U0147

Lost Communication With Gateway B

U0147 is a generic OBD-II network diagnostic trouble code: Lost Communication With Gateway B. It is logged by the engine control unit when the network monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
U0147
Group
Network
System
Network
Severity
Warning (MIL on)
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What U0147 means

U0147 is a network communication fault that sets when a control module -- typically the ECM, PCM, or the vehicle's primary gateway -- stops receiving expected serial data messages from the module designated Gateway 'B'. A gateway is a routing node that bridges the vehicle's separate data buses, for example passing information between a high-speed powertrain CAN and a lower-speed body or comfort CAN. When two or more gateway nodes exist, they are labelled A, B, and so on; the 'B' suffix identifies the second such node in the manufacturer's topology.

Because the gateway relays traffic between networks, losing communication with it can produce widely varied symptoms. Modules that depend on data routed through Gateway 'B' may report their own lost-communication codes, and some vehicles display a 'NO BUS' message on the instrument cluster. Low system voltage is a very common trigger, because a weak battery lets modules reset or drop offline during cranking.

Diagnosis should begin by reading all stored codes and freeze-frame data, then confirming battery and charging health. Verify power and ground at the gateway, inspect the bus wiring and connectors for damage or corrosion, and measure CAN termination resistance before considering module replacement. A replacement gateway usually requires programming to the vehicle.

Common causes

Most-frequently reported root causes when U0147 is logged.

  • 1
    Weak or discharged battery causing modules to drop offline during cranking.
  • 2
    Open circuit in the CAN bus wiring to or from the Gateway 'B' module.
  • 3
    Short to ground or short to voltage on the bus segment served by the gateway.
  • 4
    Corroded, loose, or backed-out terminal at the gateway connector.
  • 5
    Missing or intermittent power or ground supply to the gateway module.
  • 6
    Internal hardware failure of the Gateway 'B' module.
  • 7
    Gateway module not programmed or configured after replacement.

Symptoms drivers notice

MIL or a network warning indicator illuminated.
Instrument cluster may display a 'NO BUS' or communication error message.
Multiple additional U-codes stored by modules that route data through the gateway.
Intermittent operation of features that depend on cross-bus data.
Hard-to-reproduce faults that appear after cold starts or low-voltage events.

How to diagnose U0147

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and freeze-frame data; note any companion U-codes indicating a wider bus fault.
  2. 2
    Test and load the battery and verify charging voltage before further diagnosis.
  3. 3
    Identify the Gateway 'B' module location and its bus assignments from the vehicle service manual.
  4. 4
    Measure supply voltage and ground at the gateway connector with the ignition on.
  5. 5
    Inspect the gateway harness and connectors for damage, corrosion, or moisture intrusion.
  6. 6
    Measure CAN bus termination resistance on the affected segment to confirm bus integrity.
  7. 7
    If wiring and power are confirmed good and the module is absent from the bus, replace and program the gateway per the manufacturer procedure.

Related network codes

Frequently asked questions

What does the Gateway 'B' module do?

A gateway routes and translates data between the vehicle's separate communication buses. The 'B' designation identifies the second gateway node in the manufacturer's network topology; consult the service manual for its exact bus assignments.

Can a weak battery cause U0147?

Yes. Low voltage during cranking is one of the most common causes of network communication codes, because modules can reset or drop off the bus. Always test the battery and charging system first.

Why do I see several U-codes with U0147?

Because the gateway relays traffic between buses, a gateway fault can prevent many modules from exchanging data, so each affected module may log its own lost-communication code.

Does a replacement gateway need programming?

On most vehicles yes. A new gateway that has not been configured to the vehicle may not communicate correctly, leaving U0147 set even though the hardware is sound.

Disabling U0147 in software

RaceTune can permanently disable U0147 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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