AutoCodes – GMC – P21B0 GMC

P21B0 GMC 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 High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P21B0 GMC 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: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 764

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 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
FAQs
Comments
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Code P21B0 GMC 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 GMC - Reductant Level Sensor 3 Circuit High Voltage - AutoCodes.com — P21B0 GMC Code - Reductant Level Sensor 3 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P21B0 GMC?

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 GMC?

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 GMC 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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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.

Frequently Asked Questions about P21B0 GMC Code

1. What are the common symptoms of OBDII code P21B0 (GMC) related to the Reductant Level Sensor 3 Circuit High Voltage?

The common symptoms include the check engine light being illuminated, reduced fuel efficiency, and potential issues with the vehicle's emissions system.

2. What causes OBDII code P21B0 (GMC) indicating Reductant Level Sensor 3 Circuit High Voltage?

The code P21B0 is typically caused by a malfunction in the Reductant Level Sensor 3 circuit, which can be due to wiring issues, sensor failure, or problems with the DEF (diesel exhaust fluid) system.

3. How can I diagnose the problem related to OBDII code P21B0 (GMC)?

Diagnosing the issue involves using an OBDII scanner to read the code and check the Reductant Level Sensor 3 circuit for any visible damage or corrosion. Additionally, testing the sensor's resistance and checking the DEF system components can help pinpoint the problem.

4. Can I continue driving with OBDII code P21B0 (GMC) present?

While driving with the code may be possible, it is not recommended as it can lead to reduced fuel efficiency and potential damage to the emissions system. It is advisable to address the issue promptly.

5. How can I repair OBDII code P21B0 (GMC) related to the Reductant Level Sensor 3 Circuit High Voltage?

Repairing the issue involves inspecting and repairing any damaged wiring, replacing the Reductant Level Sensor 3 if faulty, and ensuring proper functioning of the DEF system components. Clearing the code after repairs is also necessary.

6. Are there any DIY tips for fixing OBDII code P21B0 (GMC)?

While some basic troubleshooting like checking for loose connections or damaged wires can be done DIY, it is recommended to seek professional help for a comprehensive diagnosis and repair of the Reductant Level Sensor 3 Circuit High Voltage issue.

7. How much does it cost to repair OBDII code P21B0 (GMC) indicating Reductant Level Sensor 3 Circuit High Voltage?

The cost of repair can vary depending on the extent of the issue, the need for parts replacement, and labor charges. It is advisable to get a few quotes from reputable mechanics or service centers to compare prices.

8. Can a faulty Reductant Level Sensor 3 cause other problems in the vehicle?

Yes, a faulty Reductant Level Sensor 3 can lead to issues with the vehicle's emissions system, reduced fuel efficiency, and potentially trigger other related trouble codes if not addressed promptly.

9. How often does OBDII code P21B0 (GMC) occur in vehicles?

The occurrence of OBDII code P21B0 (GMC) related to the Reductant Level Sensor 3 Circuit High Voltage can vary depending on the vehicle's make, model, and usage. It is not one of the most common codes but can still occur in vehicles equipped with DEF systems.

10. Is it possible to prevent OBDII code P21B0 (GMC) from appearing in the future?

Regular maintenance of the vehicle's emissions system, including the Reductant Level Sensor 3 and DEF components, can help prevent issues that lead to the appearance of code P21B0. Following the manufacturer's recommended service schedule is key to avoiding such problems.