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 a sensor in your car that helps control a special system to reduce pollution is not working right. It's like a part of your car's nose isn't smelling the air correctly.
The P2039 code is triggered when the Engine Control Module (ECM) detects a low voltage signal from the Reductant Injection Air Pressure Sensor A.
The Reductant Injection Air Pressure Sensor monitors the air pressure in the system that injects a fluid called reductant into the exhaust to reduce emissions. A 'circuit low' code indicates that the sensor is sending a signal that is below the expected range, which could be due to a fault in the sensor, wiring, or connections.
• Check Engine Light is on
• Possible reduction in engine performance
• Increased emissions
• Faulty Reductant Injection Air Pressure Sensor
• Damaged or corroded wiring or connectors
• Faulty ECM
Reductant: A fluid used in the exhaust system to reduce emissions.
ECM: Engine Control Module, the computer that controls engine functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the sensor with a multimeter to check for proper voltage and resistance.
• Replace the Reductant Injection Air Pressure Sensor if faulty.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Ford F-250
• Chevrolet Silverado
• Dodge Ram 2500
• Regularly inspect and maintain the exhaust system.
• Ensure proper connections and wiring integrity.
• Use high-quality reductant fluid.
Sensor Issue
• Do not ignore the Check Engine Light.
• Seek professional diagnosis if unsure.
• Regular maintenance can prevent such issues.
Check with your vehicle manufacturer for specific warranty coverage on emissions-related components.
This code has become more common as stricter emissions standards have been implemented, requiring more complex emission control systems.
Moderate – While the vehicle may still be drivable, emissions could be higher than normal, and performance may be affected.
Driving with a malfunctioning emissions system may violate local emissions laws and contribute to environmental pollution.
• Engine running
• Vehicle at operating temperature
The Reductant Injection Air Pressure Sensor is typically located near the reductant injection system, often in the exhaust area.
Q: Can I drive my car with a P2039 code?
A: It's possible to drive with this code, but it's not recommended due to potential increased emissions and possible performance issues.
Q: How can I prevent a P2039 code?
A: Regular maintenance and inspections of the exhaust and reductant systems can help prevent this code.
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.