What it means
Fault on the ACC/ON/START ignition output line driven by the module. 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 ACC/ON/START output supplies ignition-state power to circuits that need accessory, on, or start operation. The module monitors this output for the expected state; this code indicates a fault on that line, which can interrupt power to dependent systems.
Common causes
Most likely first.
- Wiring or relay fault
- Gateway module routing CAN messages incorrectly
- 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
- Record all module codes and freeze-frame details, noting whether the fault occurs during accessory, ignition-on, or cranking.
- Use a scan tool to compare the commanded ACC/ON/START state with the status reported by the controlling module and affected modules.
- Inspect the output wiring, connectors, fuse connections, and related relay for looseness, heat damage, corrosion, or a broken wire.
- Test for the expected output and relay operation in each commanded key state, following the manufacturer's circuit procedure.
- If the output circuit passes, check gateway routing and CAN termination where communication faults are also present.
Common fixes
- Repair a damaged ignition-output wire or connector.
- Replace a confirmed faulty relay or fuse connection with the correct specified part.
- Correct a confirmed gateway routing or configuration fault.
- Repair a CAN termination fault if testing shows it is outside specification.
Can I keep driving?
Do not drive if the engine, lighting, steering, braking, or other essential systems lose power or behave unpredictably. If operation is normal, use caution because an ignition output fault can cause dependent circuits to cut out or prevent restart.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.