P2538 Ignition Switch Accessory Position Circuit High

P2538 is set when the accessory input reads high in a state where it should be inactive, for instance once the vehicle is switched off and the body module should have released the line. Backfeed from an aftermarket device, a stuck accessory relay or a wire touching a battery feed are the obvious causes. A permanently high accessory line can keep modules awake and drain the battery. No manufacturer publishes P2538; the documented counterpart is GM's P2537, judged on the accessory wake-up signal against propulsion status, and GM's PIT5308 notes that some voltage after key-off is normal while the body module is still awake, so timing matters before calling the line faulty. P2536 is the general and P2537 the low fault.

Likely causes

Symptoms

• Battery drain while parked
• Radio or accessories stay on after key-off

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com.