P2797 on 2017-2019 Chrysler Pacifica Hybrid: Auxiliary Pump Causes and Fixes

What's Unique About the 2017-2019 Chrysler PACIFICA PLUG-IN HYBRID

This code is specific to the Pacifica Hybrid model due to its e-Flite Si-EVT transmission, 🎬 See a deep dive into how this hybrid transaxle works. which relies on the electric auxiliary pump for operation in EV mode. Unlike conventional transmissions, this pump's function is essential for basic vehicle movement when the gas engine isn't running. Chrysler has issued multiple software updates to address incorrect fault logic that can trigger this code, making a software check a unique and critical first step for this vehicle.

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 is on
• "Service Transmission" or "Service Hybrid System" message on the dash
• "Propulsion Power Reduced" message
• Vehicle may not enter or stay in electric-only (EV) mode
• Delayed, harsh, or missed gear shifts.
🎬 Watch: A breakdown of common transmission symptoms and fixes.
• Vehicle may not move from a stop.
• Inability to pass a state emissions test due to a permanent fault code.

Most Likely Causes

1. Outdated Control Module Software 🔴 High Probability Multiple TSBs (#08-114-22, #08-107-26, #08-079-26, #08-010-21) have been issued by Chrysler for a range of DTCs, including P2797, that are resolved by flashing the control modules with updated software.
   How to confirm: A Chrysler dealership or a qualified shop with access to OEM software (wiTECH) can check if the vehicle's control modules have the latest updates by checking the VIN against TSBs.
   Typical fix: Flashing/reprogramming the Hybrid Control Processor (HCP) and/or Power Inverter Module (PIM) to the latest software version.
   Est. part cost: $0
2. Failed Auxiliary Transmission Fluid Pump 🟡 Medium Probability → Shop Transmission Assembly The electric pump runs frequently in hybrid operation, leading to eventual wear. Internal motor or mechanical faults can develop over time.
   How to confirm: After confirming software is up-to-date, a technician can use a scan tool to command the pump on and monitor its performance. If it fails to activate or meet pressure/speed specifications, it is likely faulty.
   Typical fix: Replacement of the auxiliary transmission fluid pump assembly.
   Est. part cost: $215-$320
3. Damaged Wiring Harness or Connectors ⚪ Low Probability Wiring to the transmission can be susceptible to chafing or corrosion. There was also a recall for internal transmission wiring shorts on 2017-2023 models, which could be related.
   How to confirm: Visually inspect the wiring harness leading to the auxiliary pump for signs of damage. This may require removing the front left wheel and wheelhouse liner. Test for power and ground at the pump connector.
   Typical fix: Repairing the damaged section of wire and securing the harness. In severe cases, the harness may need replacement.
   Est. part cost: $20-$300

Rare But Worth Checking

• Failed Power Inverter Module (PIM): The PIM (also called the Drive Motor Generator Power Inverter Control Module) is the module that controls the pump. While uncommon, an internal failure of the module's driver circuit can cause this code. This is typically a diagnosis of exclusion after the pump and wiring have been verified as good.

Diagnosis Steps

1. Scan the vehicle for all Diagnostic Trouble Codes (DTCs). Note any other codes that appear with P2797.
2. Using the vehicle's VIN, check with a Chrysler dealer or use a professional service to see if TSBs #08-114-22, #08-107-26, #08-079-26, or #08-010-21 apply. If so, have the relevant control modules updated first.
3. If software is up to date, perform a thorough visual inspection of the wiring harness and electrical connector for the auxiliary transmission fluid pump. Access may require removing the front left wheel and wheelhouse liner.
4. Using a capable scan tool (like wiTECH), command the auxiliary pump to activate. Monitor its reported speed and pressure to see if it matches the command.
5. If the pump does not activate, check the 15 Amp fuse in location F10 of the under-hood fuse box.
6. If the fuse is good, test for power and ground at the pump's electrical connector with the key on.
7. If power and ground are present but the pump does not run, the auxiliary transmission fluid pump has likely failed and requires replacement.
8. If power or ground is missing, trace the circuit back to the Power Inverter Module (PIM) to identify the break in the circuit.

Parts You'll Likely Need

• Auxiliary Transmission Fluid Pump Kit (OEM #68729718AB) — If software and wiring are good, the pump itself is the component that fails, requiring replacement.
  Trusted brands: Mopar
  OEM price range: $215-$320
  Aftermarket price range: N/A

Related Codes That Often Appear With This One

• P06E4 — Listed together in TSBs #08-107-26, #08-079-26, and #08-010-21 as codes that can be resolved with a software update.
• P07B5 — Listed together in TSBs #08-107-26, #08-079-26, and #08-010-21 as codes that can be resolved with a software update.
• P177C — Listed together in TSBs #08-107-26, #08-079-26, and #08-010-21 as codes that can be resolved with a software update.
• P0A46 — Listed together in TSB #08-114-22 as a code that can be resolved with a software update.

Technical Service Bulletins (TSBs) & Recalls

• 08-114-22: Addresses P2797 and other codes on 2019 models, likely fixed with a software update.
• 08-107-26: Lists P2797 on 2018 models as a code that can be addressed by a software update.
• 08-079-26: Lists P2797 on 2017 models as a code that can be addressed by a software update.
• 08-010-21: Mentions P2797 on 2018 models as one of several DTCs that may be set, often pointing to a software fix.

Platform-Specific Known Issues

• A recall was issued for 2017-2023 Pacifica Hybrids for an internal transmission wiring connector that could short circuit, causing an unexpected engine shutdown. 🎬 Watch: Why your Pacifica Hybrid might suddenly lose power. While not directly citing P2797, it highlights the known wiring issues within this transmission. The fix involves a software update to the Power Inverter Module (PIM).

Mechanic-Grade Diagnostic Values

• Auxiliary Transmission Fluid Pump Speed vs. Commanded Speed — expected: Actual speed should closely match the speed commanded by the scan tool.. Failure: The code may be triggered if the actual pump speed differs from the commanded speed by more than 500 RPM for several seconds.

Hidden / Shadow Codes Worth Checking

• P2797 as a Permanent DTC (PDTC): A Permanent DTC is stored in a non-volatile memory and cannot be cleared by a standard 'erase codes' function or by disconnecting the battery. The vehicle's computer must run and pass its internal self-test for the auxiliary pump circuit, which often requires a specific drive cycle, before it will clear the code. This can cause a vehicle to fail an emissions test even after the repair is complete if the drive cycle has not been run. (see via A scan tool that supports reading Permanent DTCs. Many modern professional and consumer-grade scanners have this capability.)

Scan Tool Commands That Help

• wiTECH (Chrysler OEM Software): Auxiliary Transmission Fluid Pump activation / speed command — This is a critical bidirectional test to use after verifying software is up-to-date. It allows a technician to manually command the pump to turn on (e.g., to 50% speed) and monitor its live data response (actual speed, pressure). This directly tests the pump's mechanical function and its circuit, isolating it from the vehicle's automated commands.

Wiring & Ground Locations

• Fuse F10 (Hybrid) — In the under-hood Power Distribution Center, located in the engine compartment near the battery.. This 15 Amp fuse is labeled for the 'High Temp Aux Pump & HV Electric Coolant Htr Enable' on 2018-2019 Hybrid models. It is a primary power source for the pump's control circuit and should be one of the first electrical checks if the pump is inoperative.

Real Owner Repair Stories

• Reddit user on r/MechanicAdvice (2018 Chrysler Pacifica Hybrid) — Check engine light was on, vehicle would not charge, and it failed an emissions test due to a permanent code.
  ❌ Tried (didn't work) Replacing the 12V engine battery, which tested low but did not resolve the check engine light.
  ✅ What actually fixed it A dealership visit confirmed the issue was software-related. The fix was applying the software updates specified in the Technical Service Bulletins that address P2797 and other related codes (P06E4, P07B5).

OEM Part Supersession History

• 68729718AA → 68729718AB — Part revision or update by the manufacturer. Reasons are not typically disclosed but usually involve improvements to durability or design.