P2797 on 2021-2023 Chevrolet Bolt EV: Auxiliary Transmission Pump Failure Causes and Fixes

What's Unique About the 2021-2023 Chevrolet BOLT EV

The Chevrolet Bolt EV and EUV platform is unique because this code is directly linked to a known manufacturing issue. General Motors issued Technical Service Bulletin (TSB) #21-NA-148, which identifies that the auxiliary transmission fluid pump can fail due to an out-of-spec soldering process during its assembly. Unlike in some other vehicles where this code might be caused by wiring or software, on the Bolt, the pump itself is the most common point of failure. This issue can appear on very low-mileage vehicles, with many owner reports of failures under 1,000 miles, and some within the first 100 miles of ownership.

Diagnostic Flowchart

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

Generation note: This issue affects both the refreshed first-generation Bolt EV (2021-2023) and the first-generation Bolt EUV (2022-2023), as they share the same drive unit and auxiliary pump design. TSB #21-NA-148 explicitly covers both models.

Symptoms You May Notice

• "Propulsion Power is Reduced" message on the Driver Information Center (DIC).
• Illuminated Malfunction Indicator Lamp (Check Engine Light) or Service Vehicle Soon light.
• Vehicle speed may be limited, sometimes to around 30 mph.
• OnStar diagnostic report will identify an issue with the Auxiliary Transmission Pump System.

Most Likely Causes

1. Failed Auxiliary Transmission Fluid Pump 🔴 High Probability → Shop Transmission Assembly A known manufacturing defect involving an out-of-spec soldering process is the primary cause, as identified in GM TSB #21-NA-148. GM refers to this as a 'part quality spill'. This leads to an internal failure of the pump motor. Failures are common on very new vehicles, with numerous reports of the issue occurring under 1,000 miles.
   How to confirm: A technician will confirm the code with a scan tool. The diagnosis is straightforward based on TSB #21-NA-148, which directs the technician to replace the pump if DTC P2797, P2798, or P0C2D is present. A technician can also use a GDS2 scan tool to manually command the pump on and monitor its speed; a deviation of more than 500 RPM from the commanded speed indicates failure.
   Typical fix: Replace the transmission fluid pump assembly. The pump motor is not internally serviceable. This repair is covered under GM's 5-year/60,000-mile powertrain warranty.
   Est. part cost: $115-$340

Rare But Worth Checking

• Damaged Wiring Harness: While the pump is the most common failure point on the 2021-2023 models, an older TSB for the 2017 Bolt (17-NA-030) noted that damaged wire insulation or corrosion on the pump's wiring harness could also cause this code. It's a much less likely cause on newer models but remains a theoretical possibility.
• Software Glitch in Cold Weather: Some owners have reported experiencing the 'Propulsion Power is Reduced' message and code P2797 only in freezing temperatures after a remote start. The hypothesis is that remote start only preconditions the cabin and not the drive unit, and the cold, viscous fluid causes the pump to report a performance issue. Some users report that power cycling the car or performing several hard accelerations/regenerations can clear the code temporarily. However, if the code persists, it indicates the more common pump hardware failure.

Diagnosis Steps

1. Verify the presence of DTC P2797, P2798, or P0C2D with a professional OBD-II scan tool.
2. Note the primary symptom, which is typically the 'Propulsion Power is Reduced' message on the DIC.
3. Consult GM Technical Service Bulletin #21-NA-148, which identifies a known manufacturing defect with the pump due to a 'part quality spill' from a bad soldering process.
4. Using a GM GDS2 scan tool, a technician can use the 'Auxiliary Fluid Pump Control' bidirectional command to manually activate the pump and monitor its actual speed versus the commanded speed. A deviation greater than 500 RPM indicates failure.
5. Visually inspect the wiring harness leading to the auxiliary transmission fluid pump for any obvious signs of damage or corrosion. Access to the connector may require removing the left front wheelhouse liner.
6. Following the guidance in TSB #21-NA-148, the primary diagnostic step is to confirm the code and proceed with replacing the faulty pump. The TSB explicitly states the pump is not serviceable.

Parts You'll Likely Need

• Automatic Transmission Fluid Pump (OEM #25204070) — This is the component identified by GM as having a manufacturing defect (bad solder joint) that causes code P2797. TSB #21-NA-148 was updated in March 2024 to specify this new part number, replacing the previous one (25200558). Some parts sites and recent owner repairs show 25207705 as a newer replacement for 25204070.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $115-$340
  Aftermarket price range: N/A

Related Codes That Often Appear With This One

• P2798 — This code for 'Auxiliary Transmission Fluid Pump Circuit High' is often triggered along with P2797, as both relate to the electrical performance of the same pump. TSB #21-NA-148 lists both codes as part of the same issue.
• P0C2D — This code for 'Drive Motor 'A' Inverter Power Supply Circuit Low Voltage' can also appear with P2797. It is also mentioned in TSB #21-NA-148 as being related to the same pump performance issue.
• P0AC4 — Some owners have reported seeing P0AC4 (Hybrid/EV Powertrain Control Module Requested MIL Illumination) in conjunction with P2797, as it is a generic code indicating that a module has requested the check engine light.

Technical Service Bulletins (TSBs) & Recalls

• 21-NA-148: Diagnostic Aid – DTC P2797, P2798 or P0C2D for Transmission Fluid Pump Performance. This is the primary bulletin identifying the faulty pump as the cause. It was revised in March 2024 to update the replacement part number.
• 17-NA-030: Malfunction Indicator Lamp (MIL) Illuminated - DTCs P2797 and/or P2798 Set. An older TSB for 2017 models pointing to potential wiring harness issues, which is a less likely cause on 2021-2023 models.

Platform-Specific Known Issues

• GM TSB #21-NA-148 directly addresses DTC P2797 on the 2021-2023 Bolt EV and 2022-2023 Bolt EUV. It states a 'part quality spill' due to an out-of-spec soldering process is the cause and the corrective action is to replace the pump.
• Extremely Low Mileage Failures: A significant number of owners report this failure occurring on brand new vehicles, some with fewer than 200 miles. This points directly to a manufacturing defect rather than wear and tear.
• Owner Repair Experiences: Owners on forums like Reddit's r/BoltEV report that the dealer repair is straightforward once the part is available. The process involves confirming the code, ordering the pump, and replacing it. Repair times at the dealership can range from a few days to several weeks, primarily depending on part availability.

Mechanic-Grade Diagnostic Values

• Auxiliary Pump Speed Deviation — expected: Less than 500 RPM difference between commanded and actual speed.. Failure: A difference greater than 500 RPM for more than 4 seconds will set DTC P2797.
• Auxiliary Pump Line Pressure (Engine Off, Pump Commanded ON) — expected: 145 kPa (21 psi) or greater.. Failure: Pressure below this value indicates a failed pump or an internal leak.
• Ignition Voltage at Auxiliary Pump Control Module — expected: 8-18 Volts.. Failure: Voltage outside this range points to a power supply or ground issue that needs to be resolved before condemning the pump.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Auxiliary Fluid Pump Control — During diagnosis, a technician uses this command to manually turn the auxiliary pump ON (e.g., to 50% speed) to verify if it runs and to monitor its actual speed versus the commanded speed without driving the vehicle.

Wiring & Ground Locations

• Auxiliary Transmission Fluid Pump Connector — The pump is attached to the driver's side of the transmission. The electrical connector and harness are accessible by removing the front left wheelhouse liner.. In the rare event that the pump itself is not faulty, this is the primary location to inspect for wiring damage, corrosion, or a poor connection, as noted in older TSBs for the Bolt.

Real Owner Repair Stories

• Reddit user maddumpies (2023 Bolt with 32,000 miles) — Displayed 'reduced propulsion power' error, speed limited to ~30 mph. Error message disappeared but check engine light remained on. OnStar confirmed the code.
  ✅ What actually fixed it The dealer confirmed the pump had failed and replaced it under warranty. The entire process, including waiting for the part to be shipped to the dealer, took one week.
• Reddit user convincedbutskeptic (2023 Bolt EV with 1,600 miles) — 'Propulsion power reduced' error appeared after parking the vehicle.
  ✅ What actually fixed it The dealer diagnosed a failed transmission fluid pump. The part was on backorder and the repair took 17 days to complete. The replacement part number noted on the repair order was 25207705. The repair was covered under warranty and a loaner vehicle was provided.
• Reddit user bobfatherx (2023 Bolt EUV with 170 miles) — DTC P2797 occurred 4 days after delivery. The 30 mph speed limit could be temporarily cleared by turning the car off and on.
  ✅ What actually fixed it The vehicle was taken for service and the transmission fluid pump was replaced under warranty. The repair took approximately 18 days, presumably due to part availability.
• Reddit user IAmRootAMA (2023 Bolt EUV with 750 miles) — The 'P2797 Auxiliary Transmission Fluid Pump' error appeared after about two weeks of ownership.
  ✅ What actually fixed it This is an unresolved case with an important lesson: The warning light went away on its own before the service appointment. The service manager told the owner they could not perform a warranty repair without an active issue/code. The owner was told to call back if/when the light returned.

OEM Part Supersession History

• 25200558 → 25204070 — Part number updated in official GM service documentation.
  Heads up: TSB 21-NA-148 was revised in March 2024 to specify 25204070 as the replacement part, superseding the older 25200558.
• 25204070 → 25207705 — Newer part number used in recent dealership warranty repairs.
  Heads up: Owner repair stories from mid-2024 show 25207705 being installed by dealers to fix the P2797 code, indicating it is the latest service replacement part.