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U0093 — Vehicle Communication Bus H Performance

Generic OBD-II · all makesNetwork / communication

U0093 indicates a loss of communication on the high‑speed vehicle bus (H‑Performance) between the Powertrain Control Module and other network nodes. The PCM detects that messages are not being transmitted or received within the expected time frame.

Symptoms

What causes it — most likely first

1. Faulty or corroded high‑speed bus wiring/connectors

Broken conductors, loose pins, or corrosion in the CAN‑H (high‑speed) harness can interrupt message flow.

2. Failed bus termination resistor or improper termination

Missing or damaged 120 Ω termination at each end of the H‑Performance network can cause signal reflections and loss of communication.

3. Defective network node (e.g., transmission control module, ABS module)

A single module that is shorted, open, or internally failed can stall the entire bus.

4. Short to ground or voltage spike on the bus lines

Electrical shorts or transients from aftermarket accessories can disrupt the CAN‑H signal.

5. Powertrain Control Module (PCM) hardware failure

Rarely, the PCM’s CAN transceiver may be damaged, but this is usually a last‑resort diagnosis after all wiring and nodes are verified.

How it's diagnosed

  1. Visually inspect H‑Performance wiring and connectors for damage, corrosion, or looseness; repair as needed.
  2. Measure bus voltage on CAN‑H and CAN‑L lines with a scope or multimeter to confirm proper 2.5 V differential and termination resistance.
  3. Use a scan tool to isolate the network by disconnecting individual modules one at a time to see if the code clears.
  4. Check for shorts or voltage spikes on the bus lines with a diagnostic lamp or oscilloscope during engine start and operation.
  5. If all hardware checks are good, perform a PCM CAN‑transceiver test or reflash the PCM to rule out software glitches.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0090 — Vehicle Communication Bus G HighU0091 — Vehicle Communication Bus G Shorted U0092 — Vehicle Communication Bus HU0094 — Vehicle Communication Bus H OpenU0095 — Vehicle Communication Bus H LowU0096 — Vehicle Communication Bus H High

Frequently asked

Do I need to replace the PCM to fix a U0093 code?

In most cases no. The PCM is rarely the root cause; wiring, termination, or a faulty peripheral node are far more common. Replace the PCM only after every other possibility has been eliminated.

Can aftermarket accessories cause U0093?

Yes. Poorly shielded or incorrectly wired aftermarket devices can introduce noise or a short on the high‑speed bus, leading to communication loss.

Will clearing the code without fixing anything make it reappear?

Usually the code will return immediately if the underlying communication fault remains, because the PCM continuously monitors bus integrity.

Is a software update ever needed for this code?

Occasionally a manufacturer‑issued software update can resolve a known CAN‑bus timing issue, but this is less common than a physical hardware fault.