Reductant Injection Air Pressure Sensor "A" Circuit High
The reductant injection air pressure sensor A circuit is reading abnormally high, preventing the SCR (Selective Catalytic Reduction) system from properly injecting diesel exhaust fluid. This can damage the catalytic converter and reduce engine efficiency if not addressed promptly.
What You Might Notice
- Reduced fuel efficiency
- Excessive black smoke from exhaust
- Diminished engine performance
- Check engine light illumination
- Other SCR-related fault codes present
Most Common Causes
- 1
Defective reductant air pressure sensor
The injection air pressure sensor is malfunctioning or failing, causing it to send abnormally high voltage signals to the engine control module.
- 2
Wiring or connector issues
Corroded, damaged, or loose connections in the sensor circuit can cause erratic high readings and poor signal transmission.
- 3
Reductant system blockage
Clogged injectors or supply lines in the SCR reductant system can cause back pressure that triggers the sensor's high reading response.
- 4
Engine control module malfunction
A faulty PCM/ECM may misinterpret normal sensor signals as high pressure, though this is less common than sensor failure.
How to Diagnose It
- 1
Check Defective reductant air pressure sensor — The injection air pressure sensor is malfunctioning or failing, causing it to send abnormally high voltage signals to the engine control module.
- 2
Check Wiring or connector issues — Corroded, damaged, or loose connections in the sensor circuit can cause erratic high readings and poor signal transmission.
- 3
Check Reductant system blockage — Clogged injectors or supply lines in the SCR reductant system can cause back pressure that triggers the sensor's high reading response.
- 4
Check Engine control module malfunction — A faulty PCM/ECM may misinterpret normal sensor signals as high pressure, though this is less common than sensor failure.
How to Fix It
- 1
Replace reductant air pressure sensor
Remove the defective sensor from the reductant injection system and install a new OEM or quality aftermarket sensor calibrated for your vehicle.
- 2
Inspect and repair wiring/connectors
Check the sensor circuit wiring for corrosion, breaks, or bent pins. Clean connector contacts with dielectric grease or replace corroded connectors.
- 3
Flush and clear reductant system
Perform a complete reductant system flush to remove blockages in supply lines and injectors that may be causing excessive back pressure.
- 4
Reprogram or replace PCM/ECM
Update engine control module software to latest calibration, or replace the module if it continues to misinterpret sensor signals after other repairs.
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