What it means
The ignition switch accessory-position circuit signal is above the expected limit. The code does not establish the switch state or resulting behavior.
At a glance
- Usually lights the check-engine light
How it works
The ignition switch sends an accessory-position signal to a receiving module when Accessory is selected. P2538 means the ACC signal is above its expected limit, which may occur if the ACC wire contacts battery voltage; the code alone does not say whether the key is in Accessory.
Common causes
Most likely first.
- ACC wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine or electrical-system warning light
- Accessories may remain powered with ignition off
- Accessory functions may behave inconsistently
How to diagnose it
- Save freeze-frame data and note whether the high ACC signal occurred with the key off, in Accessory, or in another position.
- Compare scan-tool accessory status with the key position and check whether accessories remain powered after shutdown.
- Inspect the ACC harness for a pinched wire against a battery-positive feed, damaged insulation, or corroded connector pins.
- Test the ACC circuit for a short to battery voltage and compare switch output with the manufacturer's specification.
- If the wiring is intact, verify the receiving module connector and input before considering a module fault.
Common fixes
- Repair or reroute a pinched ACC wire contacting a battery-positive source.
- Clean and secure corroded or loose ACC connector pins.
- Repair damaged wiring or a short between the accessory circuit and a supply wire.
- Replace a faulty ignition switch or repair the receiving module circuit only after testing confirms the cause.
Can I keep driving?
Accessories may remain powered with the ignition off and drain the battery. Confirm they switch off before leaving the vehicle, and avoid driving if an electrical fault affects essential equipment.
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.