U008C: Vehicle Communication Bus G (+) Low

What it means

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

How it works

Bus G is a vehicle network that lets connected control modules exchange messages over its positive and negative conductors. A module sets U008C when it detects the bus G positive conductor at a lower level than expected, which can disrupt communication on that network.

Common causes

Most likely first.

1. Short to ground 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 note which modules are missing, since that can help identify the affected network segment.
2. Review freeze-frame or event data and live network status for when the low condition and communication losses occur.
3. With the vehicle powered down as specified by the manufacturer, inspect bus G positive wiring and connectors for pinched insulation, corrosion, looseness, or contact with ground.
4. Check the bus G positive conductor for a short to ground and test continuity through suspect sections using the manufacturer's procedure.
5. If the wiring and connectors pass, isolate modules or the gateway on bus G using the manufacturer's diagnostic procedure to find a unit pulling the positive line low.

Common fixes

• Clean and secure a loose or corroded bus G connector.
• Repair damaged bus G positive wiring or insulation that is shorting to ground.
• Repair or replace a faulty connector or terminal on the bus G positive circuit.
• Repair or replace a module or gateway shown by testing to be pulling bus G positive low.

Can I keep driving?

Driving may be possible if affected functions are not safety-critical, but bus G dependent features can stop working or warning messages may appear. Avoid driving if the fault affects steering, braking, restraint, or other essential systems.