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U0147 — Lost Communication Serial Data Gateway Module B

Generic OBD-II · all makesNetwork / communication

Code U0147 indicates that the vehicle's network has lost communication with the Serial Data Gateway Module 'B'. This module acts as a bridge between different communication buses, and its failure can disrupt data sharing among multiple control modules, leading to various drivability and functionality issues.

Symptoms

What causes it — most likely first

1. Faulty Serial Data Gateway Module B

Internal failure of the gateway module is the most common cause, often due to heat, vibration, or manufacturing defects.

2. Open or short in power or ground circuit to the gateway module

A blown fuse, broken wire, or corroded ground connection can prevent the module from powering up, leading to a loss of communication.

3. Damaged CAN bus wiring or connectors

Shorts to power/ground, open circuits, or high resistance in the communication lines can interrupt data transfer between the gateway and other modules.

4. Poor electrical connections at the gateway module

Loose, corroded, or backed-out terminals in the module connector can cause intermittent or complete loss of communication.

5. Faulty module on the same bus network

A shorted or malfunctioning module elsewhere on the bus can pull down the entire network, making the gateway module appear offline.

6. PCM failure (rare)

In very rare cases, an internal fault in the PCM can disrupt bus communication, but this is seldom the root cause for U0147.

How it's diagnosed

  1. Scan all modules for communication codes; note which modules are not responding to identify the affected bus.
  2. Visually inspect the gateway module connector and wiring for corrosion, bent pins, or loose connections.
  3. Check power and ground at the gateway module using a digital multimeter; verify battery voltage and ground continuity.
  4. Test the CAN bus wiring for opens, shorts, or incorrect resistance (typically 60 ohms across the bus with modules disconnected).
  5. If wiring and power/ground are good, disconnect the gateway module and check if communication is restored to other modules; if so, replace the gateway module.
  6. As a last resort, isolate other modules on the same bus to identify a potential faulty module pulling down the network.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make

Frequently asked

What is the Serial Data Gateway Module B?

It is an electronic module that translates data between different communication networks in the vehicle, such as high-speed and low-speed CAN buses, allowing modules on different networks to share information.

Can I drive with a U0147 code?

It is not recommended. The code can cause drivability issues, warning lights, and may affect critical systems like engine management or safety features. The vehicle should be diagnosed and repaired promptly.

Is the PCM the most likely cause of U0147?

No. Despite some online suggestions, the PCM is rarely the cause. The gateway module itself, its power/ground circuits, or CAN bus wiring are far more common culprits. Replacing the PCM without proper diagnosis is usually a misstep.

Can I replace the gateway module myself?

Replacement may require programming or configuration with a professional scan tool to match the vehicle's network. Without proper setup, the module may not function, so professional assistance is often necessary.