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2019 CT6 Transmission Shifting Hard & Limp Mode - P0700

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Emily N. · rep 0 · May 22, 3:56 AM · 1 replies · solved · Question

Vehicle: 2019 Cadillac CT6 Platinum

My 2019 Cadillac CT6 Platinum with the 3.0TT engine has been acting up lately. It started shifting really hard, especially between 2nd and 3rd gear, and sometimes it feels like it's getting stuck in a gear. Today, the Check Engine Light came on, and the car went into what feels like 'limp mode' – very limited power and won't shift past a certain gear.

I pulled the code, and it's P0700, which I know is a generic transmission control system malfunction. I'm worried this is going to be an expensive fix. Has anyone experienced this with their CT6? What was the underlying cause?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:56 AM

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ClearTheCode admin answer:

The P0700 code on your 2019 Cadillac CT6 Platinum indicates that the Transmission Control Module (TCM) has detected a fault within the transmission system and has illuminated the Check Engine Light. This code is a general indicator, meaning there will be other, more specific transmission-related codes stored in the TCM that provide more detail.

Limp mode is a protective measure taken by the vehicle's computer to prevent further damage to the transmission when a serious fault is detected.

Common causes for hard shifting and limp mode with a P0700 code include:

  1. Low or Contaminated Transmission Fluid: Insufficient fluid levels or old, burnt fluid can cause pressure issues and affect shifting. Check the fluid level (if accessible) and condition. Note that many modern transmissions are sealed and require specific procedures for checking/filling.
  2. Faulty Transmission Solenoids: Solenoids control the flow of transmission fluid to engage different gears. If one or more solenoids are sticking or failing, it can lead to hard shifts, delayed engagement, or gears getting stuck.
  3. Valve Body Issues: The valve body is the hydraulic control center of the transmission. Problems within the valve body, such as worn passages or stuck valves, can severely impact shifting performance.
  4. Transmission Speed Sensors: Input or output speed sensors provide crucial data to the TCM. If these sensors are faulty, the TCM won't know the correct transmission speed, leading to incorrect shift points or limp mode.
  5. TCM Malfunction: While less common, the Transmission Control Module itself can fail, leading to a wide range of shifting problems.
  6. Internal Transmission Mechanical Failure: In more severe cases, internal components like clutch packs or gears could be worn or damaged.

When to See a Shop:

  • Immediately, as driving in limp mode for extended periods can cause further damage. A professional diagnosis is crucial.
  • A specialized transmission shop or Cadillac dealership will have the advanced diagnostic tools to read the specific transmission fault codes (P07xx codes) stored in the TCM, which are necessary to pinpoint the exact issue. They can also perform fluid pressure tests and inspect internal components if needed.
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