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P1899 2018 GMC Sierra Code - Axle Torque Secondary Signal Message Counter Incorrect

Quick Answer

The P1899 code indicates a problem with the axle torque secondary signal message counter in GMC vehicles. Common causes include Faulty axle torque sensor that is providing incorrect readings, Damaged or corroded wiring/connectors affecting signal transmission, Malfunctioning 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
P1899 2018 GMC Sierra indicates Axle Torque Secondary Signal Message Counter Incorrect.
Common causes
Common causes include Faulty axle torque sensor that is providing incorrect readings, Damaged or corroded wiring/connectors affecting signal transmission, Malfunctioning 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 P1899 2018 GMC Sierra Description

The P1899 code indicates a problem with the axle torque secondary signal message counter in GMC vehicles. This code is part of the vehicle's onboard diagnostics (OBD-II) system and is specifically related to the communication between the transmission control module (TCM) and the engine control module (ECM). The axle torque secondary signal is crucial for the vehicle's performance, as it helps the TCM determine the appropriate shift points and optimize power delivery to the wheels. When the message counter is deemed incorrect, it suggests that the TCM is not receiving accurate information about the axle torque, which can lead to improper transmission behavior.
OBDII Code P1899 2018 GMC Sierra - Axle Torque Secondary Signal Message Counter Incorrect
P1899 2018 GMC Sierra Code - Axle Torque Secondary Signal Message Counter Incorrect

Common Causes of P1899 2018 GMC Sierra

  1. Faulty axle torque sensor that is providing incorrect readings.
  2. Damaged or corroded wiring/connectors affecting signal transmission.
  3. Malfunctioning transmission control module (TCM).
  4. Software issues within the TCM that require reprogramming or updates.
  5. Mechanical issues within the transmission affecting torque measurement.

Symptoms of P1899 2018 GMC Sierra

  1. Erratic or harsh shifting during acceleration or deceleration.
  2. Decreased fuel efficiency due to improper transmission operation.
  3. Transmission slipping or failing to engage properly.
  4. Illuminated check engine light on the dashboard.
  5. Unusual noises from the transmission, such as grinding or whining.

How to Fix P1899 2018 GMC Sierra

  1. Diagnostic Testing: Begin with a thorough diagnostic scan to confirm the P1899 code and check for any additional codes that may provide insight into related issues.
  2. Inspect Wiring and Connectors: Examine the wiring harness and connectors associated with the axle torque sensor for any signs of damage, corrosion, or loose connections. Repair or replace as necessary.
  3. Test the Axle Torque Sensor: Use a multimeter or scan tool to test the axle torque sensor's output. If the sensor is found to be faulty, replace it with a new one.
  4. Check Transmission Control Module: If the sensor and wiring are in good condition, the issue may lie within the TCM itself. Consider reprogramming or replacing the TCM if necessary.
  5. Road Test: After repairs, perform a road test to ensure that the transmission is shifting smoothly and that the P1899 code does not reappear.

Cost to Fix P1899 2018 GMC Sierra

Repair costs for the P1899 code can vary widely based on the specific diagnosis and repairs needed. On average, you can expect to pay between $200 to $800 for repairs, which may include parts and labor. For instance, replacing an axle torque sensor may cost around $100 to $300, while more extensive repairs involving the TCM could range from $500 to $1,200. It's important to note that labor rates at auto repair shops typically range from $80 to $150 per hour, depending on location, vehicle make and model, and engine type. In metropolitan areas or at dealerships, rates may be higher, while independent shops often charge less. Therefore, it's advisable to check local rates for a more precise estimate tailored to your specific situation.

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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.

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