P2797 on 2020-2025 Buick Encore GX: Auxiliary Transmission Pump Failure Guide

What's Unique About the 2020-2025 Buick ENCORE GX

The Buick Encore GX, along with its platform-mate the Chevrolet Trailblazer, has a known issue with the auxiliary transmission fluid pump used in the 9T45 (RPO MRG) transmission. General Motors has acknowledged this by issuing Technical Service Bulletin (TSB) 19-NA-200, which specifically addresses DTC P2797 on these vehicles. The problem is so common that the TSB outlines a direct repair: replacing both the auxiliary pump and its wiring harness due to a high rate of internal pump failures.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on.
• Auto Start/Stop system is inoperative.
• A message on the driver information center indicating the start/stop system is disabled.
• Hesitation, jerk, or bump when accelerating from a complete stop.
• Reduced acceleration or feeling of power loss.
• In rare, severe cases, the vehicle may not move.

Most Likely Causes

1. Internal Failure of the Auxiliary Transmission Fluid Pump 🔴 High Probability → Shop Transmission Assembly This is a well-documented issue for this platform, as confirmed by GM's Technical Service Bulletin 19-NA-200, which points directly to internal pump failure as the primary cause. The bulletin has been updated multiple times to expand the model years affected, indicating the persistence of the problem.
   How to confirm: A professional technician will use a scan tool to confirm DTC P2797 is present and command the auxiliary pump to activate. If the pump does not respond or its performance metrics (like pressure or RPM) are out of spec, the pump is faulty. The TSB is the primary diagnostic path. Specifically, with the pump commanded on, the transmission line pressure should be at least 145 kPa (21 psi); if not, the pump has likely failed.
   Typical fix: Replace the auxiliary transmission fluid pump and the associated wiring harness as a set, per TSB 19-NA-200.
   Est. part cost: $250-$450
2. Damaged or Faulty Wiring Harness/Connector 🟡 Medium Probability The wiring harness is a known failure point. TSB 19-NA-200 was officially updated on February 18, 2021, to mandate the replacement of the wiring harness along with the pump, suggesting that replacing the pump alone is not a complete or durable repair. Early versions of the TSB only advised inspecting the harness for backed-out terminals.
   How to confirm: Visually inspect the wiring harness and connectors leading to the auxiliary pump for any signs of corrosion, backed-out pins, or damage. A resistance check between the harness connector (X175) and the pump should show less than 2 ohms. However, given the TSB, replacement is recommended regardless of visual condition when the pump is replaced.
   Typical fix: Replace the auxiliary transmission pump wiring harness. GM's official procedure mandates replacing this harness whenever the pump is replaced for this issue.
   Est. part cost: $50-$100
3. Failed Auxiliary Pump Control Module ⚪ Low Probability
   How to confirm: This is typically diagnosed by exclusion. If the pump and wiring have been replaced according to the TSB and the issue persists, the control module may be at fault. The pump itself does not typically require programming, but the control module might.
   Typical fix: Replace the control module. This may require programming to the vehicle's VIN.
   Est. part cost: $200-$400

Diagnosis Steps

1. Verify the code with a professional OBD-II scan tool.
2. Confirm the primary symptoms: Check Engine Light is on and the Auto Start/Stop feature is disabled.
3. Reference TSB 19-NA-200, which directly addresses this code for the Encore GX and its platform mates.
4. Using a scan tool like GDS2, use the 'Auxiliary Fluid Pump Control' function to command the pump ON.
5. While commanded ON, monitor the 'Commanded Pump Speed' and 'Actual Pump Speed' PIDs. A difference greater than 500 RPM for more than 4 seconds indicates a fault.
6. With the engine off and pump commanded ON, check the transmission line pressure. It should be 145 kPa (21 psi) or greater. If pressure is low or zero, the pump has likely failed.
7. If the pump does not run, inspect the wiring harness (Connector X175) and check for resistance. A reading of 2 ohms or more indicates a problem in the circuit.
8. Per TSB 19-NA-200, the primary fix is to replace both the auxiliary transmission fluid pump and the wiring harness.
9. Clear the trouble codes and perform a test drive to verify the repair and ensure the start/stop system functions correctly.

Parts You'll Likely Need

• Auxiliary Transmission Fluid Pump (OEM #24297279) — This is the component that fails internally, causing the P2797 code, as identified by GM's service bulletin. This part number supersedes previous versions 24291073, 24291074, 24297280, and 24299204.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $250-$400
  Aftermarket price range: $180-$300
• Auxiliary Transmission Wiring Harness (OEM #24298763) — The official repair procedure from GM mandates replacing this harness along with the pump to ensure a lasting repair, per TSB 19-NA-200.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $50-$100
  Aftermarket price range: $40-$80

Related Codes That Often Appear With This One

• P2796 — This code indicates an open circuit for the auxiliary pump, which can be caused by the same internal pump or wiring harness failure that triggers P2797.
• P27EC — On some newer GM models like the 2025 Chevrolet Equinox, TSB 19-NA-200 notes that DTC P27EC (transmission range control valve position sensor circuit performance) may set *before* P2797 when there is an auxiliary pump or harness failure.

Technical Service Bulletins (TSBs) & Recalls

• 19-NA-200: Start/Stop Inoperative, Malfunction Indicator Lamp (MIL) Illuminated – DTC P2797 Set. This bulletin confirms the cause is often an internal failure of the auxiliary fluid pump and instructs technicians to replace both the pump and its wiring harness. It has been revised multiple times, with a key update in Feb 2021 adding the harness to the procedure and later updates expanding the affected model years to 2025.

Platform-Specific Known Issues

• A widespread and documented issue with internal failure of the auxiliary transmission fluid pump, leading GM to issue TSB 19-NA-200.
• This issue is shared with platform mates like the Chevrolet Trailblazer and other GM vehicles using the 9TXX series transmissions.

Mechanic-Grade Diagnostic Values

• Auxiliary Pump Line Pressure — expected: 145 kPa (21 psi) or greater. Failure: Pressure below 145 kPa when the pump is commanded ON with the engine off.
• Auxiliary Pump Speed Differential — expected: Less than 500 RPM difference between commanded and actual speed.. Failure: A difference greater than 500 RPM for more than 4 seconds.
• Auxiliary Pump Harness Resistance — expected: Less than 2 ohms. Failure: Resistance of 2 ohms or greater between the harness connector (X175) and the pump.

Hidden / Shadow Codes Worth Checking

• P27EC: Transmission Range Control Valve Position Sensor Circuit Performance. On 2025 model year vehicles like the Chevrolet Equinox, this DTC will set *before* P2797 in the event of an auxiliary pump or harness failure. (see via Standard OBD-II scan tool. This is not a sub-code but a precursor code on specific model years, as noted in TSB 19-NA-200.)

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Auxiliary Fluid Pump Control — During diagnosis to manually command the auxiliary pump ON, typically to 50% speed. This allows a technician to verify if the pump motor is functional, listen for noise, and check if it can build the required line pressure without the engine running.

Wiring & Ground Locations

• X175 — This is the electrical connector for the VT40 Transmission Auxiliary Pump Harness.. This is the connector where a technician would test for resistance to determine if the wiring harness is faulty before replacing parts.

"I Checked Everything" — The Actual Cause

• The history of TSB 19-NA-200 demonstrates a pattern where the initial, standard fix was insufficient. Initially, the procedure was to replace only the auxiliary pump. However, many vehicles likely had the P2797 code return because the wiring harness was also faulty or prone to failure. This led GM to update the bulletin on February 18, 2021, to mandate the replacement of the wiring harness (PN 24298763) alongside the pump, which has since become the standard, durable repair.

OEM Part Supersession History

• 24291073, 24291074, 24297280, 24299204 → 24297279 — Part has been updated by the manufacturer to improve reliability and address the internal failure mode causing P2797.

Model Year Variations Within This Range

• Pre-Feb 2021: The official TSB (19-NA-200) only mandated replacing the auxiliary pump; harness replacement was not required, only inspection.
• Post-Feb 2021: TSB 19-NA-200 was revised to mandate the replacement of both the auxiliary pump and the wiring harness (24298763) to ensure a complete repair.
• 2024-2025: The model years covered by TSB 19-NA-200 were expanded in March 2025 to include up to the 2025 model year.