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 taking too long to start a special process that helps reduce pollution from the exhaust.
The vehicle's engine control module (ECM) is not entering closed-loop control for the reductant injection system within the expected time frame.
The P249C code indicates that the ECM has detected an excessive amount of time taken to enter closed-loop control for the reductant injection system. This system is responsible for injecting a urea-based solution (Diesel Exhaust Fluid) into the exhaust stream to reduce nitrogen oxide emissions in diesel engines. If the system does not reach closed-loop control quickly, it may not effectively reduce emissions.
• Check Engine Light is on
• Increased emissions
• Poor fuel economy
• Faulty reductant injector
• Defective NOx sensor
• Issues with the reductant heater
Reductant: A substance used to reduce emissions, often Diesel Exhaust Fluid (DEF) in diesel engines.
Closed-loop control: A system that uses feedback to regulate its operation, ensuring optimal performance.
• Check for any other related diagnostic trouble codes.
• Inspect the reductant injector for clogs or damage.
• Test the NOx sensor for proper operation.
• Replace the reductant injector if faulty.
• Repair or replace the NOx sensor if defective.
• Check and fix any wiring issues related to the system.
• OBD-II scanner
• Multimeter
• NOx sensor tester
$200 - $600
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly check and refill Diesel Exhaust Fluid (DEF).
• Perform routine maintenance on the exhaust system.
• Use high-quality DEF to prevent injector clogging.
Emission Control Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional promptly.
• Keep up with regular maintenance to avoid future issues.
Emission-related components may be covered under the vehicle's emissions warranty. Check with your dealer.
This code has become more common with the increased use of DEF systems in diesel engines to meet stricter emission standards.
Moderate – Addressing this issue is important to maintain emissions compliance and vehicle performance.
Ignoring emission-related codes can lead to increased pollution and potential legal issues in areas with strict emissions testing.
• Engine at operating temperature
• Vehicle driven under normal conditions
The reductant injector is usually located in the exhaust system, near the catalytic converter.
Q: Can I drive with a P249C code?
A: You can drive, but it's best to address the issue soon to prevent increased emissions and potential damage.
Q: Will a P249C code affect my vehicle's performance?
A: It may lead to increased emissions and slightly reduced fuel efficiency.
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Universal · Digital multimeter
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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.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.