P2537 – Ignition Switch Accessory Position Circuit Low

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit Low

Definition source: SAE J2012/J2012DA (industry standard)

DTC P2537 indicates the powertrain control module has detected an abnormally low signal on the ignition switch accessory (ACC) position circuit. In normal operation, this circuit communicates the driver’s key/button position so modules can enable accessory power and coordinate wake-up, shutdown, and retained accessory power behaviors. A “circuit low” result is an electrical condition (low input) and does not, by itself, confirm a failed ignition switch. DTC behavior, monitored conditions, and which modules participate can vary by vehicle, so confirm the exact circuit description, connector views, and test points using the appropriate service information before testing or replacing parts.

What Does P2537 Mean?

P2537 – Ignition Switch Accessory Position Circuit Low means the control module has determined the accessory-position circuit from the ignition switch (or equivalent input device) is reporting a lower-than-expected electrical signal. Per SAE J2012 DTC structure conventions, this code identifies a specific monitored circuit and a “low input” fault type. In practice, the module is seeing the ACC signal pulled toward ground, dropped by excessive resistance, or missing its expected feed when the circuit should indicate a valid accessory state. The code is describing the electrical condition the module detected, not a guaranteed component failure.

Quick Reference

• Subsystem: Ignition switch accessory (ACC) position input circuit to the powertrain control module (and related networked modules, varies by vehicle).
• Common triggers: ACC signal short-to-ground, open power/feed to the ACC sense circuit, excessive resistance causing signal drop, poor terminal contact, or a mismatched ignition-position status.
• Likely root-cause buckets: Wiring/connector faults, ignition switch or keyless-start input device issues (as applicable), power/ground distribution problems, module input/driver concerns (less common).
• Severity: Typically moderate; may affect accessory power management, module wake/sleep behavior, and in some cases starting authorization logic depending on design.
• First checks: Verify battery health and grounds, check for related ignition/voltage DTCs, inspect ignition-switch/column connectors, and look for harness damage near moving parts.
• Common mistakes: Replacing the ignition switch first without confirming a circuit-low condition with testing or overlooking a shared ground/power issue affecting multiple inputs.

Theory of Operation

The ignition switch (or a start/stop control module, depending on vehicle design) provides discrete ignition-position signals such as OFF, ACC, RUN, and START. The accessory-position circuit is one of these signals and is monitored by the powertrain control module either directly (a dedicated input wire) or indirectly (a status message from another module). The monitored signal is expected to transition in a predictable way as the ignition state changes, enabling accessories and coordinating module wake-up and shutdown timing.

For a “circuit low” fault, the module detects the ACC input is lower than expected for a given state or remains low when the system logic expects it to be valid. Common electrical reasons include a short-to-ground, an open feed to the sense circuit, high resistance at a connector/terminal causing a voltage drop, or a shared ground/power issue pulling multiple ignition-position inputs down.

Symptoms

• Accessory power: Accessories may not power on in ACC or may shut off unexpectedly.
• Intermittent operation: Symptoms may come and go with vibration, steering column movement, or temperature changes.
• Starting behavior: Start enable/authorization may be inconsistent on some designs, potentially leading to a no-start or delayed start.
• Warning indicators: A malfunction indicator lamp or related warning message may illuminate depending on platform strategy.
• Retained power: Retained accessory power may not function correctly or may time out incorrectly.
• Electrical anomalies: Other ignition-position or power management faults may appear if the issue involves shared feeds or grounds.

Common Causes

• Open circuit or high resistance in the ignition switch accessory (ACC) signal wire between the ignition switch and the monitoring module
• Short-to-ground on the ACC signal circuit causing the module to see a persistently low input
• Poor connector contact at the ignition switch or at the module (backed-out terminal, corrosion, contamination, damaged lock, poor pin fit)
• Shared power feed issue to the ignition switch (open fuse link, failing fuse contact, damaged splice) reducing or removing the ACC output
• Ground-side issues in related switch/module circuits that create an unintended low reading (missing ground, high resistance ground path)
• Ignition switch internal wear or damage causing low/no ACC output under load
• Harness damage near the steering column or pass-through points (chafing, pinch, strain) intermittently pulling the ACC circuit low
• Module input fault or calibration/logic issue (less common; confirm circuit integrity first)

Diagnosis Steps

Tools typically needed include a scan tool capable of reading live data and freeze-frame information, a digital multimeter, and basic back-probing or terminal test tools. Depending on access, you may also need a wiring diagram/service information for connector pinouts and circuit routing (varies by vehicle), plus supplies for connector inspection and repair.

1. Confirm the DTC is present and current. Record freeze-frame and any companion DTCs, especially other ignition switch, power supply, or communication codes that could affect the accessory position circuit.
2. Review service information for the exact circuit name, connector pin IDs, and the module that monitors the accessory position input (varies by vehicle). Identify whether the input is a discrete ACC signal, an encoded switch input, or routed through an intermediate module.
3. Using live data, monitor the ignition/ACC-related PIDs while moving the key or switch through OFF/ACC/RUN/START (as applicable). Look for an ACC status that stays inactive/low when ACC is selected, flickers, or drops out under light load.
4. Perform a focused visual inspection at the ignition switch area and along the harness routing: look for rubbed-through insulation, pinched wiring, loose connectors, damaged connector locks, or signs of terminal spread. Correct any obvious mechanical issues before deeper electrical tests.
5. Do a wiggle test while observing the scan tool PID and/or multimeter readings: gently move the ignition switch connector, nearby harness sections, and any inline connectors or junctions. If the PID changes or the fault toggles, isolate the exact section that is movement-sensitive.
6. Check for a short-to-ground on the accessory position signal circuit. With the circuit safely isolated per service information (to avoid backfeeding modules), verify the signal conductor is not unintentionally connected to ground. If it is, locate the chafe/pinch point and repair the harness.
7. Check for an open circuit/high resistance on the accessory position signal circuit. With connectors unplugged as directed by service information, perform continuity checks end-to-end and verify there is no excessive resistance. Pay special attention to splices and areas with prior repairs.
8. Verify the ignition switch ACC output is present and stable when ACC is selected. Measure at the ignition switch side and compare to the module side to determine whether the problem is at the source (switch) or in the wiring/connector path.
9. Perform voltage-drop testing across suspect connectors and along the signal feed path while the circuit is loaded (as applicable by design). A low-input DTC can be caused by resistance that pulls the observed signal low; voltage-drop testing helps reveal poor contacts that may pass simple continuity checks.
10. If the circuit tests good and the ACC output is correct at the module input, confirm module grounds and power feeds are healthy using voltage-drop methods. Only after verifying wiring integrity and power/ground quality should a module input fault be considered.
11. Clear codes and perform a verification drive/functional test. Recheck for pending codes and confirm the ACC status PID behaves consistently through multiple key/switch cycles and with typical accessory loads applied.

Professional tip: If the symptom is intermittent, log live data for the accessory position input while duplicating the conditions that trigger the fault (key cycling, steering column tilt/telescope movement if equipped, vibration, and accessory load changes). Correlating a sudden “low” transition with harness movement or connector disturbance is often the fastest way to pinpoint a high-resistance terminal or chafed section without unnecessary parts replacement.

Possible Fixes & Repair Costs

Repair costs for P2537 vary widely because the root cause can range from a simple wiring issue to a switch or module input problem. Total cost depends on diagnostic time, parts replaced (if any), labor access to the steering column/dash, and verification testing afterward.

• Repair or replace damaged wiring in the ignition switch accessory (ACC) position circuit after confirming a circuit low condition
• Clean, re-seat, and secure related connectors; correct loose terminal fit, corrosion, or backed-out pins found during inspection and wiggle testing
• Restore proper power feed(s) and ground(s) required for accurate accessory-position sensing (repair opens, poor grounds, or excessive resistance)
• Replace the ignition switch or the accessory-position sensing component if testing confirms it cannot produce the required signal state
• Repair a short-to-ground in the accessory-position signal line or related harness routing points if confirmed with isolation testing
• Repair/replace the affected control module input circuit only after all external circuit and switch checks pass and the low-input condition is repeatable

Can I Still Drive With P2537?

You may be able to drive with P2537, but it depends on how the vehicle uses the ignition switch accessory-position signal. If you have no-start, intermittent stalling, loss of electrical accessories, warning messages, or any steering/brake assist concerns, do not drive; diagnose and repair first. If symptoms are mild, limit driving and avoid long trips until the circuit-low condition is verified and corrected, since the fault can become intermittent and worsen without warning.

What Happens If You Ignore P2537?

Ignoring P2537 can lead to intermittent accessory power operation, unpredictable electrical behavior tied to ignition key positions, repeated warning lights, and potential starting or shut-down related issues depending on vehicle design. A persistent circuit-low condition can also mask other electrical problems and may increase the chance of a no-start event or loss of accessory functions at an inconvenient time.

Last updated: February 21, 2026

Vehicles Commonly Affected by P2537

• Vehicles with an ignition switch that provides a discrete accessory-position signal to a control module
• Vehicles using a multi-circuit ignition switch with separate feeds for ACC, RUN, and START
• Vehicles with networked body/powertrain modules that share ignition-position status between modules
• Vehicles with high accessory electrical loads and frequent key cycling that can stress switch contacts or connectors
• Vehicles with steering column harness routing that is prone to movement-related wear or intermittent contact
• Vehicles with prior dash/steering column service where connectors may be left partially seated or terminals disturbed
• Vehicles operated in environments that promote connector corrosion or moisture intrusion (varies by vehicle design and sealing)
• Vehicles with aftermarket electrical add-ons tied into ignition/accessory circuits (installation quality varies)

After repairs, clear the DTC and confirm the fix by repeating the same key-position transitions and verifying the accessory-position input no longer reads low under the conditions that originally set P2537.