AutoCodes – Generic – P21AF

P21AF Code - Reductant Level Sensor 3 Circuit Low 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: P21AF indicates Reductant Level Sensor 3 Circuit Low 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 948

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
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P21AF 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 less than 0.17 V for greater than 3 s. A voltage within this range indicates a short to ground.

OBDII Code P21AF - Reductant Level Sensor 3 Circuit Low Voltage - AutoCodes.com — P21AF Code - Reductant Level Sensor 3 Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P21AF?

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 P21AF?

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 P21AF 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.

Need more information about the P21AF code?

Need more information on how to fix the P21AF code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P21AF code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P21AF Chevrolet — Reductant Level Sensor 3 Circuit Low Voltage
P21AF GMC — Reductant Level Sensor 3 Circuit Low 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.

Frequently Asked Questions about P21AF Code

1. What are the common symptoms of OBDII code P21AF (Reductant Level Sensor 3 Circuit Low Voltage)?

The common symptoms of P21AF include the check engine light illuminating, reduced engine performance, and potential issues with the vehicle's emissions system.

2. What are the possible causes of OBDII code P21AF?

Possible causes of P21AF include a faulty reductant level sensor, wiring issues in the circuit, poor electrical connections, or a malfunctioning engine control module.

3. How serious is OBDII code P21AF (Reductant Level Sensor 3 Circuit Low Voltage)?

While the severity may vary, it is important to address P21AF promptly to prevent potential damage to the emissions system and ensure the vehicle meets environmental standards.

4. Can I continue driving with OBDII code P21AF active?

It is not recommended to drive with an active P21AF code, as it may lead to increased emissions, reduced fuel efficiency, and possible engine performance issues.

5. How can I diagnose OBDII code P21AF at home?

You can diagnose P21AF using an OBDII scanner to retrieve the code, inspecting the reductant level sensor and its wiring for any visible damage, and testing the sensor's voltage to determine if it falls within the specified range.

6. What are some repair tips for fixing OBDII code P21AF?

Repair tips for P21AF may include replacing the reductant level sensor, repairing any damaged wiring or connectors, ensuring proper sensor calibration, and clearing the code using an OBDII scanner.

7. How much does it typically cost to repair OBDII code P21AF?

The cost of repairing P21AF can vary depending on the extent of the issue, the parts needed, and whether you choose to do the repairs yourself or seek professional help. Costs may range from a few hundred to over a thousand dollars.

8. Can weather or environmental factors trigger OBDII code P21AF?

Extreme weather conditions or exposure to water and contaminants can potentially impact the reductant level sensor and trigger P21AF. It is essential to ensure the sensor is properly sealed and protected.

9. Will OBDII code P21AF cause my vehicle to fail an emissions test?

Yes, an active P21AF code can result in a failed emissions test due to issues with the reductant level sensor affecting the vehicle's emissions control system.

10. How can I prevent OBDII code P21AF from recurring in the future?

To prevent P21AF from recurring, it is essential to perform regular maintenance on the emissions system, keep the reductant level sensor and its components clean and free from damage, and address any related issues promptly.