P2ADC: Reductant Tank Temperature Sensor B Circuit High

What it means

Voltage on the reductant tank B temperature sensor signal line is above the expected window. Wire shorted to B+ or sensor open.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The reductant tank B temperature sensor reports the DEF tank temperature to the emissions control module so it can manage reductant dosing and cold-weather operation. This code sets when the sensor signal is higher than the module's expected range, which can happen with a signal short to battery voltage, an open sensor, or a poor connector contact.

Common causes

Most likely first.

1. Signal wire shorted to B+
2. Open sensor
3. Connector pins corroded - high contact resistance

Symptoms

• Check engine light or NOx warning on
• AdBlue/DEF level or quality warning
• Possible no-start countdown after ignore period
• Failed emissions inspection (NOx)

How to diagnose it

1. Record freeze-frame data and check live data for reductant tank B temperature, noting whether the reading is implausibly high or fixed.
2. With the vehicle safely parked, inspect the tank B sensor connector and nearby harness for corrosion, loose pins, damage, or contact with a power source.
3. Check that the connector terminals grip correctly and that no pin is pushed back, then reconnect it securely.
4. Using the vehicle wiring diagram, check the sensor signal for a short to battery voltage and inspect the sensor circuit for an open.
5. Test the tank B temperature sensor and circuit against the manufacturer's specification, separating a failed sensor from a wiring or connector fault.

Common fixes

• Clean and securely reconnect corroded or loose tank B sensor terminals.
• Repair a damaged signal wire or wiring short to battery voltage.
• Replace the reductant tank B temperature sensor if it is open or fails testing.
• Clear the code and confirm the live temperature reading responds plausibly.

Can I keep driving?

The vehicle may remain driveable, but the DEF or NOx warning and a no-start countdown may follow if the emissions system cannot verify reductant conditions. Avoid ignoring the warning or making unnecessary trips; arrange diagnosis promptly, especially if a countdown is displayed.