Reductant Injection Air Pump Control Circuit/Open
P2059 indicates an open or faulty circuit in the reductant injection air pump control system, which is part of the selective catalytic reduction (SCR) aftertreatment system. This code means the engine control module cannot properly command or detect the air pump that pressurizes reductant (diesel exhaust fluid) for emission control.
What You Might Notice
- Reduced fuel efficiency
- Excessive black smoke from exhaust
- Diminished engine performance
- Check engine light illumination
- Potential limp mode activation
Most Common Causes
- 1
Defective Reductant Air Pressure Sensor
The sensor monitoring air pressure in the reductant system may be faulty, broken, or disconnected, preventing proper signal transmission to the engine control module.
- 2
Air Pump Control Circuit Wiring Issues
Corroded, loose, or damaged wiring and connectors in the air pump control circuit can cause an open circuit condition and loss of control signal.
- 3
Failed Reductant Air Pump
The air pump itself may have failed or become inoperative, resulting in no output or control feedback to the engine computer.
- 4
Engine Control Module Fault
A faulty engine control module or a programming issue may prevent proper communication with the air pump control circuit.
How to Diagnose It
- 1
Check Defective Reductant Air Pressure Sensor — The sensor monitoring air pressure in the reductant system may be faulty, broken, or disconnected, preventing proper signal transmission to the engine control module.
- 2
Check Air Pump Control Circuit Wiring Issues — Corroded, loose, or damaged wiring and connectors in the air pump control circuit can cause an open circuit condition and loss of control signal.
- 3
Check Failed Reductant Air Pump — The air pump itself may have failed or become inoperative, resulting in no output or control feedback to the engine computer.
- 4
Check Engine Control Module Fault — A faulty engine control module or a programming issue may prevent proper communication with the air pump control circuit.
How to Fix It
- 1
Inspect and Test Air Pressure Sensor
Locate the reductant air pressure sensor, inspect for damage and corrosion, test electrical continuity and output voltage, and replace if faulty.
- 2
Check Wiring and Connectors
Inspect the entire air pump control circuit wiring harness for breaks, corrosion, and loose connections. Repair or replace damaged wiring and reseat connectors.
- 3
Test and Replace Air Pump
Perform electrical and functional testing on the reductant air pump. If it fails to operate or respond to control signals, replace the pump assembly.
- 4
Clear Code and Road Test
After repairs, use a diagnostic scanner to clear the trouble code and perform a test drive to verify the air pump system operates correctly and the code does not return.
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