OBD-II code family
Lost Communication With Gateway (U0146–U0150)
5 codes describing the same fault on 5 enumerated slots. The letter is the index your manufacturer assigned — it is not a physical difference, and it does not carry across makes.
What these codes mean
A gateway is the translator and traffic controller of a vehicle network. Modern vehicles run several separate buses — a fast one for powertrain and chassis, slower ones for body and comfort functions, and often dedicated links for infotainment and diagnostics. These buses use different speeds and sometimes different protocols, so they cannot talk to each other directly. The gateway sits between them, passing messages across, and it is usually also the point your scan tool actually connects to.
That central position is what makes this family of codes different from most communication faults. When an ordinary module goes quiet you lose that module's function. When a gateway goes quiet you can lose the ability to see anything on the far side of it, including modules that are perfectly healthy. A single gateway fault can therefore produce a screenful of Lost Communication codes from all over the vehicle — and chasing those individually is the classic way to waste a day. If you are looking at a long list of unrelated communication codes, suspect the thing they have in common before suspecting ten separate failures.
The letter — A through E — is the manufacturer's index for which gateway, on vehicles that have more than one. It has no generic meaning and no industry-standard mapping. Most vehicles have a single central gateway; multiple gateways appear on larger, more networked platforms where body, chassis and infotainment domains each get their own. Your wiring diagram is the only authority on which physical unit the letter refers to.
Diagnosis starts with power and ground at the gateway rather than with the network, because a module that has lost its supply looks exactly like a module that has failed. Check battery voltage first — low system voltage causes more spurious communication codes than any actual component failure. Then the connectors, then bus resistance, and only then the module itself. Gateways frequently require programming or security-linked setup when replaced, so this is rarely a straight swap.
Which communication with gateway is mine?
There is no generic answer, and any source that gives you one is guessing. The letter is assigned by the vehicle manufacturer, and the same letter refers to different physical components on different makes — sometimes on different model years of the same vehicle. The only authoritative source is the wiring diagram or service information for your exact year, make, model and body style.
A manufacturer-specific definition always outranks the generic one. If your make publishes its own meaning for this code, use that and ignore the generic description.