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U0139 — Lost Communication Suspension Control Module B

Generic OBD-II · all makesNetwork / communication

U0139 indicates that the Powertrain Control Module (PCM) has lost communication with Suspension Control Module B. This communication loss prevents the PCM from receiving suspension data needed for vehicle stability and ride control.

Symptoms

What causes it — most likely first

1. Faulty Suspension Control Module B

The module itself may have failed internal circuitry or a damaged processor, breaking the communication link.

2. Wiring or connector problems between PCM and Module B

Corroded pins, broken wires, or loose connectors can interrupt the CAN bus signal.

3. Damaged CAN bus network segment

A short or open circuit in the vehicle’s CAN high/low lines affecting the path to Module B.

4. PCM communication port failure

A malfunctioning PCM communication transceiver can prevent it from receiving data, though this is less common.

5. Software glitch in PCM or Module B

Rarely, a corrupted calibration file or outdated software can cause intermittent loss of communication.

How it's diagnosed

  1. Scan for additional codes and verify that the communication error is isolated to U0139.
  2. Inspect wiring harness and connectors between PCM and Suspension Control Module B for damage, corrosion, or looseness.
  3. Perform a continuity and resistance check on the CAN high and CAN low wires for the affected segment.
  4. Use a CAN bus analyzer or oscilloscope to monitor live traffic and confirm whether the PCM is sending/receiving messages.
  5. If wiring is sound and bus signals are present, test or replace Suspension Control Module B.
  6. Only after confirming module and wiring integrity should PCM communication hardware be evaluated.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0130 — Lost Communication Steering Effort ConU0131 — Lost Communication Power Steering ContU0132 — Lost Communication Suspension Control U0133 — Lost Communication Active Roll ControlU0134 — Lost Communication Power Steering ContU0135 — Lost Communication Differential Contro

Frequently asked

Do I need to replace the PCM to fix U0139?

In most cases the PCM is not at fault. Replacing the PCM is rarely needed and is usually not the correct repair.

Can a blown fuse cause this code?

Yes, a fuse that powers the CAN bus or the suspension module can open the communication path and trigger U0139.

Will the code disappear after a battery disconnect?

A simple reset may clear the code temporarily, but if the underlying fault remains, the code will return.

Is this code related to the vehicle’s ride‑height adjustment feature?

Yes, loss of communication with Suspension Control Module B can prevent the ride‑height system from operating correctly.