What it means
Auxiliary ignition switch On/Start input reads stuck high — short to battery voltage. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The auxiliary ignition switch provides a Run/Start request from a second operating station to the controller. This code sets when the controller sees the On/Start input held high, typically because the signal wire is contacting battery voltage or the input is otherwise stuck active.
Common causes
Most likely first.
- Wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Auxiliary ignition or start function may be unavailable
How to diagnose it
- Use a scan tool to record freeze-frame data and check whether the auxiliary On/Start input remains active as the switch is turned off.
- Check whether the primary ignition works normally and whether the auxiliary station’s Run/Start function behaves unexpectedly.
- Inspect the auxiliary switch wiring and connectors for chafing, moisture, corrosion, pushed-back pins, or a signal wire pinched against a power feed.
- Following the wiring diagram and manufacturer’s procedure, test the input wire for a short to battery voltage and verify that the switch changes state correctly.
- If the switch and harness test normally, check the controller connector and input circuit for voltage where it should not be present.
Common fixes
- Repair the signal wire where it is contacting a battery-voltage feed.
- Clean or replace corroded, damaged, or pushed-back connector terminals in the auxiliary switch circuit.
- Replace a faulty auxiliary ignition switch if it holds the input high when disconnected from the harness.
- Repair the controller connector or input circuit if testing identifies an internal or terminal fault.
Can I keep driving?
The auxiliary ignition function may be unavailable or behave unpredictably, while the primary ignition may remain usable. Do not rely on the auxiliary station until the high input fault is corrected.
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.