P2538
Ignition Switch Accessory Position Circuit High
The ACC input reads stuck high — short to battery voltage. The ECM cannot detect when the operator releases the switch from ACC, accessory power timeouts do not work.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- ACC wire shorted to battery voltageCommon
- Connector pins corroded - high contact resistanceLess likely
- Supply wire pinched against B+ sourceLess likely
Parts involved
- Ignition Switch
- Wiring Harness
P2538 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.