P2ADA: Reductant Tank Temperature Sensor B Circuit Range/Performance

P2ADA checks whether the second DEF tank temperature reading is plausible. GM documents it twice. In its 2017–2018 diesel tables (and again in 25OBDG06C) it is the DEF quality sensor temperature offset: after more than 28,800 s off, the quality sensor's thermistor may differ from the average of the exhaust temperature sensors by no more than 35 °C; 40 of 50 samples failing set a Type A code. The 2025 DEF controller compares, at key on after a soak of over 8 h, the tank sensor B value with the secondary device temperature and fails beyond 21 °C (3 s out of 6, Type A). GM bulletin 21-NA-149 lists P2ADA among the codes from engine harness chafing on 2021 3.0L LM2 trucks. Circuit faults are P2ADB to P2ADE.

Symptoms

• Check engine light after a cold start
• DEF or SCR warning message

Most likely causes

• DEF quality sensor with drifting temperature element
• Reference temperature sensors reading wrong
• Chafed engine harness disturbing the signals
• Controller software needing an update

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Compare the reading with other engine data while varying the engine speed.
3. Look for white crystals around the injector and the tank
4. Check connectors and heaters with the scanner
5. Run the dosing test available on your diagnostic tool
6. Replace parts only when the test points to that component

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2ADA means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• A: Hybrid or air and fuel
• DA: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2ADA?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P2ADA?

The most common causes are: dEF quality sensor with drifting temperature element; reference temperature sensors reading wrong; chafed engine harness disturbing the signals.

Related codes

• P2ADBReductant Tank Temperature Sensor B Circuit Low
• P2ADCReductant Tank Temperature Sensor B Circuit High
• P2ADDReductant Tank Temperature Sensor B Circuit Intermittent/Erratic
• P2ADEReductant Tank Temperature Sensor B Circuit
• P205BReductant Tank Temperature Sensor A Circuit Range/Performance

Sources

• gsi.ext.gm.com: 25OBDG04A
• gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
• gsi.ext.gm.com: 17OBDG04 Engine Diagnostics
• gsi.ext.gm.com: 25OBDG06C

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.