Open circuit or high resistance in the bus H wiring, including a broken wire, corroded terminal, or damaged connector; Short to ground or short to voltage on one of the bus H conductors, often from chafed insulation or water intrusion; A failed control module on bus H that is dragging the bus down or no longer transmitting; Loose or corroded ground connection shared by modules on the bus, causing communication dropout; Low battery voltage or a failing charging system that causes modules to reset and lose bus communication; Aftermarket accessories improperly tapped into the bus wiring, introducing noise or a short; Internal fault in the gateway module that routes messages between buses, isolating bus H

DTC codes / U00xx · Network wiring and bus faults / U007A

U007AControl Module Communication Bus H Off

Q: What does code U007A mean?

Control Module Communication Bus H Off. U007A is a generic network communication code indicating that a control module has lost communication on the dedicated bus designated 'H', which is a secondary or supplemental data bus used for specific module-to-module traffic. The detecting module has logged that it can no longer send or receive messages on that bus, often because the bus wiring is open, shorted, or a module on that bus has failed.

U007A is a generic network communication code indicating that a control module has lost communication on the dedicated bus designated 'H', which is a secondary or supplemental data bus used for specific module-to-module traffic. The detecting module has logged that it can no longer send or receive messages on that bus, often because the bus wiring is open, shorted, or a module on that bus has failed.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaNetwork wiring and bus faults

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) or a communication fault message on the dashboard
Multiple unrelated warning lights appearing at once because several modules share the affected bus
Intermittent or complete failure of features controlled by modules on bus H, such as memory seats, door modules, or trailer brake controllers
The scan tool may fail to communicate with one or more modules during a health check
Often no symptoms besides the warning light if the affected bus only carries non-critical convenience data
Unexpected electrical gremlins such as modules waking up randomly or accessories not responding

Common causes, most likely first

Open circuit or high resistance in the bus H wiring, including a broken wire, corroded terminal, or damaged connector
Short to ground or short to voltage on one of the bus H conductors, often from chafed insulation or water intrusion
A failed control module on bus H that is dragging the bus down or no longer transmitting
Loose or corroded ground connection shared by modules on the bus, causing communication dropout
Low battery voltage or a failing charging system that causes modules to reset and lose bus communication
Aftermarket accessories improperly tapped into the bus wiring, introducing noise or a short
Internal fault in the gateway module that routes messages between buses, isolating bus H

How to diagnose and fix it

Perform a full scan of all modules and record which modules are online and which are missing from the bus H network
Check battery voltage and charging system output, as low voltage is a common cause of spurious communication codes
Inspect the bus H wiring harness and connectors for chafing, corrosion, water intrusion, and loose pins, especially near body seams and module connectors
Measure resistance on the bus H CAN (controller area network) lines with the battery disconnected to check for opens or shorts, comparing to manufacturer specifications
Disconnect modules one at a time from bus H to see if communication is restored, isolating a faulty module that is shorting the bus
Repair or replace damaged wiring, terminals, or connectors, then clear the code and verify communication with all modules on bus H
If a module is confirmed faulty, replace or reprogram it according to the manufacturer's procedures and recheck for the code

Why bus H faults are often misdiagnosed

Bus H is frequently a secondary bus for body or convenience modules, so a failure may not affect drivability and the code can be ignored until a convenience feature stops working.
A single failed module on bus H can pull the entire bus down, making it look like a wiring fault when the real problem is the module itself.
Technicians often replace the module that set the code when the actual fault is a corroded connector or chafed wire elsewhere on the bus.
Aftermarket alarms, remote starters, or trailer wiring tapped into bus H are a common source of intermittent communication codes that only appear under certain conditions.
The code does not always mean the bus is dead; it can be set by a momentary glitch during a low-voltage event such as engine cranking or a weak battery.

Can I keep driving with U007A?

The vehicle is generally safe to drive if the code is the only symptom and the affected bus carries only convenience features, but avoid long trips until diagnosed because a failing bus can disable safety or body systems unpredictably. If multiple warning lights are on or the vehicle exhibits electrical oddities, have it inspected 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.