14-05-2025
5 min.
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P2535 Ignition Switch Run/Start Position Circuit High

P2535 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 Run/Start Position Circuit is operating with a voltage higher than the manufacturer-specified range.

In simple terms, the ECM is receiving an unexpectedly high electrical signal from the ignition switch when it should be receiving a normal RUN or START position signal. This may be caused by a wiring short, ignition switch failure, charging system overvoltage, or a problem with another control module involved in ignition management.

The ignition switch controls two critical states:

RUN position: Supplies continuous electrical power to the ECM, fuel injection system, ignition system, transmission control module, emissions systems, and other vehicle electronics.
START position: Sends the engine start request signal and allows the starter system to engage.

When the ECM detects excessive voltage in this circuit, it stores diagnostic code P2535 and usually activates the Check Engine Light.

What Does P2535 Mean?

The ignition switch communicates the driver's request through electrical signals.

During normal operation:

The ignition switch sends a stable voltage signal when turned to RUN.
The ignition switch sends a start request signal when turned to START.
The ECM verifies that the voltage level matches expected values.

If the voltage is higher than the programmed limit, the ECM identifies the circuit as having a high voltage condition and stores P2535.

Possible reasons include:

The signal wire receiving battery voltage directly.
A failed ignition switch internally connecting circuits incorrectly.
A damaged relay supplying excessive voltage.
Charging system voltage exceeding normal limits.
A control module sending incorrect ignition status information.

Unlike P2533, which indicates a general Run/Start circuit malfunction, and P2534, which indicates low voltage, P2535 specifically identifies a high-voltage condition.

Common Symptoms of P2535

The symptoms may vary depending on how the ignition circuit is affected.

Common symptoms include:

Check Engine Light illuminated
Intermittent starting problems
Engine may not start
Engine stalls unexpectedly
Electrical accessories operate incorrectly
Dashboard warning lights remain illuminated
Instrument cluster resets
Radio or infotainment system restarts
Transmission may enter fail-safe mode
Multiple electrical warning lights appear
Additional ignition or communication fault codes

Some vehicles may continue running normally but develop sudden electrical problems.

Common Causes of P2535

Several electrical problems can cause excessive voltage in the ignition Run/Start circuit.

Short to battery voltage

The ignition signal wire may contact a constant battery power source, causing a higher-than-normal reading.

Faulty ignition switch

Internal contacts may fail and incorrectly connect power circuits together.

Damaged wiring

The ignition wiring harness may develop:

Melted insulation
Pinched wires
Chafed wiring
Incorrect previous repairs
Heat damage

Faulty ignition relay

A sticking relay may supply power continuously or incorrectly.

Charging system overvoltage

A faulty alternator or voltage regulator may increase system voltage beyond normal levels.

Loose or corroded connectors

Poor connections can create abnormal electrical readings.

Faulty Body Control Module (BCM)

The BCM may incorrectly process or transmit ignition status signals.

CAN bus communication problems

Communication errors between control modules may cause incorrect ignition information.

Improper aftermarket electrical installation

Remote starters, alarms, immobilizers, or other accessories may interfere with ignition circuits.

ECM malfunction

Although rare, the ECM itself may incorrectly interpret ignition circuit voltage.

Vehicles Commonly Affected by P2535

P2535 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 equipped with push-button start systems may also experience this code if the electronic ignition authorization system detects abnormal voltage.

How Is P2535 Diagnosed?

Proper diagnosis requires checking the ignition circuit, power supply system, and related modules.

Check for additional diagnostic trouble codes

Other BCM, starter, immobilizer, communication, or charging system codes may provide useful information.

Inspect the ignition switch

Technicians verify that the ignition switch produces the correct RUN and START signals.

Inspect wiring and connectors

The ignition circuit is checked for:

Short circuits
Damaged insulation
Loose terminals
Corrosion
Heat damage
Moisture intrusion

Measure circuit voltage

A digital multimeter is used to check:

Battery voltage
RUN signal voltage
START signal voltage
Voltage drop
Ground integrity

Review live scan data

A professional scan tool allows technicians to monitor:

Ignition switch position
RUN status
START request
ECM input voltage
BCM communication
Battery and charging voltage

Inspect ignition relays and fuses

Faulty relays or poor fuse connections can create high-voltage conditions.

Test the charging system

The alternator and voltage regulator should be tested to confirm proper system voltage.

How to Fix P2535

The correct repair depends on the actual cause of the fault.

Common repairs include:

Replacing a faulty ignition switch
Repairing wiring shorted to battery voltage
Replacing damaged wiring harnesses
Cleaning corroded connectors
Repairing loose electrical terminals
Replacing faulty ignition relays
Repairing charging system overvoltage problems
Replacing a faulty alternator or voltage regulator
Repairing BCM-related faults
Correcting CAN bus communication problems
Removing improperly installed aftermarket electrical accessories
Updating ECM or BCM software when applicable
Replacing the ECM if internal failure is confirmed

After repairs are completed, the diagnostic code should be cleared and the ignition system should be tested through multiple start cycles.

Can You Drive With P2535?

Driving with P2535 is not recommended.

Although some vehicles may continue operating, excessive ignition circuit voltage can cause:

Unexpected engine shutdown
Starting failures
Electrical system instability
Damage to sensitive electronic components

If the vehicle experiences stalling or electrical problems, it should be inspected immediately.

Is P2535 a Serious Code?

P2535 is generally considered a high severity diagnostic trouble code because it affects the ignition power supply and starting system.

Ignoring the fault may lead to:

Complete no-start condition
Engine stalling while driving
Damage to electronic control modules
Communication problems between vehicle systems
Unpredictable electrical behavior

Early diagnosis helps prevent further electrical system problems.

How to Prevent P2535

Regular maintenance of the ignition and electrical systems can help prevent this code.

Recommended preventive maintenance includes:

Inspect ignition wiring regularly.
Keep electrical connectors clean and protected.
Repair damaged wiring immediately.
Test battery and alternator operation periodically.
Replace failing voltage regulators before overvoltage occurs.
Replace worn ignition switches when necessary.
Avoid incorrect aftermarket electrical modifications.
Check ignition relays during electrical system inspections.

Proper electrical system maintenance helps ensure stable ignition signals and reliable communication between the ignition switch, BCM, and ECM.

Final Thoughts

P2535 Ignition Switch Run/Start Position Circuit High indicates that the ECM has detected excessive voltage in the ignition switch Run/Start Position Circuit. The most common causes include a short to battery voltage, faulty ignition switch, damaged wiring, defective ignition relay, charging system overvoltage, BCM faults, CAN bus communication problems, or improperly installed aftermarket electrical equipment.

Although an ECM failure is possible, ignition circuit wiring problems and electrical supply faults are much more common. Because this circuit controls both engine starting and normal vehicle operation, the problem should be diagnosed promptly to prevent unexpected stalling, no-start conditions, and potential damage to vehicle electronics.