U01B7 code meaning
Lost Communication With Switch Input Module A
What U01B7 means
A switch input module collects a group of buttons, for instance in a door trim, steering wheel or centre console, and sends their states to other units as network messages instead of wiring every switch on its own. A patent by Eaton describes the idea: a central unit queries every switch by its address and accepts only answers whose address and state are valid. U01B7 is set when module A stops responding, so the receiver, often the body controller, treats its buttons as unknown. Which switches belong to module A is up to each carmaker; no manufacturer documents this code publicly. Typically a whole group of buttons does nothing and their indicator lamps stay dark, while all other systems keep working. U04BA is the invalid-data code; modules B and C have U01B8 and U01B9.
U01B7 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U01B7
- A group of buttons without function
- Switch backlight or indicator lamps dark
Common causes of U01B7
- Most likelyLoose connector or broken wire at the switch panel
- PossibleLiquid spilled into the switch module
- Less likelySwitch input module A faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Switch input module aCAN bus
What each part of U01B7 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B7 | The exact fault in that area. |
What to do next
- Note U01B7 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U01B7
What does U01B7 mean?
U01B7 means "Lost Communication With Switch Input Module A". A switch input module collects a group of buttons, for instance in a door trim, steering wheel or centre console, and sends their states to other units as network messages instead of wiring every switch on its own. It is a generic code, so it means the same on every make.
Is it safe to drive with U01B7?
U01B7 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U01B7 fail an emissions test?
U01B7 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U01B7 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U01B7 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.