14-05-2025
5 min.
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P2537 Ignition Switch Accessory Position Circuit Low

P2537 is a generic OBD-II diagnostic trouble code that indicates the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected that the Ignition Switch Accessory Position Circuit is operating with a voltage lower than the manufacturer-specified range.

In simple terms, the ECM or related control module is receiving a weak or insufficient electrical signal from the ignition switch when it is in the ACC (Accessory) position. This means the vehicle is not seeing the expected voltage level required to confirm that accessory power has been activated.

The Accessory position allows electrical systems to operate without starting the engine. These systems commonly include:

Radio and infotainment system
Power outlets
Interior electronics
Navigation systems
Some climate control functions
Comfort and convenience features

If the ACC circuit voltage drops below the expected value, the ECM stores diagnostic code P2537 and may activate the Check Engine Light or other electrical warnings.

What Does P2537 Mean?

The ignition switch typically has several positions:

OFF
ACCESSORY (ACC)
RUN (ON)
START

When the ignition switch is placed in the ACC position, the vehicle expects a specific voltage signal to confirm that accessory power should be supplied.

The vehicle's control modules monitor the ACC circuit to determine:

When accessory systems should be powered.
When modules should wake up.
When battery-saving functions should activate.
How electrical loads should be managed.

If the ACC signal voltage is lower than expected, the system identifies a low-voltage condition and stores code P2537.

Unlike P2536, which indicates a general ACC circuit malfunction, and P2538, which indicates a high-voltage condition, P2537 specifically identifies a low electrical signal in the Accessory Position Circuit.

Common Symptoms of P2537

Symptoms may vary depending on which systems depend on the ACC circuit.

Common symptoms include:

Check Engine Light illuminated
Radio does not turn on
Infotainment system resets
Power outlets do not work
Interior electronics operate intermittently
Dashboard display resets
Navigation system problems
Accessory power shuts off unexpectedly
Battery management system warnings
Push-button start issues
Additional ignition switch or BCM-related fault codes

In some cases, the vehicle may start and drive normally because the ACC circuit is separate from the main RUN circuit.

Common Causes of P2537

Several electrical problems can cause low voltage in the accessory circuit.

Faulty ignition switch

Internal contacts may wear out and create high resistance, reducing ACC voltage.

Weak battery

Low battery voltage can affect accessory circuit operation.

Poor battery connections

Corroded or loose battery terminals can reduce available electrical power.

Damaged ACC wiring

The accessory circuit wiring may develop:

Broken wires
Open circuits
Chafed insulation
Heat damage
Corrosion

Loose or corroded electrical connectors

Poor terminal contact can reduce voltage reaching the control module.

Faulty accessory relay

A failing relay may not provide sufficient voltage to accessory circuits.

Blown fuse or poor fuse connection

A damaged fuse or fuse holder may create a voltage drop.

Poor ground connection

A weak ground can cause low voltage readings.

Faulty Body Control Module (BCM)

The BCM often controls accessory power distribution in modern vehicles.

CAN bus communication problems

Communication failures may prevent correct ACC status recognition.

Aftermarket electrical accessories

Incorrect installation of:

Audio systems
Alarm systems
Remote starters
Additional electronic devices

can interfere with accessory power circuits.

ECM malfunction

Although uncommon, an internal ECM fault may incorrectly detect a low ACC voltage condition.

Vehicles Commonly Affected by P2537

P2537 can occur on many OBD-II vehicles equipped with electronically controlled ignition systems.

Frequently affected vehicles include:

Ford F-150
Ford Explorer
Ford Transit
Chevrolet Silverado
Chevrolet Equinox
GMC Sierra
Ram 1500
Jeep Grand Cherokee
Toyota Camry
Toyota Corolla
Honda Accord
Honda Civic
Nissan Altima
Nissan Rogue
Hyundai Elantra
Kia Sportage
BMW 3 Series
Mercedes-Benz C-Class
Audi A4
Volkswagen Golf
Subaru Forester

Vehicles with keyless entry and push-button start systems can also experience this code because accessory functions are often electronically controlled through the BCM.

How Is P2537 Diagnosed?

Proper diagnosis requires testing the ACC circuit, ignition switch, battery supply, and related modules.

Check for additional diagnostic trouble codes

Other BCM, battery, communication, or ignition-related codes can help identify the source of the problem.

Inspect the ignition switch

Technicians verify that the ACC position produces the correct voltage output.

Inspect wiring and connectors

The ACC circuit should be checked for:

Broken wires
Loose terminals
Corrosion
Heat damage
Moisture intrusion

Measure circuit voltage

A digital multimeter is used to verify:

Battery voltage
ACC circuit voltage
Ground integrity
Voltage drop

Inspect battery terminals

Battery connections should be checked for corrosion and proper tightness.

Review live scan data

A professional scan tool allows technicians to monitor:

Ignition switch position
ACC status
BCM commands
Battery voltage
Module communication

Inspect fuses and relays

Accessory-related fuses and relays should be tested.

Test the charging system

The alternator should be checked to ensure proper electrical output.

How to Fix P2537

The correct repair depends on the underlying cause.

Common repairs include:

Replacing a faulty ignition switch
Repairing damaged ACC wiring
Replacing damaged wiring harness sections
Cleaning corroded electrical connectors
Repairing loose electrical terminals
Cleaning battery terminals
Replacing a weak battery
Replacing a faulty accessory relay
Replacing damaged fuses or fuse holders
Repairing poor ground connections
Repairing BCM-related faults
Repairing CAN bus communication problems
Removing incorrectly installed aftermarket electrical accessories
Updating BCM or ECM software if recommended
Replacing the ECM if internal failure is confirmed

After repairs are completed, technicians should clear the diagnostic code and verify proper accessory operation in all ignition switch positions.

Can You Drive With P2537?

Yes, in most cases, the vehicle can still be driven.

Because the ACC circuit mainly controls accessory systems, engine operation may not be immediately affected.

However, ignoring the problem may result in:

Loss of electrical accessories
Battery discharge problems
Module communication issues
Future ignition switch failures
Intermittent electrical problems

The vehicle should still be inspected to prevent further electrical faults.

Is P2537 a Serious Code?

P2537 is generally considered a moderate severity diagnostic trouble code.

It usually does not immediately prevent driving, but it indicates a problem in the vehicle's electrical power management system.

Ignoring the code may lead to:

Accessory system failures
Battery drain
Electronic module communication problems
Progressive ignition switch problems

Early diagnosis helps maintain reliable electrical operation.

How to Prevent P2537

Regular electrical system maintenance can help prevent ACC circuit problems.

Recommended preventive maintenance includes:

Inspect ignition switch operation regularly.
Keep battery terminals clean and secure.
Test battery condition periodically.
Inspect wiring harnesses for damage.
Protect connectors from moisture and corrosion.
Repair electrical faults promptly.
Avoid excessive electrical loads on accessory circuits.
Ensure aftermarket electronics are installed correctly.
Replace worn ignition switches before complete failure.

Proper maintenance helps ensure stable accessory power delivery and reliable communication between the ignition switch, BCM, and ECM.

Final Thoughts

P2537 Ignition Switch Accessory Position Circuit Low indicates that the ECM or another control module has detected insufficient voltage in the ignition switch ACC circuit. The most common causes include a worn ignition switch, weak battery, poor battery connections, damaged wiring, loose or corroded connectors, faulty accessory relays, blown fuses, poor grounds, BCM problems, communication faults, or incorrectly installed aftermarket electrical accessories.

Although this code usually does not immediately affect engine operation, it can cause unreliable accessory operation, battery drain problems, and future electrical failures. Prompt diagnosis and repair restore proper accessory power control and ensure reliable operation of the vehicle's electrical systems.