AutoCodes – GMC – P203B GMC

P203B GMC Code - Reductant Level Sensor Performance

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, Reductant Level Sensor harness is open or shorted, Reductant Level Sensor 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: P203B GMC indicates Reductant Level Sensor Performance.
Common causes: Common causes include Faulty Reductant Level Sensor, Reductant Level Sensor harness is open or shorted, Reductant Level Sensor 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 801

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 P203B 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 sensor 1 and 3. Reductant level sensor 1 is located at low reductant level. Reductant level sensor 3 is located at less than half 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 reductant level sensor indications are not plausible.

OBDII Code P203B GMC - Reductant Level Sensor Performance - AutoCodes.com — P203B GMC Code - Reductant Level Sensor Performance

What does this mean?

What are the Possible Causes of the DTC P203B GMC?

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

How to Fix the DTC P203B 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 P203B 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 P203B GMC Code

What does the OBDII code P203B mean for my GMC vehicle?

The P203B code indicates a problem with the reductant level sensor performance, which measures the amount of diesel exhaust fluid (DEF) in the tank.

What symptoms might I notice if my vehicle has a P203B code?

Common symptoms include warning lights on the dashboard, reduced engine performance, and possibly the vehicle entering limp mode until the issue is resolved.

What are some common causes of the P203B code?

Common causes include a faulty reductant level sensor, wiring issues (such as shorts or corrosion), or low levels of diesel exhaust fluid in the tank.

Can I drive my vehicle if the P203B code is present?

While you can technically drive the vehicle, it may enter limp mode to protect the engine, leading to reduced power and efficiency. It's advisable to address the code as soon as possible.

How can I diagnose the P203B code accurately?

To diagnose the P203B code, use an OBD-II scanner to confirm the code and check for any related codes, inspect the wiring and connectors of the reductant level sensor, and verify the DEF level.

What should I do if the reductant level is low but I still get a P203B code?

If the DEF level is adequate, inspect the reductant level sensor for any faults or wiring issues that may be causing incorrect readings.

Is it necessary to replace the reductant level sensor if I get a P203B code?

Not necessarily. While a faulty sensor is a common cause, it's important to perform a thorough diagnosis to rule out wiring issues or other related problems before replacing the sensor.

How can I prevent the P203B code from returning after repairs?

To prevent the P203B code from reappearing, ensure that the DEF tank is regularly filled, keep the sensor and wiring in good condition, and follow the manufacturer's maintenance recommendations.

Could a software update help with the P203B code?

In some cases, a software update for the vehicle's engine control module (ECM) can resolve issues related to the P203B code. Check with your dealer for any available updates.