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Engine-Codes – Generic – P189A

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

Quick Answer

The P189A diagnostic trouble code (DTC) indicates that there is an issue with the Four Wheel Drive (4WD) system, specifically related to the secondary signal message counter. Common causes include Faulty or damaged 4WD control module, leading to incorrect signal processing, Wiring issues, such as short circuits or corrosion, affecting communication between modules, Malfunctioning sensors that provide feedback to the control modules, resulting in inaccurate data. 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 indicates Four Wheel Drive Range Secondary Signal Message Counter Incorrect.
Common causes
Common causes include Faulty or damaged 4WD control module, leading to incorrect signal processing, Wiring issues, such as short circuits or corrosion, affecting communication between modules, Malfunctioning sensors that provide feedback to the control modules, resulting in inaccurate data.
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 Description

The P189A diagnostic trouble code (DTC) indicates that there is an issue with the Four Wheel Drive (4WD) system, specifically related to the secondary signal message counter. This code is typically triggered when the vehicle's onboard computer detects an inconsistency in the expected communication between the 4WD control module and other related systems, such as the transmission control module or the engine control module.

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

Common Causes of P189A

  1. Faulty or damaged 4WD control module, leading to incorrect signal processing.
  2. Wiring issues, such as short circuits or corrosion, affecting communication between modules.
  3. Malfunctioning sensors that provide feedback to the control modules, resulting in inaccurate data.
  4. Software glitches or outdated firmware in the vehicle's control modules that need to be updated or reset.
  5. Mechanical issues within the transfer case or differential that may interfere with proper operation.

Symptoms of P189A

  1. Inconsistent engagement of the 4WD system, with difficulty switching between modes.
  2. Warning lights illuminated on the dashboard, specifically related to the 4WD system.
  3. Unusual noises from the drivetrain when attempting to engage 4WD.
  4. Decreased traction or stability in slippery conditions, indicating potential failure of the 4WD system.
  5. Transmission shifting issues, such as harsh or delayed shifts, which may be related to the 4WD system's malfunction.

How to Fix P189A

  1. Diagnostic Scan: Begin with a thorough diagnostic scan to confirm the P189A code and check for any additional codes that may provide more context.
  2. Visual Inspection: Conduct a visual inspection of the wiring and connectors associated with the 4WD system for signs of damage, corrosion, or loose connections.
  3. Sensor Testing: Test the 4WD sensors for proper operation and replace any that are found to be faulty.
  4. Control Module Update: If applicable, update the software or firmware of the 4WD control module to ensure it is functioning with the latest programming.
  5. Component Replacement: If the control module or any other components are found to be defective, replace them and clear the codes to see if the issue is resolved.

Cost to Fix P189A

The cost to repair 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 repairs, which may include parts and labor. This estimate can include costs for replacing sensors, control modules, or wiring repairs. Labor rates typically range from $80 to $150 per hour, depending on the location, vehicle make and model, and engine type. In metropolitan areas or at dealerships, rates may be higher, while independent shops may offer lower rates. It's advisable to check local rates for a more precise estimate tailored to your specific situation.

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Code P189A Information for Specific Makes

  • P189A Chevrolet — Four Wheel Drive Range Secondary Signal Message Counter Incorrect
  • P189A GMC — Four Wheel Drive Range Secondary Signal Message Counter Incorrect
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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