P0747 on 2020-2024 Cadillac CT5: Causes, Symptoms, and Fixes

What's Unique About the 2020-2024 Cadillac CT5

The 2020-2024 Cadillac CT5, along with other GM vehicles using the 10-speed automatic transmission, has a known issue with this code. The problem is rarely the solenoid itself. Instead, wear within the transmission control valve body, specifically in the aluminum 'feed limit low valve' bore, causes a loss of hydraulic pressure that triggers the P0747 code. This issue is so well-documented that GM has issued multiple service bulletins (like #24-NA-088) and a Special Coverage program (#N242480631) to address it, often following a previous software update (N242480630) intended to detect the wear. More recent bulletins (like #25-NA-255) have even introduced a procedure to repair the valve body with an updated steel valve and stronger spring 🎬 Watch: A breakdown of GM's new steel valve repair kit. instead of full replacement.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Malfunction Indicator Lamp (MIL) or Check Engine Light is on.
• Harsh, jerky, or slamming gear shifts.
• Transmission is stuck in a single gear (often 5th gear) and will not shift.
• "Reduced Propulsion" message on the driver information center.
• Delayed engagement when shifting from Park into Drive or Reverse.
• Reduced engine performance.
• In rare, extreme cases, a momentary lock-up of the rear wheels during a downshift.

Most Likely Causes

1. Failed Transmission Control Valve Body 🔴 High Probability → Shop Transmission Valve Body There is a known design issue where the aluminum feed limit low valve bore within the valve body wears prematurely, causing a hydraulic pressure leak. This is a documented pattern failure on GM's 10-speed (10LXX series) transmissions.
   How to confirm: A technician will first check the transmission fluid for level, condition, and signs of excessive clutch material. If the fluid is okay, diagnosis will follow GM's specific procedure outlined in TSB #24-NA-088 or newer bulletins, which point to valve body failure as the primary cause for P0747. The presence of this code after the N242480630 software update is a strong indicator.
   Typical fix: Replace the entire transmission control valve body assembly with the latest superseded part number (Gen-3). An alternative specified in TSB #25-NA-255 for 2021+ models is to repair the existing valve body by installing an updated steel feed limit low valve, a higher tension spring, and a new spacer plate. This repair is only performed if there is no excessive clutch material in the transmission pan.
   Est. part cost: $600-$900
2. Low or Contaminated Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly
   How to confirm: Check the transmission fluid level and condition. The fluid should be at the correct level and not appear dark, burnt, or contain metallic particles. TSB #25-NA-255 states that if excessive clutch material is found, the valve body repair should not be performed and further diagnosis is needed.
   Typical fix: Perform a transmission fluid and filter change. However, if the fluid is burnt or contains significant debris, it indicates a more severe internal problem (like clutch failure) requiring transmission overhaul.
   Est. part cost: $100-$200

Rare But Worth Checking

• Faulty Transmission Control Module (TCM): → Shop Transmission Assembly While possible, a faulty TCM is rare and should only be considered after the valve body and wiring have been thoroughly checked.
• Wiring Harness Damage: Damage to the wiring between the TCM and the transmission valve body could cause this code, but it's much less common than the internal valve body failure.

Diagnosis Steps

1. Verify the code with a professional OBD-II scanner.
2. Check the transmission fluid level and condition. Look for a burnt smell or excessive metallic debris. Per TSB #25-NA-255, if excessive clutch material is found, the valve body is not the root cause and the transmission requires further internal diagnosis.
3. Inspect the transmission wiring harness and connectors for any visible damage, corrosion, or loose connections.
4. Consult GM's service information (IVH) and check for applicable TSBs (like #24-NA-088 or #25-NA-255) or Special Coverage (like #N242480631) for the vehicle's VIN.
5. If fluid and wiring are okay, the primary suspect is the transmission control valve body, as per GM's TSBs.
6. Using a bi-directional scan tool, a technician may command the solenoid on and off to test its response, but this may not pinpoint an internal hydraulic leak within the valve body.
7. Follow the specific repair procedure outlined in the relevant GM service bulletin, which will be either replacing the control valve body assembly or repairing it with updated internal components.

Parts You'll Likely Need

• Transmission Control Valve Body Assembly (OEM #24071206) — This is the most common failure point for code P0747 on this vehicle due to a known issue with internal valve bore wear. This is the latest 'Gen-3' part number which supersedes previous versions like 24065353. 🎬 Watch: Why the Gen-3 valve body is the ultimate fix.
  Trusted brands: ACDelco (OEM)
  OEM price range: $600-$900
  Aftermarket price range: $500-$800

Technical Service Bulletins (TSBs) & Recalls

• 24-NA-088: Addresses customer concerns of MIL illumination and the transmission not shifting, specifically pointing to replacing the transmission control valve body for DTC P0747.
• N242480631-04: A special coverage program for vehicles that experience a P0747 code due to a worn transmission control valve, extending coverage to 15 years/150,000 miles for affected vehicles.
• 25-NA-255: A newer bulletin that instructs technicians to repair the valve body with updated internal components (steel valve, new spring, spacer plate) instead of replacing the entire assembly.

Platform-Specific Known Issues

• GM has issued Special Coverage N242480631 for certain 2020-2021 CT5 models that set a P0747 code after a previous TCM software update (N242480630). This extends the warranty for this specific repair to 15 years or 150,000 miles 🎬 See how this recall fix addresses harsh shifting issues. and covers the replacement of the control valve body.
• TSB #24-NA-088 directly instructs technicians to replace the transmission control valve body to correct a P0747 code that causes the transmission to default to 5th gear.
• A newer TSB, #25-NA-255, outlines a repair procedure for the valve body using an updated steel feed limit valve, spring, and spacer plate, as an alternative to full replacement on some 2021-2024 models.

Mechanic-Grade Diagnostic Values

• Pressure Control Solenoid (PWM type) resistance — expected: 3-8 ohms. Failure: A reading outside this range indicates a faulty solenoid.
• Transmission Line Pressure at idle in Drive — expected: 55-60 psi minimum. Failure: Pressure below this range can prevent diagnostic procedures like the 'Fast Learn' from running and may indicate a hydraulic leak or pump issue.

Hidden / Shadow Codes Worth Checking

• P18A3: This code can set after replacing a Gen-2 valve body with a new Gen-3 unit if the original Park Inhibit Solenoid is not transferred over to the new assembly on vehicles equipped with it. (see via Standard OBD-II scanner after the valve body replacement.)

Scan Tool Commands That Help

• GDS2 / Professional Scan Tool: Transmission Service Fast Learn — This procedure is required after replacing the transmission, valve body, or TCM to allow the module to learn clutch apply pressures. It must be run with the transmission fluid temperature between 167°F-185°F (75°C-85°C).
• GDS2 / Professional Scan Tool: Solenoid Activation Test — To manually command a specific solenoid on and off to check for an audible click or a change in pressure readings. However, this may not detect the internal bore leak common to the P0747 fault.
• N/A - Procedural Note: No Solenoid Characterization / Fast Learn Required — According to TSB #25-NA-255, if only the internal feed limit valve, spring, and spacer plate are replaced (the 'repair kit' fix), the post-repair 'Fast Learn' procedure is NOT required.

Real Owner Repair Stories

• Reddit user 'mxskater' in r/Silverado (Truck with a 10-speed transmission) — Two hard shifts followed by a 'reduced acceleration' message and code P0747.
  ❌ Tried (didn't work) Initial diagnosis was delayed due to the part being back-ordered.
  ✅ What actually fixed it The dealership replaced the transmission control valve body. The repair order cited TSB 24-na-088 and part number 240653536 (likely a typo for 24065353).

OEM Part Supersession History

• 24044192, 24047995 → 24065353 (Gen-2 Valve Body) — Standard part evolution and updates.
• 24065353 (Gen-2 Valve Body) → 24071206 (Gen-3 Valve Body) — Major redesign to improve robustness, consolidate the auxiliary valve body, and relocate solenoids to mitigate known failure patterns.
  Heads up: The Gen-3 valve body uses a different bolt kit (P/N 24073070) which is included with the new part. Old bolts cannot be reused.

Model Year Variations Within This Range

• 2020-2025 (approx.): Vehicles serviced prior to late 2025 likely received a 'Gen-2' valve body (P/N 24065353). Vehicles serviced after received a redesigned 'Gen-3' valve body (P/N 24071206) which consolidated parts, simplified the harness, and relocated solenoids.
• 2021-2024: TSB #25-NA-255 introduced an internal repair kit as an alternative to full valve body replacement for these model years. This suggests 2020 models are more likely to receive a full valve body replacement rather than the internal repair.