AutoCodes – Chrysler – U12A4 Chrysler

U12A4 Chrysler 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 Chrysler 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 562

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

What does this mean?

What are the Possible Causes of the DTC U12A4 Chrysler?

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 Chrysler?

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 Chrysler 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 Chrysler Code

1. What are common symptoms of the OBDII code U12A4 Chrysler (Lost Communication With Ammonia Sensor)?

- Common symptoms include the check engine light coming on, poor engine performance, and potential issues with emissions.

2. What are possible causes of the U12A4 code in Chrysler vehicles?

- Possible causes include a faulty ammonia sensor, damaged wiring or connectors, software issues, or a malfunctioning control module.

3. How can I diagnose the U12A4 code in my Chrysler vehicle?

- Diagnosis typically involves using a scan tool to read the code, checking the wiring and connectors for damage, and testing the ammonia sensor's functionality.

4. Can I still drive my car with the U12A4 code present?

- It's generally not recommended to drive your car with this code active, as it may lead to poor performance or potential damage to the vehicle.

5. How can I repair the U12A4 code in my Chrysler vehicle?

- Repair options typically include replacing the faulty ammonia sensor, repairing any damaged wiring or connectors, updating software, or replacing the control module if necessary.

6. Is the U12A4 code a serious issue that needs immediate attention?

- While it may not cause immediate harm to your vehicle, addressing the U12A4 code promptly is recommended to prevent any potential long-term issues with engine performance and emissions.

7. Can a DIY enthusiast fix the U12A4 code issue?

- Depending on your skill level and access to tools, some DIY enthusiasts may be able to diagnose and repair the U12A4 code themselves, especially if it involves simple tasks like replacing a sensor or checking wiring.

8. How much does it typically cost to repair the U12A4 code in a Chrysler vehicle?

- The cost of repairing the U12A4 code can vary depending on the exact cause of the issue, but it may range from $100 to $500 or more, including parts and labor.

9. Will resetting the trouble codes make the U12A4 code disappear permanently?

- Simply resetting the trouble codes may temporarily clear the U12A4 code, but it's important to diagnose and address the underlying issue to prevent it from reoccurring.

10. Are there any recalls or technical service bulletins related to the U12A4 code in Chrysler vehicles?

- It's recommended to check with your local Chrysler dealership or visit the NHTSA website to see if there are any recalls or technical service bulletins related to the U12A4 code in your specific vehicle model.