The P20A8: Reductant Injection Air Pressure Control Valve Circuit Low fault code refers to a situation where the circuit controlling the reductant injection air pressure control valve is receiving lower voltage than expected. This valve regulates air pressure for the proper injection of diesel exhaust fluid (DEF) into the exhaust system. Low voltage in this circuit may cause the valve to malfunction, resulting in ineffective DEF dosing and poor emissions control. The problem may stem from a wiring issue, a faulty valve, or a malfunctioning control module.
P20A8 – Quick Overview
Code | Information |
---|---|
Meaning | P20A8: Reductant Injection Air Pressure Control Valve Circuit Low |
Is it serious? | Yes, it can lead to improper DEF dosing, affecting emissions control and potentially triggering warning lights. |
Possible causes | – Low voltage in the reductant injection air pressure control valve circuit – Faulty control valve – Faulty control module |
How to diagnose? | – Measure voltage in the control valve circuit – Test the reductant injection air pressure control valve – Check the control module functionality |
P20A8 Meaning
The P20A8 code indicates that the reductant injection air pressure control valve circuit is experiencing low voltage, which can lead to improper operation of the valve. This valve controls the air pressure necessary to inject DEF into the exhaust system, and low voltage can disrupt the flow of DEF, leading to higher emissions and poor system performance. The issue may be caused by faulty wiring, a malfunctioning valve, or a faulty control module.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional related fault codes that might provide further details about the reductant system issue. | OBD-II Scanner |
Measure Voltage in the Circuit | Use a multimeter to measure the voltage in the reductant injection air pressure control valve circuit and compare it to the manufacturer’s specifications to confirm low voltage. | Multimeter |
Test the Reductant Injection Air Pressure Control Valve | Use a diagnostic tool to test the valve and ensure it is functioning within the required voltage range. Replace the valve if necessary. | Multimeter, Diagnostic Tool |
Check the Control Module Functionality | Inspect the control module responsible for managing the valve to ensure it is sending the correct signals and not causing the low voltage issue. | Diagnostic Tool |
Clear the Code and Test Drive | After completing repairs, clear the fault code using an OBD-II scanner and take the vehicle for a test drive to verify that the issue has been resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | Re-scan the system after the test drive to ensure the P20A8 code does not return. If the code reappears, further diagnostics may be needed. | OBD-II Scanner |

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