P0746 on 2020-2024 GMC Acadia: Pressure Control Solenoid 'A' Causes and Fixes

What's Unique About the 2020-2024 Gmc ACADIA

For this generation of GMC Acadia, which is equipped with a 9-speed automatic transmission (part of the GM 9TXX family), code P0746 is strongly linked to a specific, documented mechanical failure. General Motors has issued multiple Technical Service Bulletins (TSBs) highlighting that the primary cause is often not the solenoid itself, but rather out-of-round or broken snap rings for the 1-2-3-4-5-6 clutch inside the transmission. TSB PIP5974E specifically identifies the '(594) 1-2-3-4-5-6 Clutch Spring Retaining Ring' or the '(599) 1-2-3-4-5-6 Clutch Backing Plate Retaining Ring' as the defective parts. This known issue means the electronic fault code is a symptom of a much more serious internal mechanical problem that requires significant transmission work to correct.

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
• Slipping condition, especially when trying to move from a stop
• Harsh, delayed, or erratic shifting
• Transmission slipping or getting stuck in one gear
• Check Engine Light is on
• Vehicle enters 'Limp Mode' to prevent further damage
• Transmission overheating

Most Likely Causes

1. Internal Transmission Snap Ring Failure 🔴 High Probability → Shop Transmission Assembly Manufacturer TSB #PIP5974E specifically identifies '1-2-3-4-5-6 snap rings out of round' as a direct cause for code P0746 on this platform. Transmissions built between October 2023 and April 2024 are noted as being particularly susceptible.
   How to confirm: This can only be confirmed by disassembling the transmission and visually inspecting the clutch pack snap rings. The TSB explicitly warns technicians *not* to replace the valve body or solenoids as they are not the cause. A key indicator is finding metallic debris in the transmission fluid.
   Typical fix: The transmission must be removed and disassembled to replace the faulty snap rings and any collateral damage. TSB PIP5974E lists a dozen related components that must also be replaced, including the clutch piston housing, seals, clutch plates, and return spring. In many cases, a full transmission rebuild or replacement is the most reliable repair.
   Est. part cost: $100-$5000
2. Failed Pressure Control Solenoid 'A' ⚪ Low Probability → Shop Transmission Valve Body While possible, this is highly unlikely to be the root cause for this specific vehicle and code, due to the known mechanical TSB. The TSB itself warns against replacing the solenoid. Debris from the snap ring failure could damage the solenoid, but the solenoid is not the initial point of failure.
   How to confirm: A technician can use a high-end scan tool to command the solenoid on and off while monitoring pressure data. However, this may be misleading if the underlying hydraulic pressure is lost due to the snap ring failure. Resistance for a PWM solenoid should be between 5 and 30 ohms.
   Typical fix: The solenoid is located inside the transmission on the valve body. It must be accessed by removing the transmission pan and replaced. This repair should only be attempted if the snap ring issue has been definitively ruled out.
   Est. part cost: $120-$250
3. Low or Contaminated Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly
   How to confirm: Check the transmission fluid level and condition. The correct fluid is ACDelco DEXRON VI. Fluid should be bright red and not smell burnt. Dark, brown, or particle-filled fluid is a strong indicator of the internal snap ring wear.
   Typical fix: If low, top off the fluid and inspect for leaks. If contaminated with metallic debris, a fluid change will not fix the problem; it confirms a severe mechanical failure is present and a rebuild is necessary.
   Est. part cost: $50-$200

Rare But Worth Checking

• Faulty Transmission Control Module (TCM): → Shop Transmission Assembly While rare, a faulty TCM can fail to properly command the solenoid or misinterpret sensor data. This should only be considered after all mechanical and wiring issues have been ruled out.
• Clogged Transmission Fluid Passages: → Shop Transmission Assembly Debris from the failing snap ring can clog the fine hydraulic passages within the valve body, preventing the solenoid from controlling pressure even if the solenoid itself is functional. This is a symptom of the mechanical failure, not a root cause.

Diagnosis Steps

1. Verify the code with a professional OBD-II scanner.
2. Check the transmission fluid level and condition. The correct fluid is ACDelco DEXRON VI. Burnt-smelling, dark, or metallic fluid is a strong indicator of the internal snap ring failure. The fluid level must be checked when the transmission fluid temperature (TFT) is between 85–95°C (185–203°F).
3. Check the transmission build date. Per TSB PIP5974A/E, transmissions with Julian dates between 23 274 and 24 113 (roughly Oct 2023 - Apr 2024) are at high risk.
4. Perform a transmission line pressure test at idle. Pressure must be greater than 345 kPa (50 psi). Pressure below this threshold strongly suggests a major internal leak, pump failure, or valve body issue, consistent with the snap ring failure.
5. Use a scan tool to monitor live data, specifically the commanded vs. actual pressure for Pressure Control Solenoid 'A' and the solenoid command status during shifts.
6. Inspect the transmission wiring harness and connectors for any visible damage, corrosion, or loose connections, including main chassis grounds like G401.
7. If the solenoid and its circuit test good, the problem is almost certainly internal to the transmission, pointing towards the known snap ring issue described in TSB #PIP5974E.
8. The final step is transmission removal and disassembly for internal inspection and replacement of the entire 1-2-3-4-5-6 clutch assembly parts as outlined in the TSB.

Parts You'll Likely Need

• Transmission Assembly (OEM #e.g., 24296142, 24296141 (Note: These are examples from used part listings, always verify with VIN)) — Due to the high probability of internal mechanical damage from the known snap ring issue, a complete remanufactured or new transmission is often the most reliable and time-effective repair.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $3500-$5000
  Aftermarket price range: $2500-$4000
• Transmission Snap Ring & Clutch Rebuild Kit — This is the specific component set identified in TSB #PIP5974E as the root cause. A transmission specialist will need to perform a full rebuild, replacing the snap rings, clutch piston housing, clutch plates, seals, and springs.
  Trusted brands: ACDelco
  OEM price range: $200-$500
  Aftermarket price range: $100-$300
• Pressure Control Solenoid 'A' — While very unlikely to be the root cause, the solenoid can be damaged by debris from the primary mechanical failure. It should not be replaced as a first step, per TSB warnings.
  Trusted brands: ACDelco, Bosch
  OEM price range: $150-$250
  Aftermarket price range: $80-$150

Related Codes That Often Appear With This One

• P0747 — This code for 'Pressure Control Solenoid 'A' Stuck On' is the direct counterpart to P0746. Manufacturer TSBs #PIP5974E and #PIE0720A list them together as they both point to the same underlying mechanical snap ring failure.
• P0700 — This is a generic code that simply means the Transmission Control Module (TCM) has stored a fault. It acts as a 'Check Engine Light' for the transmission, alerting you that a more specific code like P0746 is present.

Technical Service Bulletins (TSBs) & Recalls

• PIP5974E: Communicates that out-of-round 1-2-3-4-5-6 snap rings can cause code P0746 or P0747 and lists over a dozen parts to be replaced during the repair.
• PIE0720A: Ends a data-gathering period related to a 'no move' condition in Drive, Neutral, or Reverse associated with codes P0746 and P0747.
• PIE0720: Initiated a data-gathering effort for a 'no move' condition linked to codes P0746 and P0747.

Platform-Specific Known Issues

• A known issue, documented in GM Preliminary Information Bulletin #PIP5974E, involves the 1-2-3-4-5-6 clutch snap rings being out of round. This mechanical failure is a direct cause of DTC P0746 or P0747.
• TSB PIP5974E explicitly warns technicians: "Do not replace the Control valve body assembly (Valve body) or Control valve solenoid body assembly (Solenoid body) as these are not related to the concern."
• GM Technical Bulletins #PIE0720A and #PIE0720 address a severe symptom associated with codes P0746 and P0747: the vehicle may not move when placed in Drive, Neutral, or Reverse, confirming a serious internal transmission problem.

Mechanic-Grade Diagnostic Values

• Transmission Line Pressure at Idle — expected: Greater than 345 kPa (50 psi). Failure: Pressure below 50 psi indicates a potential major internal hydraulic leak, pump failure, or valve body issue, consistent with the known snap ring failure.
• Transmission Fluid Temperature (TFT) for Level Check — expected: 85–95°C (185–203°F). Failure: Checking the fluid level outside of this temperature range will result in an inaccurate (under-filled or over-filled) reading.
• Pressure Control Solenoid (PWM type) Coil Resistance — expected: 5 to 30 Ohms. Failure: A reading of infinite resistance (open circuit) or near zero ohms (short circuit) indicates a failed solenoid coil.

Scan Tool Commands That Help

• GDS2 (or equivalent professional scan tool): Transmission Adaptation Reset / Clear Transmission Adapts — This function must be performed after replacing a transmission, valve body, or solenoids. It clears the learned values for clutch engagement, forcing the TCM to relearn the hydraulic characteristics of the new components.
• GDS2 / Tech 2 (with test plate): Solenoid Activation / Output Control — During advanced diagnostics (typically with the valve body on a bench), a technician can use a scan tool to command individual solenoids on and off while applying air pressure to test mechanical function and check for leaks. This definitively confirms if a solenoid is mechanically stuck or electrically non-responsive.

Wiring & Ground Locations

• F39 (Instrument Panel Fuse Block) — Located on the left side of the dashboard, accessible when the driver's door is open.. This fuse is designated for the 'Transmission control module 1/Battery 1' on 2021 models, making it a primary power source for the TCM that controls the solenoids.
• G401 — On the right side of the rear compartment, under the trim panel, to the rear of the right wheel well.. A GM bulletin identified loose or missing connections at this ground point as a cause for numerous communication (U-series) DTCs. Poor grounding can cause erratic module behavior, potentially affecting TCM operation and leading to incorrect fault codes.
• Transmission Case Connector (Pin 1) — The main electrical harness connector on the transmission case.. On the related 9T50 transmission, the control wire for the 1-2-3-4-5-6 clutch solenoid is a Blue wire at Pin 1. Since P0746 relates to the solenoid controlling this same clutch, this pin is a critical point for testing voltage and resistance between the TCM and the solenoid.

Real Owner Repair Stories

• Gears Magazine, 'Listen for the Snap' (General 2023/2024 GM vehicles with 9T45/60/65 transmissions (same family as Acadia)) — Slippage and a P0746 DTC.
  ❌ Tried (didn't work) The article warns against assuming it's a simple solenoid or valve body issue, which is the common misdiagnosis.
  ✅ What actually fixed it The root cause was identified as a manufacturing defect in the snap ring that retains the 1-2-3-4-5-6 clutch plates, causing it to pop out of its groove. The fix required transmission disassembly to inspect and replace the clutch components, confirming the guidance in TSB PIP5974.

Model Year Variations Within This Range

• 2023-2024: Transmissions with a Julian build date between 23 274 (October 1, 2023) and 24 113 (April 22, 2024) are identified in TSB PIP5974E as having a high risk of the 1-2-3-4-5-6 clutch snap ring failure that directly causes code P0746.