AutoCodes – Dodge – U12A4 Dodge

U12A4 Dodge Code - Lost Communication With Ammonia Sensor

Quick Answer

The Ammonia (NH3) Sensor is located in the middle of the aftertreatment SCR Catalyst and is used to measure the ammonia concentration in the aftertreatment system. Common causes include Faulty Ammonia Sensor Module, Ammonia Sensor Module harness is open or shorted, Ammonia Sensor Module 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: U12A4 Dodge indicates Lost Communication With Ammonia Sensor.
Common causes: Common causes include Faulty Ammonia Sensor Module, Ammonia Sensor Module harness is open or shorted, Ammonia Sensor Module 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 1,426

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 May 12, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U12A4 Dodge Description

The Ammonia (NH3) Sensor is located in the middle of the aftertreatment SCR Catalyst and is used to measure the ammonia concentration in the aftertreatment system. The Ammonia Sensor Module is a smart device that performs its own internal diagnostics, as well as diagnostics on the sensor and reports malfunctions back to the Powertrain Control Module (PCM) via the J1939 data link. The PCM will illuminate the Malfunction Indicator Lamp (MIL) after the diagnostic runs and fails in one drive cycle.

OBDII Code U12A4 Dodge - Lost Communication With Ammonia Sensor - AutoCodes.com — U12A4 Dodge Code - Lost Communication With Ammonia Sensor

What does this mean?

What are the Possible Causes of the DTC U12A4 Dodge?

Faulty Ammonia Sensor Module
Ammonia Sensor Module harness is open or shorted
Ammonia Sensor Module circuit poor electrical connection
Faulty Powertrain Control Module (PCM)

How to Fix the DTC U12A4 Dodge?

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 U12A4 Dodge 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 U12A4 Dodge Code

1. What does the OBDII code U12A4 for Dodge, "Lost Communication With Ammonia Sensor," indicate?

This code indicates that the vehicle's onboard diagnostic system has lost communication with the ammonia sensor.

2. What are common symptoms of the U12A4 code?

Common symptoms include the check engine light illuminating on the dashboard and potential issues with the vehicle's emissions system.

3. What are possible causes of the U12A4 code being triggered?

Possible causes include a faulty ammonia sensor, damaged wiring or connectors related to the sensor, or issues with the vehicle's electronic control module.

4. How can I diagnose the U12A4 code?

Diagnosing the U12A4 code typically involves using a diagnostic scanner to retrieve the specific fault code, inspecting the ammonia sensor and related components for damage, and testing the sensor's functionality.

5. Can I still drive my vehicle with the U12A4 code present?

It is generally not recommended to drive the vehicle with the U12A4 code present, as it can indicate potential issues with the emissions system that may affect the vehicle's performance and emissions output.

6. How can I repair the U12A4 code?

Repairing the U12A4 code may involve replacing the faulty ammonia sensor, repairing or replacing damaged wiring or connectors, or addressing any underlying issues with the electronic control module.

7. Are there any DIY tips for fixing the U12A4 code?

DIY tips for fixing the U12A4 code include checking the sensor's wiring and connectors for any visible damage, ensuring proper connections, and consulting the vehicle's service manual for specific repair instructions.

8. Can resetting the fault codes clear the U12A4 code?

Resetting the fault codes may temporarily clear the U12A4 code, but if the underlying issue is not addressed, the code is likely to reappear once the diagnostic system detects the communication loss again.

9. Is it necessary to visit a mechanic for the U12A4 code?

Due to the technical nature of diagnosing and repairing issues related to the ammonia sensor and emissions system, it is recommended to visit a qualified mechanic or dealership for proper diagnosis and repair of the U12A4 code.

10. How much does it cost to fix the U12A4 code?

The cost of fixing the U12A4 code can vary depending on the specific cause of the issue, the required repairs or replacements, and labor costs. It is advisable to obtain a professional diagnosis to get an accurate estimate of the repair costs.