P2797 on 2016-2019 Chevrolet Volt: Auxiliary Transmission Pump Failure Causes and Fixes

What's Unique About the 2016-2019 Chevrolet Volt

The Gen 2 Volt's 5ET50 transaxle relies heavily on its electric drive unit, making the auxiliary transmission pump's function non-negotiable for basic operation, unlike in a conventional car where it might only support an auto start/stop feature. While the pump itself can fail, a known issue on the architecturally similar Bolt EV is a wiring harness that can chafe and short out, as detailed in TSB 17-NA-030. This makes a thorough wiring inspection a critical first step for any Volt owner with this code, potentially saving them from a costly and unnecessary pump replacement. Manufacturer documentation in Bulletin #PIC6294 further guides dealers on diagnosing the vehicle when it specifically sets codes P0AC4 and P2797 together.

Symptoms You May Notice

• "Propulsion Power is Reduced" message on the driver information center
• Check Engine Light is on
• Vehicle may not start or may stall
• Noticeable hesitation or jerking during acceleration or when launching from a stop
• Delayed or harsh transmission shifting
• "Shift to Park" message may appear simultaneously

Most Likely Causes

1. Damaged Auxiliary Transmission Pump Wiring Harness 🔴 High Probability → Shop Transmission Assembly The wiring harness for the pump can be susceptible to chafing, causing the signal wire to short to ground or develop corrosion. This issue is documented in GM TSB 17-NA-030 for the architecturally similar Bolt EV, which instructs technicians to inspect the harness for cuts or corrosion before replacing any parts. This is a common failure pattern on many GM vehicles with auxiliary pumps.
   How to confirm: Visually inspect the wiring harness leading to the auxiliary transmission pump, which is located on the driver's side of the transmission. This requires removing the front left wheel and wheelhouse liner. Look for any signs of rubbed-through insulation, corrosion, or contact with other components. The TSB specifically points to inspecting for open cuts or corrosion in the insulator.
   Typical fix: Repair the damaged section of the wire and protect the harness with high-quality woven polyester electrical tape or loom to prevent future damage. This repair requires no new parts if caught early.
   Est. part cost: $0-$20
2. Internal Failure of the Auxiliary Transmission Fluid Pump 🟡 Medium Probability → Shop Transmission Assembly The electric motor within the pump assembly can burn out or the pump mechanism can seize. This is a documented failure part on several other GM vehicles from the same era that use a similar design, as noted in TSB 19-NA-200 for the Malibu and other models. Reddit users on r/BoltEV and r/volt have reported this failure requiring pump replacement.
   How to confirm: If the wiring harness is confirmed to be in good condition with proper voltage and ground, a diagnostic scan tool (like the dealer-level GDS2) can be used to command the pump on. If the pump does not run, its reported speed is erratic, or it fails to produce at least 21 psi (145 kPa) of line pressure, it has failed.
   Typical fix: Replace the auxiliary transmission fluid pump. This is a labor-intensive job as the pump is located inside the transmission housing on some related platforms, though it is externally mounted on the Volt.
   Est. part cost: $115-$400

Rare But Worth Checking

• Battery Energy Control Module (BECM) Failure: The 2016-2019 Volt is subject to a NHTSA investigation (PE23-018) for power loss issues related to BECM failure. While this may not directly set P2797, it can cause identical symptoms like 'Propulsion Power is Reduced' and stalling, making it a critical consideration during diagnosis. GM has extended warranty coverage for this component.
• Transmission Control Module (TCM) or Power Inverter Module Failure: → Shop Transmission Assembly It is possible, though uncommon, for the control module that commands the pump to fail. This should only be considered after the pump and its wiring have been proven to be good. On the Volt, the pump is controlled by a motor driver within the Drive Motor Generator Power Inverter Control Module.

Diagnosis Steps

1. Scan the vehicle for all Diagnostic Trouble Codes (DTCs). Note any other codes that are present with P2797, especially P2798.
2. Check for any applicable Technical Service Bulletins (TSBs) for your vehicle's VIN. Pay close attention to TSB 17-NA-030 (for the similar Bolt EV) regarding wiring inspection and TSB 18-NA-261 regarding BECM failure symptoms.
3. Raise and support the vehicle safely. Remove the front left wheel and wheelhouse liner to access the transmission area.
4. Locate the auxiliary transmission fluid pump and its electrical connector. Disconnect the connector.
5. Thoroughly inspect the wiring harness for any signs of chafing, melting, corrosion, or open circuits. Pay close attention to where the harness may rub against the chassis or other components.
6. If damage is found, repair the wire(s), then wrap the harness with protective tape (GM specifies Woven Polyester Electrical Tape) or loom. Reconnect, clear codes, and test drive to see if the fault returns.
7. If the wiring is intact, use a multimeter to check for proper power and ground at the pump connector with the vehicle on.
8. If power and ground are good and the wiring is intact, use a capable scan tool to command the auxiliary pump ON and monitor its performance. If it fails to run or meet pressure specifications (at least 21 psi), the pump itself is the most likely culprit and should be replaced.

Parts You'll Likely Need

• Auxiliary Transmission Fluid Pump (OEM #24297279) — This is the component that fails if the wiring harness is found to be in good condition. The part number 24297279 is listed for similar GM applications and is a likely fit. Another possible number is 23259627.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $115-$450
  Aftermarket price range: $100-$300
• Woven Polyester Electrical Tape / Wire Loom — Required to properly repair and protect a chafed wiring harness, which is a common cause of this code, as specified in GM TSBs.
  Trusted brands: Tesa, 3M
  OEM price range: $10-$20
  Aftermarket price range: $5-$15

Related Codes That Often Appear With This One

• P2798 — This code for 'Auxiliary Transmission Fluid Pump 'A' Speed/RPM' often appears alongside P2797, as both relate to the pump's operational performance. TSB 17-NA-030 for the Bolt EV lists both codes as resulting from the same wiring harness issue.
• P0AC4 — Stands for 'Hybrid Powertrain Control Module Requested MIL Illumination'. This is a generic code that often accompanies more specific faults like P2797 on hybrid vehicles, simply indicating that a fault has been detected in the hybrid system.

Technical Service Bulletins (TSBs) & Recalls

• 17-NA-030: Although for the Bolt EV, this TSB is highly relevant. It instructs technicians to inspect for a damaged wire insulation/short circuit in the transmission fluid pump harness as a cause for P2797 and P2798 before replacing the pump.
• 18-NA-261: Addresses no-start or MIL-on conditions related to internal BECM failure on 2016-2019 Volts, which can cause identical power loss symptoms and is a known issue under NHTSA investigation.
• 19-NA-206: Details the common 'Shift to Park' issue affecting 2016+ Volts, which can sometimes appear alongside other powertrain warnings like the one for P2797.
• Bulletin #19-NA-200: Provides a repair procedure for the MIL illuminated with DTC P2797 and notes that this can also cause the start/stop system to become inoperative.
• Bulletin #21-NA-148: Offers diagnostic aid for DTC P2797, P2798, or P0C2D regarding Transmission Fluid Pump Performance, specifically when a "Propulsion Power is Reduced" message is shown on the DIC.
• Bulletin #PIC6294: Communicates to dealers how to diagnose and repair the vehicle if it sets diagnostic trouble codes P0AC4 and P2797.

Platform-Specific Known Issues

• A NHTSA investigation (PE23-018) was opened for 2016-2019 Volts due to sudden power loss. This is often linked to a failing Battery Energy Control Module (BECM) and can present with the same 'Propulsion Power is Reduced' warning as code P2797.

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.
• Voltage at Pump Power Feed — expected: 12V ± 0.5V (with ignition ON). Failure: Low or no voltage indicates a problem with the power supply circuit, not necessarily the pump.
• Pump Control Module Ignition Voltage — expected: 8-18 Volts. Failure: Voltage outside this range points to a power supply or ground circuit issue that must be fixed before condemning the pump or module.
• Auxiliary Pump Harness to Pump Resistance — expected: Less than 2 ohms. Failure: Resistance of 2 ohms or greater indicates an open or high resistance in the circuit between the main harness connector and the pump itself.

Scan Tool Commands That Help

• GDS2 (GM Dealer Software): Auxiliary Fluid Pump Control / On/Off — This is the primary bidirectional test. It is used to manually command the pump ON to verify its mechanical operation (listening for noise) and to monitor the 'Actual Pump Speed' PID versus the 'Commanded Pump Speed' PID. This test quickly determines if the pump is responding to commands from the control module.

Wiring & Ground Locations

• Auxiliary Pump Harness Connector — Behind the front left wheel and wheelhouse liner, on the driver's side of the transmission assembly.. This is the primary access point for visually inspecting the harness for chafing—a common cause of P2797—and for performing voltage and resistance tests on the pump circuit.
• G107 (or similar G1xx ground) — Typically found on the left side of the engine block or bell housing area. GM's numbering scheme places G1xx grounds in the engine compartment.. A poor ground connection for the pump's control module can cause erratic operation and performance codes like P2797. Verifying this ground is clean and tight is a critical step if wiring tests show issues.
• T6 Power Inverter Module (PIM) Connector — On the Power Inverter Module, which is a large aluminum component of the hybrid powertrain.. On the related Gen 1 Volt, a known issue involves transmission fluid wicking up the wiring harness and contaminating this connector, causing various faults. While less documented on Gen 2, it's a potential point of failure to inspect if other diagnostics are inconclusive.

OEM Part Supersession History

• 24291073, 24291074, 24297280, 24299204 → 24297279 — Part consolidation and potential design revisions.
  Heads up: Ensure you are ordering the transmission fluid auxiliary pump (24297279) and not a similarly named coolant auxiliary pump (e.g., 23259627 or 23353644), as parts catalogs can be confusing.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Battery Energy Control Module (BECM) Failure 🔴 High — Common enough to trigger a NHTSA investigation (PE23-018) and a GM special coverage program. Can occur at various mileages. (Ref: TSB 18-NA-261)
• 'Shift to Park' Message 🟠 Medium — A very common issue across many GM models of this era, including the Volt. It prevents the vehicle from shutting off. (Ref: TSB 19-NA-206)
• Clogged EGR Cooler 🔴 High — Extremely common, especially on vehicles with over 60,000 miles. Causes P0401 and can lead to drivability issues. (Ref: TSB 18-NA-089)
• Shorted EGR Valve 🔴 High — Less common than the clogged cooler, but a failure can blow a shared fuse, disabling the engine coolant pump and causing sudden overheating.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used part is generally not recommended for the pump itself due to a documented history of failure on similar GM platforms. However, sourcing a used wiring harness pigtail from a salvage yard is a very sensible and cost-effective option if only the connector or a small section of wire is damaged.

Donor-vehicle mileage cap: roughly under 50000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a used pump: Ask for the donor vehicle's mileage and check if it was involved in a front-end collision that could have damaged the transmission.
• For a used harness/pigtail: Inspect the connector pins for any signs of corrosion, melting, or discoloration from overheating. Ensure the locking tabs are intact.
• Verify the part number on the component matches the required OEM number (24297279 for the pump).

OEM-only on this vehicle (don't cheap out):

• Auxiliary Transmission Fluid Pump

Brands owners have reported issues with on this vehicle:

• No specific brands are cited, but given the critical function and known OEM issues, unbranded or 'white-box' aftermarket pumps carry a high risk of premature failure.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P2798 — This is a companion code to P2797. TSB 17-NA-030, which addresses the chafed wiring harness, explicitly lists both P2797 and P2798 as codes caused by this specific failure.
• P0401 — This code for 'EGR Flow Insufficient' is unrelated to the transmission pump but is an extremely common reason for a Check Engine Light on the 2016-2019 Volt due to a frequently clogged EGR cooler. It can cause general drivability issues that may appear alongside other faults.

Frequently Asked Questions