Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is getting a signal that's too high from the part that controls alternative fuel. Imagine if you were trying to listen to music but the volume was way too high and you couldn't turn it down.
The signal from the alternative fuel disable circuit is higher than the expected range, indicating a potential issue with the circuit or related components.
The P25C2 code is triggered when the Powertrain Control Module (PCM) detects a high voltage condition in the alternative fuel disable signal circuit. This could be due to a short to voltage, an open circuit, or a faulty component within the circuit.
• Check Engine Light is on
• Alternative fuel system not operating
• Possible reduced engine performance
• Fuel efficiency issues
• Faulty alternative fuel disable switch
• Short to voltage in the circuit
• Open circuit condition
• Faulty PCM
• Wiring issues
PCM: Powertrain Control Module
OBD-II: On-Board Diagnostics II
• Scan the vehicle for additional codes.
• Inspect the wiring and connectors for damage or corrosion.
• Test the alternative fuel disable switch for proper operation.
• Check for shorts or opens in the circuit.
• Test the PCM for faults.
• Repair or replace damaged wiring or connectors.
• Replace the alternative fuel disable switch if faulty.
• Repair any shorts or open circuits.
• Replace the PCM if it is determined to be faulty.
• OBD-II scanner
• Multimeter
• Wiring diagram
• Basic hand tools
$100 - $500
Moderate
• Chevrolet Volt
• Toyota Prius
• Nissan Leaf
• Regularly inspect and maintain wiring and connectors.
• Ensure proper operation of alternative fuel systems.
• Schedule regular vehicle maintenance.
Sensor Issue
• Do not ignore the Check Engine Light.
• Consult a professional mechanic if unsure.
• Regularly check vehicle systems for proper operation.
Check with your vehicle manufacturer as this may be covered under emissions warranty.
This code is relatively uncommon and is typically associated with vehicles equipped with alternative fuel systems.
Moderate – It is recommended to address this issue to ensure proper operation of the alternative fuel system.
Operating a vehicle with a malfunctioning alternative fuel system may not comply with emissions regulations.
• Vehicle must be running.
• Alternative fuel system must be engaged.
The alternative fuel disable switch is typically located near the fuel system components or integrated into the vehicle's PCM.
Q: Can I drive my car with this code?
A: It is possible to drive, but it's recommended to fix the issue to ensure the alternative fuel system works properly.
Q: Will this affect my car's performance?
A: Yes, it might reduce performance or fuel efficiency if the alternative fuel system is not functioning properly.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.