AutoCodes – Generic – P21B0

P21B0 Code - Reductant Level Sensor 3 Circuit High Voltage

Quick Answer

The reductant level/temperature sensor is a solid-state device that provides the Engine Control Module (ECM) with information on reductant level and temperature. Common causes include Faulty Reductant Level Sensor 3, Reductant Level Sensor 3 harness is open or shorted, Reductant Level Sensor 3 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P21B0 indicates Reductant Level Sensor 3 Circuit High Voltage.
Common causes: Common causes include Faulty Reductant Level Sensor 3, Reductant Level Sensor 3 harness is open or shorted, Reductant Level Sensor 3 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 3,778

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 10, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P21B0 Description

The reductant level/temperature sensor is a solid-state device that provides the Engine Control Module (ECM) with information on reductant level and temperature. The level/temperature sensor receives system voltage directly from the underhood electrical center and ground through a chassis ground circuit. The level sensor consists of three sensing elements. Reductant level sensor 3 is highest, reductant level sensor 2 is located between sensors 1 and 3. Reductant level sensor 1 is located at a low reductant level. Reductant level sensor 3 is located at less than half the range of the DEF tank level. The scan tool will display Active when the level sensors are in contact with the reductant and Inactive when not in contact with the reductant. An integrated temperature sensor monitors reductant temperature. Reductant level and temperature signals are processed within the sensor and supplied to the ECM as serial data messages. The ECM will set a DTC when it detects an invalid level or temperature serial data message from the sensor. The Diagnostic Trouble Code (DTC) will be set when the ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is between 3.56-4.74 V for greater than 3 s. A voltage within this range indicates an open circuit.

OBDII Code P21B0 - Reductant Level Sensor 3 Circuit High Voltage - AutoCodes.com — P21B0 Code - Reductant Level Sensor 3 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P21B0?

Faulty Reductant Level Sensor 3
Reductant Level Sensor 3 harness is open or shorted
Reductant Level Sensor 3 circuit poor electrical connection

How to Fix the DTC P21B0?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P21B0 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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Information for Specific Makes

P21B0 Chevrolet — Reductant Level Sensor 3 Circuit High Voltage
P21B0 Ford — Reductant Level Sensor 'C' Circuit High
P21B0 GMC — Reductant Level Sensor 3 Circuit High Voltage

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.