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 part in your car that helps clean the exhaust is stuck and can't open. It's like a door that should open to let air in, but it's jammed shut.
The P20AB code indicates that the reductant injection air pressure control valve is not opening as it should, preventing proper air flow needed for the exhaust system's cleaning process.
The reductant injection air pressure control valve is responsible for regulating the air pressure used in the selective catalytic reduction (SCR) system. When this valve is stuck closed, it disrupts the proper functioning of the SCR system, which is crucial for reducing emissions by injecting a urea-based reductant into the exhaust stream.
• Check Engine Light is on
• Increased emissions
• Possible reduction in engine performance
• Faulty reductant injection air pressure control valve
• Electrical issues such as a short or open circuit
• Mechanical blockage or debris in the valve
Reductant: A substance used to reduce emissions in the exhaust system, often a urea-based solution.
SCR: Selective Catalytic Reduction, a system used to reduce nitrogen oxide emissions in diesel engines.
• Use an OBD-II scanner to confirm the P20AB code
• Inspect the wiring and connectors for damage
• Check the valve for mechanical blockages
• Replace the reductant injection air pressure control valve
• Repair or replace damaged wiring and connectors
• Clean any debris or blockages from the valve
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $400
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Ram 2500
• Regularly inspect and maintain the SCR system
• Use high-quality fuel and reductant
• Perform periodic emissions system checks
Emission Control System Issue
• Address this issue promptly to avoid increased emissions
• Consult a professional mechanic if unsure about repairs
Check vehicle warranty for coverage on emissions-related components
This code has become more common with the increased use of SCR systems in diesel engines to meet stricter emissions standards.
Moderate – While the vehicle may still be drivable, it is important to address this issue to ensure emissions compliance and avoid potential fines.
Driving with this issue may result in failing emissions tests and could lead to fines in areas with strict emissions regulations.
• Engine at operating temperature
• Vehicle in motion
The reductant injection air pressure control valve is typically located near the exhaust system, often close to the SCR catalyst.
Q: Can I drive my car with a P20AB code?
A: While the car may still operate, it's best to fix the issue soon to avoid emissions problems.
Q: What happens if I ignore the P20AB code?
A: Ignoring it can lead to increased emissions and potential fines if your vehicle fails an emissions test.
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A wired color-screen reader with readiness hotkeys, live data, code definitions, and data logging.
Good for emissions-related codes because it exposes readiness monitors and live powertrain data.
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Specialty · Smoke machine
Helpful for finding EVAP and vacuum leaks that are hard to see with visual inspection alone.
Helpful for tracking down EVAP and vacuum leaks that can trigger emissions faults.
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Specialty · O2 sensor socket
Helpful when the code points toward exhaust or oxygen-sensor work and space is tight.
Useful when the diagnosis points toward oxygen-sensor removal or replacement.
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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.
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Fitment Required · Vehicle-fitment part
Relevant for airflow, fuel-trim, and intake-metering faults after confirming the sensor is actually at fault.
Airflow and fuel-trim codes can involve the mass air flow sensor after proper diagnosis.
Verify the sensor design and fitment for your exact vehicle.
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.