P2ADC code meaning
Reductant Tank Temperature Sensor B Circuit High
Powertrain system Generic code P2Axx codes Check engine light
What P2ADC means
P2ADC is the upper limit check on the same sensor B: the reported DEF temperature is higher than the fluid in the tank could ever get. In GM's 2017 and 2018 diesel calibrations the quality sensor thermistor has to exceed 155 °C in 40 of 50 samples, with cranking finished and more than 11 V at the powertrain relay; the outcome is a Type A code. GM's 2025 DEF controller draws the line much lower at 90 °C, held for 2 s and again computed inside the smart tank unit. GM bulletin 21-NA-149 names P2ADC among the codes that a chafed engine harness produced on 2021 trucks and SUVs with the 3.0 L LM2 diesel. Such a high value usually means trouble in the sensor electronics or its wiring rather than real heat. Too low and unsteady signals are handled by P2ADB and P2ADD.
P2ADC 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 P2ADC
- Check engine light on
- DEF system message, often together with other harness-related codes
- Possible inducement countdown toward reduced power
Common causes of P2ADC
- Most likelyInternal fault in the quality sensor or smart tank sensor unit
- PossibleChafed engine harness disturbing the sensor circuit
- Less likelyCorroded or loose pins at the tank sensor connector
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 P2ADC 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. |
| DC | The exact fault in that area. |
What to do next
- Note P2ADC 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 P2ADC
What does P2ADC mean?
P2ADC means "Reductant Tank Temperature Sensor B Circuit High". P2ADC is the upper limit check on the same sensor B: the reported DEF temperature is higher than the fluid in the tank could ever get. It is a generic code, so it means the same on every make.
Is it safe to drive with P2ADC?
Drive gently and only to a workshop. With P2ADC the car can go into limp mode (reduced power) to protect itself.
Will P2ADC fail an emissions test?
Yes, it can. P2ADC 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 P2ADC to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P2ADC clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.