U302F: Ignition Output Accessory

What it means

Fault on the ignition ACC (accessory) output. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The ignition accessory (ACC) output supplies the vehicle circuits that operate in accessory mode, such as selected cabin electronics. The control module monitors the ACC output and its related communication; this code sets when the output or its reported status is faulty or unavailable.

Common causes

Most likely first.

1. Wiring or relay fault
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules for communication codes and note which accessory functions stopped working, since a cluster of faults can point to a shared ACC supply.
2. Check freeze-frame and available live data for ignition state and ACC output status when the fault occurred.
3. Inspect the ACC wiring, connectors, fuses, and relay for looseness, corrosion, heat damage, or a broken wire.
4. Check whether the ACC output changes as expected between ignition states, comparing the measurement with the manufacturer's specification.
5. If the supply and wiring check out, have the gateway routing and CAN network checked for message errors and termination outside the manufacturer's specification.

Common fixes

• Repair a loose, corroded, or damaged ACC-output connection.
• Replace a failed ACC relay or fuse after checking for the cause of failure.
• Repair damaged wiring in the ACC output circuit.
• Correct gateway configuration or repair a CAN network termination fault if testing confirms it.

Can I keep driving?

If the vehicle starts and drives normally and only accessory features are affected, limit use to a short trip for diagnosis. Avoid relying on affected electronics, and stop if essential visibility or safety functions fail.