P0746 on 2020-2024 Cadillac XT5: Snap Ring Failure, Causes, and Fixes

What's Unique About the 2020-2024 Cadillac XT5

The Cadillac XT5 uses a GM 9T-series automatic transmission (specifically the 9T65, RPO code M3W). For this transmission family, code P0746 is strongly linked to a specific, documented mechanical failure. Manufacturer Technical Service Bulletin (TSB) #PIP5974E reveals that out-of-round snap rings within the 1-2-3-4-5-6 clutch assembly are a primary cause. This defect is particularly prevalent in transmissions built between October 1, 2023, and April 22, 2024 (Julian dates 23274 to 24113). 🎬 Watch: Why this specific manufacturing defect is so dangerous. This internal failure can lead to a complete loss of movement, making it a much more severe issue than a simple solenoid swap. Ignoring this known mechanical issue and replacing only the solenoid will not fix the root problem, a mistake the TSB explicitly warns against.

Diagnostic Flowchart

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

Symptoms You May Notice

• Vehicle will not move when in Drive or Reverse.
• Harsh, delayed, or erratic shifting.
• Transmission slipping or getting stuck in one gear.
• Check Engine Light or Malfunction Indicator Lamp is illuminated.
• Transmission may enter "limp mode" with reduced functionality.
• Increased fuel consumption.

Most Likely Causes

1. Internal Transmission Snap Ring Failure 🔴 High Probability → Shop Transmission Assembly As documented in GM TSB #PIP5974E, the '(594) 1-2-3-4-5-6 Clutch Spring Retaining Ring' or '(599) 1-2-3-4-5-6 Clutch Backing Plate Retaining Ring' can be out of round. This is a known manufacturing defect on the 9T-series transmission, especially those with a Julian build date between 23 274 and 24 113 (Oct 2023 - Apr 2024).
   How to confirm: The primary method is checking the transmission's Julian build date. If it falls within the affected range, this is the most likely cause. Otherwise, confirmation requires transmission disassembly and inspection of the clutch pack and snap rings. 🎬 See a teardown of a 9T65 with no movement. Debris in the transmission pan is a strong indicator.
   Typical fix: The transmission must be removed and disassembled. Per TSB PIP5974E, the fix involves replacing the entire 1-2-3-4-5-6 clutch piston housing assembly, clutch plates, seals, and the faulty snap rings. The TSB explicitly warns *not* to replace the valve body or solenoids for this issue.
   Est. part cost: $200-$500 for the full clutch piston housing, seals, and snap ring kit, but often part of a larger rebuild kit.
2. Low or Contaminated Transmission Fluid 🟡 Medium Probability → Shop Transmission Assembly
   How to confirm: Check the transmission fluid level and condition per the service procedure. Fluid should be at the correct level, red, and not smell burnt. Dark, dirty, or metallic fluid can indicate internal damage (like from a failing snap ring) and clog passages or solenoids.
   Typical fix: Perform a transmission fluid and filter change using the manufacturer-specified fluid (ACDelco DEXRON ULV). If the fluid is very contaminated, this is likely a symptom of the snap ring failure and a fluid change alone will not solve the problem.
   Est. part cost: $150-$250 for fluid and filter.
3. Failed Pressure Control Solenoid 'A' ⚪ Low Probability → Shop Transmission Valve Body On this platform, the solenoid is rarely the root cause. TSBs specifically warn against replacing it if snap ring failure is suspected.
   How to confirm: A technician can use a professional scan tool to monitor the solenoid's commanded state vs. its actual performance. The solenoid's resistance can also be checked with a multimeter 🎬 Watch: Understanding how P0746 relates to solenoid pressure. to see if it's within specification. However, these tests can be misleading if the underlying issue is a mechanical pressure loss.
   Typical fix: Replace the pressure control solenoid. This is located inside the transmission on the valve body. This repair should only be attempted after definitively ruling out the snap ring failure.
   Est. part cost: $100-$250

Rare But Worth Checking

• Faulty Transmission Control Module (TCM) or Wiring: → Shop Transmission Assembly While less common than the mechanical snap ring failure, electrical issues like a corroded connector, damaged wire, or a faulty TCM can prevent the solenoid from being controlled correctly, triggering a P0746 code.
• Clogged Transmission Filter or Passages: → Shop Transmission Assembly Debris from normal wear or a failing component (like the snap ring) can clog the transmission filter or internal hydraulic passages, restricting fluid flow and causing pressure-related codes.
• Solenoid Retaining Clip Fatigue: On some GM multi-speed transmissions, the clips holding the solenoids in the valve body can fatigue. This allows the solenoid to be pushed partially out of its bore, creating a hydraulic leak and causing performance codes like P0746.

Diagnosis Steps

1. Verify the code with a professional OBD-II scanner.
2. Check the transmission fluid level and condition. Low or burnt fluid is an immediate red flag for internal damage.
3. Check the transmission's Julian build date. If it falls between 23 274 and 24 113 (Oct 2023 - Apr 2024), the snap ring failure is highly probable.
4. Review all available Technical Service Bulletins (TSBs) for the vehicle, paying close attention to PIP5974E, PIE0720A, and PIE0720.
5. Use a scan tool to monitor live transmission data, including line pressure and the commanded state of Pressure Control Solenoid 'A'.
6. If fluid is okay and the build date is outside the TSB range, test the solenoid's circuit for continuity and proper voltage from the TCM.
7. Given the high probability of the snap ring issue, if other tests do not find a fault, internal transmission inspection is the next logical step. Look for metal debris in the pan.

Parts You'll Likely Need

• 1-Reverse and 1-2-3-4-5-6 Clutch Piston Housing Assembly — This is the core of the repair specified in TSB PIP5974E. The original housing may be damaged when the snap ring dislodges. The TSB calls for replacing the housing and all related clutch components as a unit.
  Trusted brands: GM Genuine Parts
  OEM price range: $200-$400
  Aftermarket price range: N/A
• Transmission Snap Ring & Clutch Kit (OEM #e.g., 24260139 (example kit, not specific to this clutch)) — This is the root cause of the problem. TSB PIP5974E requires replacing the '(594) Clutch Spring Retaining Ring' and '(599) Clutch Backing Plate Retaining Ring' along with all clutch plates (wave, friction, backing) and seals.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $100-$250
  Aftermarket price range: $50-$150
• Transmission Fluid (DEXRON ULV) — Required for refilling the transmission after a full rebuild.
  Trusted brands: ACDelco
  OEM price range: $20-$30 per quart
  Aftermarket price range: $15-$25 per quart

Related Codes That Often Appear With This One

• P0747 — This code for 'Pressure Control Solenoid 'A' Stuck On' is the direct counterpart to P0746. Both codes are mentioned together in the NHTSA TSBs (PIP5974E, PIE0720A) and relate to the same internal snap ring failure.

Technical Service Bulletins (TSBs) & Recalls

• PIP5974E: Communicates that out-of-round transmission snap rings can cause code P0746 or P0747. It provides a specific date range for affected transmissions and a detailed list of parts to replace, warning against replacing the valve body.
• PIE0720A: Mentions DTCs P0746 and P0747 in relation to a vehicle that will not move in Drive or Reverse.
• PIE0720: Precursor to PIE0720A, requesting information from technicians about the no-move condition associated with P0746/P0747.

Platform-Specific Known Issues

• A known issue, documented in TSB #PIP5974E, points to 'transmission 1-2-3-4-5-6 snap rings out of round' as a direct cause for code P0746.
• TSBs #PIE0720A and #PIE0720 confirm that this code can lead to a severe 'Vehicle Will Not Move' condition, highlighting the seriousness of the underlying fault.
• A specific batch of transmissions built between October 2023 and April 2024 are identified in TSBs as being particularly prone to this failure.

Mechanic-Grade Diagnostic Values

• Pressure Control Solenoid (PWM Type) Resistance — expected: 3-8 Ohms. Failure: A reading of 0 Ohms indicates a short, while infinite resistance (OL) indicates an open circuit. Readings outside the expected range suggest a faulty solenoid coil.
• Shift Solenoid (On/Off Type) Resistance — expected: 20-40 Ohms. Failure: Readings significantly outside this range, or showing open/shorted, indicate a failed solenoid.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Solenoid Valve Diagnosis / Bidirectional Control — After checking fluid and TSBs, a technician can use this function to command each solenoid on and off to check for an audible click. For P0746, the technician would command the 1-2-3-4-5-6 clutch solenoid (Solenoid B) and listen for a response. This helps determine if the solenoid is electrically responsive, though it cannot confirm correct hydraulic pressure or rule out a mechanical blockage.
• GDS2 (GM Global Diagnostic System 2): Garage Shift Test — This automated test, referenced in GM diagnostic procedures, cycles the solenoids to help flush debris and verify engagement. For a P0746, running this test while monitoring shift data can help confirm if the 1-2-3-4-5-6 clutch is failing to apply as commanded.

Wiring & Ground Locations

• Transmission Case Connector Pin 1 — The main 14-pin electrical connector on the transmission case.. Pin 1, with a Blue wire, is the control circuit for the 'Transmission Control Solenoid B (1) (1-2-3-4-5-6 Clutch)'. A technician would test this pin for continuity, shorts to ground, or voltage signals from the TCM to diagnose electrical faults in the solenoid circuit before condemning the internal transmission components.
• TCM Ground — The Transmission Control Module (TCM) is mounted on the valve body side cover inside the transmission. Its ground path is through the transmission case itself, which is then grounded to the chassis and engine block via ground straps.. A poor ground connection between the engine/transmission and the chassis can cause erratic behavior in all transmission electronics, including solenoids. While not a primary cause for this specific TSB-related issue, checking the main engine-to-chassis ground straps is a fundamental step in any electrical diagnosis.

OEM Part Supersession History

• Unknown → 24293353 (and others) — The TSB PIP5974E repair requires replacing the entire '(590)1-Reverse and 1-2-3-4-5-6 Clutch Piston Housing' assembly. While a direct supersession trail for the faulty snap ring is not public, the existence of complete replacement clutch housing assemblies like P/N 24293353 suggests an updated or complete unit is the intended fix.

Model Year Variations Within This Range

• 2020-2023: For vehicles with low mileage (<12,000 miles) experiencing various transmission DTCs, GM ran a '9T65 Transmission Replacement Pilot Program' which ended in September 2021. Under this program, some transmissions were replaced as complete assemblies rather than repaired. Post-program, diagnostic and repair strategies were updated based on teardown findings, with bulletin 20-NA-136 providing guidance on when to replace the valve body vs. the entire unit for other codes.