What it means
The ignition switch accessory-position circuit signal is below 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 the receiving module when the key or control is in Accessory. P2537 sets when the monitored ACC signal falls below its expected limit, such as from a short to ground or a resistive connector; it does not prove that accessory mode is selected.
Common causes
Most likely first.
- ACC wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check-engine or electrical-system warning light
- Radio or other accessory power may be unavailable
- Accessory functions may be inconsistent
How to diagnose it
- Record freeze-frame data and note the key position and accessory behavior when the low signal was detected.
- Compare scan-tool accessory status with the selected key position and check for related electrical faults.
- Inspect the ACC wire and connector pins for chafing to ground, corrosion, loose fit, or damage.
- Measure the ACC circuit and test for a short to ground or excessive resistance using the wiring diagram and manufacturer's specification.
- If the harness passes, test the ignition-switch accessory contact and the receiving module input.
Common fixes
- Clean and secure corroded or loose ACC connector pins.
- Repair chafed insulation or an ACC wire shorted to ground.
- Repair an open or high-resistance connection in the accessory circuit.
- Replace the ignition switch or repair the receiving module circuit only if testing isolates the fault there.
Can I keep driving?
The radio or other accessories may not work, though the engine may remain operable. Avoid relying on affected equipment, and check battery condition if accessory operation is intermittent.
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.