U009A: Vehicle Communication Bus H (-) shorted to Bus H (+)

What it means

A fault is detected between the positive and negative conductors of vehicle communication bus H. Which functions are affected depends on the vehicle’s network design.

How it works

Bus H carries messages over separate positive and negative conductors between its connected modules. U009A is set when those two conductors are detected as connected to each other, which can distort the bus signal and interrupt communication.

Common causes

Most likely first.

1. Bus H conductors shorted together
2. Damaged or corroded connector
3. A module fault

Symptoms

• Communication faults in modules using bus H
• Warning lights or messages
• Functions relying on bus H may be unavailable

How to diagnose it

1. Scan for U009A and other bus H communication codes, and record which modules are affected and any event data.
2. Use the wiring diagram to locate both bus H conductors and inspect their shared routes and connectors for crushed insulation, corrosion, bent pins, or wiring repairs that could bridge them.
3. With power isolated as specified, test for unwanted continuity between bus H positive and negative.
4. Separate and test wiring sections and connectors according to the manufacturer's procedure to locate where the two conductors are touching.
5. If the wiring does not show a short, isolate connected modules or the gateway as directed to identify an internal module fault.

Common fixes

• Clean and secure a connector with corrosion or displaced pins bridging the conductors.
• Repair wiring where bus H positive and negative are shorted together.
• Repair or replace a module confirmed to be creating the conductor-to-conductor short.

Can I keep driving?

Avoid driving if the fault affects systems needed for safe vehicle control or if warning messages indicate those systems are unavailable. Otherwise, limit use until diagnosis, because a conductor short can interrupt communication for multiple bus H functions.