what does it mean when my GMC Sierra T1XX (2019-Present) shows a P0700 code?

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 necessary tools and safety gear.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Fluid Inspection

• Remove the transmission dipstick and check fluid level.
• If low, add the correct type of transmission fluid as per manufacturer specifications.
• If fluid is discolored or has a burnt smell, plan for a transmission fluid change.

3. TCM Inspection

• Locate the TCM (typically near the transmission or under the dashboard).
• Inspect the TCM for any physical damage or signs of overheating.
• Check all electrical connections to ensure they are secure and free from corrosion.

4. Electrical Testing

• Using a multimeter, check for incoming power and ground to the TCM.
• If voltage is absent, trace wiring back to the battery and ignition circuit.
• If voltage is present, proceed to test the TCM output signals to the transmission solenoids.

5. TCM Replacement (if necessary)

• If the TCM is faulty, remove it by disconnecting wiring harness and unbolting it from the mounting location.
• Install the new TCM by reversing the removal steps, ensuring all connections are secure.
• Reconnect the negative battery terminal.

6. Fluid Change (if necessary)

• If the fluid was contaminated, drain the old transmission fluid completely.
• Replace the transmission filter if applicable.
• Refill with the recommended amount of new transmission fluid.