why does my GMC Sierra T1XX (2019-Present) have a delay when shifting gears?

Learn how to diagnose and fix transmission delay issues in GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms, diagnostics, and repair instructions.

Solution

1. Preparation

• Ensure the vehicle is on a level surface and engage the parking brake.
• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent any electrical issues.

2. Check and Replace Transmission Fluid

• Sub-steps:
  1. Locate the transmission dipstick and remove it to check fluid level.
  2. If low, add the appropriate type of transmission fluid (consult owner's manual for specifications).
  3. If fluid is discolored or burnt, drain the transmission fluid using a drain pan.
  4. Replace with new transmission fluid, ensuring to use the correct OEM specification.
• Tools Required: Fluid pump, drain pan, funnel.
• Safety Warnings: Allow the engine to cool before checking fluid levels to avoid burns.

3. Inspect and Repair Transmission Control Module (TCM)

• Sub-steps:
  1. Remove the TCM from its housing by disconnecting the electrical connectors and unbolting it.
  2. Inspect for any visible damage or corrosion on the connectors.
  3. Clean the connectors with electrical contact cleaner.
  4. If TCM is faulty, replace it with a new unit and reassemble.
• Tools Required: Socket set, electrical contact cleaner.

4. Update Transmission Software

• Sub-steps:
  1. Using a professional-grade scan tool, connect to the vehicle’s OBD-II port.
  2. Check for available software updates from GMC and follow the prompts to install any necessary updates.
  3. Clear any fault codes present in the system after the update.
• Tools Required: Professional OBD-II scanner with update capability.