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P189A Chevrolet Code - Four Wheel Drive Range Secondary Signal Message Counter Incorrect

Quick Answer

The P189A code indicates that there is a discrepancy in the secondary signal message counter for the four-wheel-drive (4WD) system in Chevrolet vehicles. Common causes include Faulty or malfunctioning 4WD range sensors, Damaged or corroded wiring and connectors related to the 4WD system, Software issues within the transmission control module (TCM). 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
P189A Chevrolet indicates Four Wheel Drive Range Secondary Signal Message Counter Incorrect.
Common causes
Common causes include Faulty or malfunctioning 4WD range sensors, Damaged or corroded wiring and connectors related to the 4WD system, Software issues within the transmission control module (TCM).
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.
What is this?
Table of contents Created and updated by William Orellana on Jun 18, 2025
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Code P189A Chevrolet Description

The P189A code indicates that there is a discrepancy in the secondary signal message counter for the four-wheel-drive (4WD) system in Chevrolet vehicles. This code is typically triggered when the transmission control module (TCM) detects that the signal messages related to the 4WD range are not aligning with expected values. The 4WD system relies on a series of sensors and control modules to communicate effectively, ensuring that the vehicle can transition between different drive modes (e.g., 2WD, 4WD High, 4WD Low) seamlessly.
OBDII Code P189A Chevrolet - Four Wheel Drive Range Secondary Signal Message Counter Incorrect
P189A Chevrolet Code - Four Wheel Drive Range Secondary Signal Message Counter Incorrect

Common Causes of P189A Chevrolet

  1. Faulty or malfunctioning 4WD range sensors.
  2. Damaged or corroded wiring and connectors related to the 4WD system.
  3. Software issues within the transmission control module (TCM).
  4. Mechanical failure within the transfer case or transmission.
  5. Poor communication between the TCM and other control modules due to a network issue.

Symptoms of P189A Chevrolet

  1. Inability to engage or disengage 4WD modes.
  2. Erratic or harsh shifting while changing between drive modes.
  3. Warning lights illuminated on the dashboard, particularly the 4WD indicator.
  4. Unusual noises coming from the transfer case or transmission during operation.
  5. Decreased traction or stability in conditions requiring 4WD engagement.

How to Fix P189A Chevrolet

  1. Diagnostic Scan: Begin by using an OBD-II scanner to confirm the P189A code and check for any additional codes that may provide further insight into the issue.
  2. Visual Inspection: Inspect the wiring and connectors associated with the 4WD system for signs of damage, corrosion, or loose connections.
  3. Sensor Testing: Test the 4WD range sensors for proper operation and replace any that are found to be faulty.
  4. TCM Reprogramming: If the TCM is suspected to be the issue, consider reprogramming or updating the software to ensure it is functioning correctly.
  5. Mechanical Inspection: If all electrical components are functioning properly, conduct a thorough inspection of the transfer case and transmission for any mechanical failures that may be contributing to the problem.

Cost to Fix P189A Chevrolet

Repair costs for addressing the P189A code can vary widely based on the specific diagnosis and repairs needed. On average, you might expect to pay between $200 and $800 for parts and labor. This estimate includes potential sensor replacements, wiring repairs, or TCM reprogramming. Labor rates typically range from $80 to $150 per hour, depending on the location and type of repair shop. In metropolitan areas or at dealerships, rates may be higher, while independent shops often offer more competitive pricing. It is advisable to check with local repair shops for a more precise estimate based on your vehicle's specific needs and the prevailing labor rates in your area.

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Information for Specific Chevrolet Models

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.

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