Engine-CodesGMC – P189C 2018 GMC Sierra

P189C 2018 GMC Sierra Code - Transmission Range Command Message Performance

Quick Answer

The P189C diagnostic trouble code (DTC) for a 2018 GMC Sierra relates to the Transmission Range Command Message Performance. Common causes include Faulty wiring or connectors, Loose connections between TCM and ECM, Malfunctioning transmission range sensor. 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
P189C 2018 GMC Sierra indicates Transmission Range Command Message Performance.
Common causes
Common causes include Faulty wiring or connectors, Loose connections between TCM and ECM, Malfunctioning transmission range sensor.
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.
Table of contents Created and updated by William Orellana on Sep 17, 2024
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Code P189C 2018 GMC Sierra Description

The P189C diagnostic trouble code (DTC) for a 2018 GMC Sierra relates to the Transmission Range Command Message Performance. This code indicates that there is an issue with the communication between the transmission control module (TCM) and the engine control module (ECM) regarding the transmission range command. The transmission range command message is crucial for the proper operation of the transmission, as it informs the TCM about the current gear selection and allows the TCM to make necessary adjustments for smooth shifting and overall performance.

OBDII Code P189C 2018 GMC Sierra - Transmission Range Command Message Performance
P189C 2018 GMC Sierra Code - Transmission Range Command Message Performance

Common Causes of P189C 2018 GMC Sierra

  1. Faulty wiring or connectors
  2. Loose connections between TCM and ECM
  3. Malfunctioning transmission range sensor
  4. Defective TCM or ECM
  5. Software issues in the TCM or ECM

Symptoms of P189C 2018 GMC Sierra

  1. Harsh or delayed shifting
  2. Erratic transmission behavior
  3. Slipping gears
  4. Loss of transmission function
  5. Illumination of the Check Engine Light

How to Fix P189C 2018 GMC Sierra

  1. Begin by using a diagnostic scanner to retrieve the trouble codes and perform a thorough inspection of the transmission system.
  2. Check the wiring and connectors for any signs of damage or corrosion. Repair or replace as needed.
  3. Inspect the transmission range sensor and ensure it is functioning correctly. Replace if necessary.
  4. Verify the communication between the TCM and ECM by performing a relearn procedure or updating the software.
  5. Clear the DTC and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P189C 2018 GMC Sierra

The typical repair costs for addressing the P189C code on a 2018 GMC Sierra can vary depending on the exact cause of the issue. On average, the parts and labor for this repair may range from $200 to $500. However, it's important to note that specific diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. It's advisable to check with local repair shops for a more accurate estimate.

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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 P189C 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code P189C in a 2018 GMC Sierra?

- Common symptoms include harsh shifting, transmission slipping, and the inability to shift gears smoothly.

2. What are the possible causes of OBDII code P189C in a 2018 GMC Sierra?

- Possible causes may include a faulty transmission range sensor, damaged wiring or connectors, or issues with the transmission control module.

3. How can I diagnose the OBDII code P189C in my 2018 GMC Sierra?

- Diagnosing this code typically involves using a scan tool to retrieve the specific fault codes and checking the transmission range sensor for proper operation.

4. Is it safe to continue driving my 2018 GMC Sierra with OBDII code P189C present?

- It is not recommended to continue driving with this code present, as it can lead to further damage to the transmission and potentially cause safety hazards.

5. Can I reset the OBDII code P189C in my 2018 GMC Sierra myself?

- While you can clear the code with a scan tool, it is essential to address the underlying issue causing the code to prevent it from reoccurring.

6. How much does it typically cost to repair OBDII code P189C in a 2018 GMC Sierra?

- The cost of repair can vary depending on the exact cause of the code, but it may range from a simple sensor replacement to more extensive transmission repairs.

7. Are there any DIY tips for fixing OBDII code P189C in a 2018 GMC Sierra?

- DIY tips may include checking and cleaning the transmission range sensor connectors, inspecting for damaged wiring, and ensuring proper transmission fluid levels.

8. Will OBDII code P189C in my 2018 GMC Sierra affect fuel efficiency?

- Yes, this code can affect fuel efficiency as it may lead to improper shifting and increased strain on the transmission components.

9. How long does it typically take to repair OBDII code P189C in a 2018 GMC Sierra?

- The repair time can vary depending on the exact cause of the code and the complexity of the repair, but it may range from a few hours to a full day.

10. Can a regular mechanic fix OBDII code P189C in a 2018 GMC Sierra, or is a specialized technician required?

- A regular mechanic with experience in diagnosing and repairing transmission issues should be able to address OBDII code P189C in a 2018 GMC Sierra.

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