weak charging system causing intermittent module dropouts, especially on older vehicles.

DTC codes / U02xx · Lost communication with a control module / U020B

U020BLost Communication With Door Control Module H

Q: What does code U020B mean?

Lost Communication With Door Control Module H. U020B is a generic network communication code indicating that the module responsible for monitoring the vehicle's communication bus has lost contact with the door control module on the H circuit, which typically corresponds to a specific door such as the right rear. The computer sets this code when it expects regular status messages from that door module but does not receive them within the required time window, often due to a wiring fault, a failed module, or a power/ground issue.

U020B is a generic network communication code indicating that the module responsible for monitoring the vehicle's communication bus has lost contact with the door control module on the H circuit, which typically corresponds to a specific door such as the right rear. The computer sets this code when it expects regular status messages from that door module but does not receive them within the required time window, often due to a wiring fault, a failed module, or a power/ground issue.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaLost communication with a control module

Symptoms you may notice

The warning light on the dashboard, often the check engine light or a dedicated network fault indicator.
One or more doors may not respond to lock or unlock commands from the key fob or interior switches.
The affected door's window, mirror, or seat memory functions may become inoperative.
The door ajar warning may stay on or fail to illuminate when that door is opened.
Often no symptoms besides the warning light, especially if the door's basic functions still work through a backup path.
Intermittent operation of the door's electrical features, particularly over bumps or in wet weather.

Common causes, most likely first

A damaged or corroded wiring harness in the flexible boot between the door and the body, where wires commonly flex and break.
A faulty door control module, often due to water intrusion or internal electronic failure.
Poor electrical connection at the door module connector, such as loose pins or corrosion.
A blown fuse or relay that supplies power to the door module, though this usually affects multiple doors.
A short or open in the communication bus wiring specific to that door, including a chafed wire against metal.
A failed body control module or gateway that cannot relay messages, but this typically sets additional communication codes.
Low battery voltage or a weak charging system causing intermittent module dropouts, especially on older vehicles.

How to diagnose and fix it

Inspect the wiring harness in the door jamb boot for chafing, broken wires, or corrosion, and repair as needed.
Check the door module connector for tightness, corrosion, and proper pin fit, cleaning or replacing terminals if necessary.
Verify battery voltage and charging system output, as low voltage can cause communication faults.
Test for power and ground at the door module connector with a multimeter or test light, following the manufacturer's wiring diagram.
Use a scan tool to check for communication with the door module and perform a network integrity test if supported.
If wiring and power are good, substitute a known-good door module or perform a module swap to confirm the fault.
After repairs, clear the code and verify that communication is restored and the code does not return after a test drive.

Door jamb wiring fails more than modules

The flexible rubber boot between the door and body is the most common failure point because repeated door opening and closing fatigues the wires inside, often causing intermittent faults before a complete break.
A door control module that appears dead may simply have a poor ground connection at the door hinge or pillar, so always check ground points before condemning the module.
This code can be set by a completely different module on the network if it cannot relay messages, so look for other communication codes that might point to a shared bus fault.
Water leaks from a failed window seal or clogged sunroof drain can corrode the door module or its connectors, leading to U020B without any obvious wiring damage.
Some vehicles use the door module as a gateway for other components, so a failure can cause unrelated symptoms like a dead radio or inoperative interior lights.

Can I keep driving with U020B?

You can usually continue driving safely because the fault mainly affects convenience features, but avoid relying on the affected door's electrical functions and have the issue diagnosed soon to prevent a complete failure or battery drain. If multiple doors or safety systems are affected, seek professional diagnosis promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.