how to fix P0700 transmission code in GMC Sierra T1XX (2019-Present)

Learn how to diagnose and fix P0700 transmission fault in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface, and the engine is off.
• Disconnect the battery negative terminal to ensure safety.

2. Inspect and Replace Transmission Fluid

• Sub-steps:
  • Remove the transmission fluid dipstick and check fluid level.
  • If fluid is low, add the recommended type (Dexron VI for GMC Sierra).
  • If fluid is contaminated, drain and replace the fluid.
• Tools Required: Transmission fluid pump, funnel, drain pan.
• Safety Warnings: Always allow the engine to cool before working on the transmission.

3. Check and Repair Wiring and Connectors

• Sub-steps:
  • Visually inspect wiring harness leading to the TCM for frays or damage.
  • Disconnect connectors and clean them with electrical contact cleaner.
  • Repair or replace any damaged wiring or connectors.
• Tools Required: Wire strippers, soldering kit, electrical contact cleaner.

4. Replace Transmission Control Module (if necessary)

• Sub-steps:
  • Remove the TCM from its mounting location.
  • Disconnect the wiring harness from the TCM.
  • Install the new TCM by connecting the wiring harness and securing it in place.
• Tools Required: Socket set, torque wrench.
• Safety Warnings: Ensure all electrical connections are secure to prevent future faults.

5. Reconnect Battery and Test Drive

• Sub-steps:
  • Reconnect the battery terminal.
  • Start the vehicle and allow it to reach operating temperature.
  • Test drive the vehicle to ensure the transmission shifts smoothly and the check engine light is off.
• Tools Required: OBD-II scanner for code clearing.