P2039 code meaning
Reductant Injection Air Pressure Sensor A Circuit Low
Powertrain system Generic code P20xx codes Check engine light
What P2039 means
P2039 is stored when the signal of injection air pressure sensor A sits below the lowest voltage a working sensor can deliver. Deutz documents it on its EMR L1 controller as P2039-00 under SPN 4335 and lumps two causes together: a grounded signal and an open circuit, since the input is pulled low when the signal wire is interrupted. A loss of the 5 V reference is another common reason for a reading near zero. Because the controller can no longer confirm that atomizing air is present, it stops DEF injection; Deutz engines then run without NOx reduction until the inducement logic of the machine steps in. The opposite fault is P2040, and electrical faults of the sensor supply fall under P2037.
P2039 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2039
- Emission warning lamp on
- DEF injection stopped
- Power derate after a while on machines with inducement
Common causes of P2039
- Most likelySignal wire open or shorted to ground
- Possible5 V reference to the sensor lost
- PossibleSensor output stuck low
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant air pressure sensor
What each part of P2039 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 39 | The exact fault in that area. |
What to do next
- Note P2039 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2039
What does P2039 mean?
P2039 means "Reductant Injection Air Pressure Sensor A Circuit Low". P2039 is stored when the signal of injection air pressure sensor A sits below the lowest voltage a working sensor can deliver. It is a generic code, so it means the same on every make.
Is it safe to drive with P2039?
Drive gently and only to a workshop. With P2039 the car can go into limp mode (reduced power) to protect itself.
Will P2039 fail an emissions test?
Yes, it can. P2039 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2039 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P2039 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.