U008D: Vehicle Communication Bus G (+) High

What it means

A fault is detected on the positive conductor of vehicle communication bus G; the code descriptor specifies a high condition. Which functions are affected depends on the vehicle’s network design.

How it works

Bus G carries messages between the control modules connected to that vehicle network. U008D is set when the bus G positive conductor is detected at a higher level than expected, often because it is contacting a voltage source and communication is being disturbed.

Common causes

Most likely first.

1. Short to voltage or damaged bus G positive wire
2. Loose or corroded connector
3. A module or gateway fault

Symptoms

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

How to diagnose it

1. Scan all modules for bus G communication codes and identify which modules have stopped responding.
2. Check freeze-frame or event data and live network status to see whether the high condition coincides with module dropouts.
3. With power isolated as directed by the manufacturer, inspect bus G positive wiring and connectors for chafing against powered wires, damaged insulation, corrosion, or poor pin contact.
4. Test the bus G positive conductor for a short to voltage and check continuity across suspect wiring and connectors against the manufacturer's procedure.
5. If no wiring fault is found, use the manufacturer's isolation procedure to determine whether a module or gateway is driving bus G positive high.

Common fixes

• Secure a loose bus G connector and clean corrosion from its terminals.
• Repair chafed or damaged bus G positive wiring that contacts a voltage source.
• Repair or replace damaged connector terminals on the bus G positive circuit.
• Repair or replace a module or gateway confirmed to be causing the high condition.

Can I keep driving?

The vehicle may remain drivable if bus G does not carry essential functions, but connected features can fail and warning messages may appear. Do not continue if the affected network controls a safety-critical system or its operation is uncertain.