my GMC Sierra T1XX (2019-Present) has a check engine light with code P0700

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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Check and Replace Transmission Fluid

• Tools required: Transmission fluid pump, socket set, fluid catch pan
• Remove the transmission fluid pan bolts using a socket set.
• Carefully lower the pan and allow old fluid to drain into the catch pan.
• Inspect the pan for metal shavings or debris that could indicate internal damage.
• Replace the transmission filter if applicable.
• Reinstall the pan with a new gasket and torque the bolts to the manufacturer's specifications.
• Refill the transmission with the correct type and amount of fluid as specified in the owner's manual.

3. Inspect and Repair TCM Connections

• Tools required: Multimeter, wire stripper/crimper
• Inspect the wiring harness connected to the TCM for any frayed wires or corrosion.
• Use a multimeter to test continuity and ensure proper voltage is reaching the TCM.
• Repair any damaged wiring or connectors.
• Reconnect the TCM and ensure it is securely mounted.

4. Reprogram TCM (if necessary)

• Tools required: OBD-II scanner with programming capability
• Follow the manufacturer's instructions to reprogram the TCM if a fault was found that required a reset.
• Clear all DTCs using the OBD-II scanner.

5. Final Checks

• Reconnect the negative battery terminal.
• Start the engine and check for any warning lights.
• Perform a road test to ensure the transmission is functioning correctly and no DTCs are present.