P2797 Electric auxiliary transmission fluid pump not performing

Auxiliary transmission fluid pump performance / stuck off

P2797 in short

P2797 means the auxiliary transmission fluid pump, used on hybrids and stop-start cars to keep pressure while the engine is off, did not deliver the pressure asked of it. Wiring or a failed pump are the usual suspects. Get it checked soon, and have it towed if the car stops moving.

Some vehicles use a small electric pump to keep the transmission's hydraulic pressure up while the engine is stopped for auto-stop. The computer commands the pump and checks that it responds. If the pump cannot make the requested pressure, it sets P2797.

Sources describe a damaged pump harness, a pump that has failed, a pump relay or driver module fault, and in some cases a weak 12-volt battery. Water getting into the pump is named as a common failure on one reference.

Fixes differ a lot by maker. GM has bulletins that replace the pump or repair a chafed harness, Subaru has new transmission computer software, and Ford has software for secondary modules on some F-150s. Do not replace the pump before checking the wiring and bulletins.

Most likely causes

  1. Damaged or chafed wiring to the auxiliary pump

    Supported by vehicle data
    Why it ranks here
    GM's bulletin for 2009-2010 hybrid trucks and SUVs names a cut or chafed auxiliary pump harness as causing the auto stop to misbehave with P2797 set, and a later GM bulletin says to inspect the wiring before replacing the pump.
    What would change this
    Rises if the harness shows chafing or a break, or the pump runs when powered directly. Falls if wiring and connectors test clean.

  2. Auxiliary transmission pump worn out or failed

    Supported by vehicle data
    Why it ranks here
    GM bulletins for 2019-2025 Malibu, Equinox, Trailblazer and Encore GX replace the transmission auxiliary pump when P2797 sets with start/stop inoperative. Sources also name pump bearing failure.
    What would change this
    Rises if the pump does not run or draw current when commanded. Falls if the harness or software is at fault.

  3. Control module software that needs an update

    Supported by vehicle data
    Why it ranks here
    Subaru has new transmission computer files for P2797 on 2023-2024 Legacy and Outback, and Ford has a software bulletin for P2797 on some 2022-2025 F-150 models.
    What would change this
    Rises if a dealer finds your VIN covered and the software out of date. Falls if it is already current.
    How to test the transmission control module (tcm)

  4. Weak 12-volt battery, pump relay or corroded connector

    Possible — needs testing
    Why it ranks here
    Reference pages list a discharged battery, a failed pump relay and corroded wiring as causes, but no bulletin ties them to a specific vehicle.
    What would change this
    Rises if the battery tests weak or a relay or fuse is faulty. Falls if power and ground at the pump test normal.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored codes from every module and note any other pump, hybrid or battery codes stored with P2797.

    Low riskTool: scan tool that reads all modules

    • IfOther pump or hybrid-control codes are stored too (for example P0C2B, P2798 or P0AC4)

      It meansFollow the maker's diagnosis for that combination first, since GM bulletins treat them together.

      Go to step 2

    • IfP2797 is the only code

      It meansCheck for a bulletin for your vehicle.

      Go to step 2

  2. Ask a dealer whether your VIN has a pump replacement or software update for P2797.

    Low risk

  3. Have a shop inspect the pump harness and connector, check fuse, relay, battery and ground, then command the pump on with a bidirectional scan tool.

    Best left to a shopTool: bidirectional scan tool, multimeter

    Warning:Transmission and high-voltage hybrid components are involved. Leave testing to a shop.

Symptoms

  • Rough or missing engine auto-stop, or start/stop turned off
  • Hesitation or a bump when pulling away
  • Check engine light or a reduced-power message on hybrids and EVs
  • Transmission slips, overheats or the vehicle will not move Gets more serious: stop and have it checked.

How to fix

  1. Ask a dealer whether your VIN has an open software update or pump bulletin for P2797.

Parts and cost context

  • Transmission control module (TCM):Some makers fix P2797 with software, so a module is not the first part to replace. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 2019–2025 · Malibu

    Supported by vehicle data

    GM bulletin 19-NA-200 replaces the transmission auxiliary pump for start/stop inoperative with P2797 on the Malibu, Equinox and Trailblazer. Whether the bulletin is still current is not verified.

  • 2009–2013 · Silverado 1500

    Supported by vehicle data

    GM bulletins PI-0209 and PIP4873A cover P2797 on the hybrid Silverado: a chafed pump harness is named, and the later one says not to replace the pump before diagnosis. Whether the bulletin is still current is not verified.

  • PI-0209Status unverified

    Rough or no auto stop, MIL on, P2797

    2009–2010sierra, yukon · NHTSA 10036304

    Hybrid trucks and SUVs from GM brands. A cut or chafed auxiliary pump harness can make auto stop misbehave and set P2797.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • PIP4873AStatus unverified

    Diagnosis for P0C2B with or without P2797

    2008–2013silverado-1500, tahoe · NHTSA 10095613

    Says not to replace the auxiliary transmission fluid pump and to follow published diagnosis, starting with the wiring between the hybrid control module and the pump.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 19-NA-200Status unverified

    Start/stop inoperative, MIL on with P2797

    2019–2025malibu, equinox, trailblazer · NHTSA 10235801

    Repair procedure that replaces the transmission auxiliary pump.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 21-NA-148Status unverified

    Transmission fluid pump performance P2797, P2798 or P0C2D

    2021–2023bolt-euv, bolt-ev · NHTSA 10240188

    Diagnostic aid for a Propulsion Power is Reduced message with a service vehicle soon light.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Subaru

  • 2023–2024 · Legacy

    Supported by vehicle data

    Subaru bulletin 16-145-23R offers new transmission computer files for P2797 on the Legacy and Outback. Whether the bulletin is still current is not verified.

  • 16-145-23RStatus unverified

    TCM reprogramming for P2797

    2023–2024legacy, outback · NHTSA 11006941

    New transmission control module files to address cases of P2797.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2022–2025 · F-150

    Supported by vehicle data

    Ford TSB 26-2010 covers a wrench light with P2796/P2797 set in secondary diagnostic modules on some F-150s; the summary points to software. Whether the bulletin is still current is not verified.

  • TSB 26-2010Status unverified

    Wrench light with P2796 and/or P2797

    2022–2025f-150 · NHTSA 11027797

    Some F-150 models may show the powertrain wrench light with these codes stored in secondary diagnostic modules. The summary points to module software.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0700Transmission module requests the check engine light

    Same system Possible — needs testing

    P0700 is the general transmission-fault flag and may be stored along with P2797 when the transmission computer has logged a fault.

All Transmission codes

P2797 questions

Can I drive with P2797?

If the vehicle drives normally, you can usually get to a shop, but get it checked soon. Do not drive if it will not move, slips badly or overheats.

Should I replace the auxiliary pump right away?

No. GM tells technicians to check the wiring first on some trucks, and Subaru fixes some cases with software.

Sources and review

  1. OBD II error code P2797: Auxiliary Transmission Fluid Pump Performance — PartsAvatar
  2. P2797 Trouble Code: Auxiliary Transmission Fluid Pump Performance — TroubleCodes.net
  3. GM PI-0209: auto stop rough or inoperative, P2797 — General Motors (via NHTSA flat file)
  4. GM PIP4873A: P0C2B with or without P2797 — General Motors (via NHTSA flat file)
  5. GM 19-NA-200: start/stop inoperative with P2797 — General Motors (via NHTSA flat file)
  6. Subaru 16-145-23R: TCM reprogramming for P2797 — Subaru (via NHTSA flat file)
  7. Ford TSB 26-2010: wrench light with P2796/P2797 — Ford (via NHTSA flat file)
  8. GM 21-NA-148: transmission fluid pump performance P2797/P2798/P0C2D — General Motors (via NHTSA flat file)
Last reviewed
Written by
Saurabh K.
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