AutoCodes – Jeep – U12A4 Jeep

U12A4 Jeep 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 Jeep 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 528

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

What does this mean?

What are the Possible Causes of the DTC U12A4 Jeep?

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 Jeep?

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 Jeep 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 U12A4 Jeep code?

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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 Jeep Code

1. What does the OBDII code U12A4 for Jeep mean?

The code U12A4 indicates a lost communication issue with the ammonia sensor in your Jeep.

2. What are the common symptoms of a U12A4 code in a Jeep?

Common symptoms include the check engine light coming on, poor engine performance, and potential difficulty starting the vehicle.

3. What are some possible causes of a U12A4 code in a Jeep?

Potential causes include a faulty ammonia sensor, damaged wiring or connectors related to the sensor, or a communication error within the vehicle's system.

4. How serious is a U12A4 fault code in a Jeep?

While the vehicle may still be operable with this code, it is important to address it promptly to prevent any potential long-term damage to the vehicle's emissions system.

5. Can I continue driving my Jeep with a U12A4 code?

It is generally not recommended to continue driving the vehicle with a U12A4 code present, as it can affect the vehicle's performance and emissions.

6. How can I diagnose a U12A4 code in my Jeep?

Diagnosing the issue typically involves using a diagnostic scanner to read the code and potentially checking the ammonia sensor and related components for any visible damage.

7. What are some repair tips for fixing a U12A4 code in a Jeep?

Repair tips may include checking and repairing any damaged wiring or connectors, replacing the ammonia sensor if necessary, and clearing the code to see if the issue persists.

8. Can I reset the U12A4 code in my Jeep without fixing the underlying issue?

While you can clear the code with a diagnostic scanner, it is essential to address the root cause of the problem to prevent the code from reoccurring.

9. Is it possible to prevent a U12A4 code from appearing in my Jeep?

Regular vehicle maintenance, including checking the condition of sensors and related components, can help prevent issues that may trigger a U12A4 fault code.

10. Should I seek professional help to fix a U12A4 fault code in my Jeep?

If you are not comfortable diagnosing or repairing the issue yourself, it is advisable to seek assistance from a qualified mechanic or dealership to address the U12A4 fault code effectively.