P2ADD code meaning
Reductant Tank Temperature Sensor B Circuit Intermittent/Erratic
Powertrain system Generic code P2Axx codes Check engine light
What P2ADD means
P2ADD judges how the sensor B signal moves over time instead of how high it is. Fluid in a tank warms and cools slowly, so sudden jumps suggest a loose contact or a failing element. GM's 2017 and 2018 diesel tables compare every raw thermistor sample with an envelope that starts at the last good value and widens toward the −55 °C and 155 °C limits as bad samples pile up; 40 failures in 50 samples give a Type A code. In the 2025 DEF controller the tank unit adds up the absolute temperature changes across a window of 14 samples taken every 1.3 s and fails above 6 °C, one fail in three windows being enough; while P2ADB or P2ADC is present this test is suspended. GM also lists P2ADD in bulletin 21-NA-149 on harness chafing with the 3.0 L LM2 diesel.
P2ADD at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2ADD
- Check engine light that may return after clearing
- Jumping DEF temperature in live data
- DEF or SCR warning message
Common causes of P2ADD
- Most likelyLoose or corroded contact at the tank sensor connector
- PossibleChafed harness with intermittent contact
- PossibleDegrading thermistor in the quality or tank sensor unit
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant tank temperature sensor bWiring harnessSCR module
What each part of P2ADD means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| A | Area: hybrid propulsion. |
| DD | The exact fault in that area. |
What to do next
- Note P2ADD 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 P2ADD
What does P2ADD mean?
P2ADD means "Reductant Tank Temperature Sensor B Circuit Intermittent/Erratic". P2ADD judges how the sensor B signal moves over time instead of how high it is. It is a generic code, so it means the same on every make.
Is it safe to drive with P2ADD?
Drive gently and only to a workshop. With P2ADD the car can go into limp mode (reduced power) to protect itself.
Will P2ADD fail an emissions test?
Yes, it can. P2ADD 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 P2ADD to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P2ADD clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.