A loose, corroded, or damaged electrical connector at Switch Input Module A or at the module it communicates with.; A blown fuse or poor ground connection that removes power from Switch Input Module A.; Wiring damage in the controller area network (CAN) bus or other data bus between the module and the rest of the vehicle.; A failed Switch Input Module A that no longer transmits on the network.; A faulty body control module or gateway that is not passing messages to or from Switch Input Module A.; Low battery voltage or a weak charging system causing modules to drop off the network intermittently.; Aftermarket accessories or poor previous repairs that disturb the data bus wiring or introduce electrical noise.

DTC codes / U01xx · Lost communication with a control module / U01B7

U01B7Lost Communication With Switch Input Module A

Q: What does code U01B7 mean?

Lost Communication With Switch Input Module A. U01B7 is a generic network communication code indicating that a control module on the vehicle's data bus has lost contact with the Switch Input Module A, which is the module that reads inputs from switches such as steering wheel buttons, console switches, or door-mounted controls. The computer detected that expected periodic messages from that module stopped arriving within the required time window, so it flagged the module as missing rather than reporting a faulty switch itself.

U01B7 is a generic network communication code indicating that a control module on the vehicle's data bus has lost contact with the Switch Input Module A, which is the module that reads inputs from switches such as steering wheel buttons, console switches, or door-mounted controls. The computer detected that expected periodic messages from that module stopped arriving within the required time window, so it flagged the module as missing rather than reporting a faulty switch itself.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaLost communication with a control module

Symptoms you may notice

The check engine light or a body control warning lamp illuminates on the dashboard.
Some or all of the switches handled by Switch Input Module A stop working, such as steering wheel audio or cruise buttons.
Other modules may show unrelated warning messages because they cannot share switch data across the network.
Intermittent operation of affected switches, especially over bumps or in wet weather, as the communication drops in and out.
Often no symptoms besides the warning light, because the module may still be powered and only its network messages are missing.

Common causes, most likely first

A loose, corroded, or damaged electrical connector at Switch Input Module A or at the module it communicates with.
A blown fuse or poor ground connection that removes power from Switch Input Module A.
Wiring damage in the controller area network (CAN) bus or other data bus between the module and the rest of the vehicle.
A failed Switch Input Module A that no longer transmits on the network.
A faulty body control module or gateway that is not passing messages to or from Switch Input Module A.
Low battery voltage or a weak charging system causing modules to drop off the network intermittently.
Aftermarket accessories or poor previous repairs that disturb the data bus wiring or introduce electrical noise.

How to diagnose and fix it

Verify battery voltage and charging system output, then clear the code and test-drive to see whether U01B7 returns immediately.
Inspect the connector and wiring at Switch Input Module A for corrosion, pushed pins, or chafed insulation, and check the module's fuse and ground.
Use a scan tool to check whether other modules can communicate with Switch Input Module A and whether the code is current or history.
Perform a voltage drop and resistance check on the data bus wires between Switch Input Module A and the gateway or body control module.
If wiring and power are good, substitute a known-good Switch Input Module A and recheck communication before condemning other modules.
Check for technical service bulletins or software updates for the body control module or gateway that address communication dropouts.
After repair, clear all codes and confirm that Switch Input Module A stays online through a full drive cycle with all accessories operated.

What a missing switch module really means

U01B7 rarely means a switch itself has failed; the code is set because the module that reads the switches is not talking on the network, so replacing buttons is usually wasted money.
A common missed cause is a partially seated connector at the module after interior work, a stereo install, or a windshield replacement that disturbed dash wiring.
The same code can appear when a body control module or gateway is failing to route messages, so the fault may live in a different module than the one named in the definition.
Low voltage from an aging battery can make modules drop offline intermittently and set U01B7 without any hard wiring fault, so always load-test the battery first.
Some vehicles set this code after a module is disconnected during service and never clear it until a full network recheck is performed, so a stored history code is not proof of a live fault.

Can I keep driving with U01B7?

The vehicle is generally safe to drive because the fault affects switch communication rather than engine or brake control, but do not ignore it if steering wheel or safety-related switches stop working. Avoid long trips until the cause is found, and have the network fault diagnosed promptly if multiple warning lights appear.

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.