P2797 on 2008-2013 GMC Yukon Hybrid: Auxiliary Pump Circuit Causes and Fixes

What's Unique About the 2008-2013 Gmc YUKON

This code is exclusive to GM vehicles with the 2-Mode Hybrid system (RPO HP2) and 2ML70 transmission (RPO M99), 🎬 Watch: A detailed teardown of the 2ML70 hybrid transmission including the Yukon, Tahoe, Escalade, and Silverado/Sierra Hybrids. Standard gasoline-only models lack this auxiliary electric pump. 🎬 See a technical overview of the GM 2-Mode Hybrid system The key issue for this platform, as documented by GM, is that wiring faults are a far more common cause than the pump itself. TSB PIP4873A explicitly states, "DO NOT REPLACE THE PUMP if dtc P0C2B is set current or history with or without other dtc's [like P2797]".

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 illuminated
• "Service Hybrid System" message on the dash
• Auto-Stop/Start feature is inoperative
• Harsh or jerky shifting, often described as a 'bump/jerk', especially when transitioning between electric and gas modes or during low-speed acceleration.
🎬 Watch: How to diagnose and fix a jerky transmission
• Hesitation or sudden acceleration at low speeds

Most Likely Causes

1. Damaged Wiring or Poor Connection 🔴 High Probability As identified in GM TSB #PIP4873A, the wiring harness between the Hybrid Powertrain Control Module (HPCM) and the auxiliary transmission fluid pump control module is the primary failure point. A forum user specifically identified the connectors under the 12V battery as a weak spot, where a pin can overheat from high current, causing a poor connection.
   How to confirm: Perform a thorough visual inspection of the wiring harness for any signs of chafing, breaks, or corrosion. Pay close attention to the connectors for the pump and module, which are located under the 12V battery. Check for loose, backed-out, or overheated/discolored terminals. Use a multimeter to test for continuity and check for loose terminals at the HPCM and pump module connectors.
   Typical fix: Repair the specific damaged wire or replace the faulty connector terminal. In some cases, cleaning the connector pins and ensuring a tight fit is sufficient. For 2008-2009 models, updated connector pigtails may be required if replacing the module or pump.
   Est. part cost: $10-$100 for wiring repair supplies or connector pigtails.

Rare But Worth Checking

• Failed Auxiliary Transmission Fluid Pump Control Module: This is the next most likely cause if the wiring is confirmed to be in perfect condition. TSB #PIP4873A suggests suspecting the module after wiring checks are complete. The OEM part number is 24261817, which supersedes several previous part numbers. Note that for 2008-2009 models, replacing this module also requires ordering connector pigtails (P/N 24259589 and 24259590).
• Failed Auxiliary Transmission Fluid Pump: This is a rare cause for this specific code combination on this vehicle. GM explicitly warns technicians in TSB #PIP4873A not to replace the pump until all other diagnostics have been performed. The original part number was 19168291, superseded by 19207983.
• Failed Hybrid Powertrain Control Module (HPCM): This is extremely unlikely and should only be considered after all other possibilities, including wiring, the pump module, and the pump itself, have been definitively ruled out.

Diagnosis Steps

1. Scan for all Diagnostic Trouble Codes (DTCs). Note if P2797 is present with P0C2B.
2. Obtain and review GM Technical Service Bulletin #PIP4873A. This document is critical for correct diagnosis.
3. Follow the TSB's primary instruction: DO NOT replace the auxiliary transmission pump.
4. Locate the wiring harness that runs between the Hybrid Powertrain Control Module (HPCM) and the auxiliary transmission fluid pump control module. A key inspection point is the set of connectors located under the 12V battery.
5. Disconnect the connectors and inspect all pins for signs of overheating (discoloration), corrosion, or damage. Check for good pin tension.
6. Perform a detailed visual inspection of the entire harness for any signs of physical damage, such as chafing, melting, or corrosion.
7. If no visual faults are found, use a digital multimeter and the vehicle's wiring diagram to perform continuity, resistance, and short-to-ground tests on each wire in the circuit.
8. Repair any wiring or terminal faults found. This may involve cleaning terminals, replacing a connector pigtail, or repairing a broken wire.
9. If and only if all wiring and connections are confirmed to be 100% intact, proceed with diagnostics for the auxiliary transmission fluid pump control module itself, as per the TSB.

Parts You'll Likely Need

• Wiring Repair Supplies — The most common cause is a wiring or connector fault, which is fixed by repairing the existing harness.
  Trusted brands: Delphi, ACDelco
  OEM price range: $20-$100 for connector pigtails if needed
  Aftermarket price range: $10-$50 for wire, terminals, and heat shrink
• Auxiliary Transmission Fluid Pump Control Module (OEM #24261817) — This is the most likely component to have failed if the wiring is confirmed to be good.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $120-$190
  Aftermarket price range: N/A
• Connector Pigtails (for 2008-2009 models) (OEM #24259589, 24259590) — Required per TSB PIP4833E if replacing the control module on a 2008 or 2009 model year vehicle to adapt to the updated module design.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $40-$80 per pigtail
  Aftermarket price range: N/A

Related Codes That Often Appear With This One

• P0C2B — This code, for the 'Auxiliary Transmission Fluid Pump Control Module Feedback Signal', is often set alongside P2797. TSB #PIP4873A directly addresses the diagnosis for when these two codes appear together, pointing to a wiring or module fault, not a pump fault.
• P0AC4 — This code, 'Hybrid Powertrain Control Module Requested MIL,' is a general code indicating that the hybrid module has detected a fault and requested the Check Engine Light to be turned on. It will almost always be present with more specific codes like P2797.

Technical Service Bulletins (TSBs) & Recalls

• PIP4873A: "Information Diagnosing DTC P0C2B" - This is the primary document for this issue. It advises that P2797 with P0C2B is likely a wiring or pump control module issue, not a pump failure, and instructs technicians to inspect wiring between the HPCM and the auxiliary pump module.
• PIP4833E: "Auxiliary Transmission Fluid Pump (ATFP) Control Module And Pump Parts Restriction" - This bulletin provides the specific part numbers for the pump (19207983) and module (24261817). Crucially, it also lists the required connector pigtails for 2008-2009 models when replacing these components.

Platform-Specific Known Issues

• The 2008-2013 GM Hybrid trucks and SUVs are subject to TSB #PIP4873A, which specifically identifies a wiring issue as the primary cause for DTC P2797 (especially with P0C2B) and warns against unnecessarily replacing the auxiliary transmission pump.
• A user on Tahoe Yukon Forum reported a successful fix by simply unplugging, cleaning, and reconnecting the pump/module connectors under the battery, suggesting a poor connection from an overheated pin is a specific failure mode.

Mechanic-Grade Diagnostic Values

• Auxiliary Pump Speed Deviation (Scan Tool) — expected: < 500 RPM difference between commanded and actual speed.. Failure: A difference greater than 500 RPM for 4 seconds or more will set DTC P2797.
• Ignition Voltage at ATFP Control Module — expected: 8-18 Volts. Failure: Voltage outside this range indicates a power supply or ground circuit issue that must be fixed before condemning the module or pump.
• Voltage on Transmission Auxiliary Oil Pump Control Circuit — expected: 11-13 Volts (at PIM connector X1 terminal 3 to ground). Failure: Voltage below this range can indicate an open or short to ground in the control circuit.
• ATFP Control Module Temperature (Scan Tool) — expected: Below 115°C (239°F). Failure: A fault status of 'ATFPCM Over temp' or 'ATFPCM Hot' indicates the module is overheating, which could be an internal fault if the case temperature is not actually elevated.
• ATFP Motor Current during start-up (Scan Tool) — expected: Less than 20 Amps. Failure: A current draw of more than 20 Amps during pump start-up will trigger an 'Unable to Start' fault status, pointing to a seized pump or high resistance.

Hidden / Shadow Codes Worth Checking

• Aux. Trans. Fluid Pump Fault Status (Scan Tool Parameter): The ATFP control module reports its internal diagnostic status to the HPCM, which can be viewed with a scan tool. These are not P-codes but provide deeper insight. (see via GM Tech 2 or GDS2 scan tool, under HPCM data.)
• Current High/Lo: Indicates the ATFP control module has monitored motor current that is outside the normal range for a given motor speed. Points to possible low fluid, bad wiring, or a damaged pump motor. (see via GM Tech 2 or GDS2 scan tool.)
• Current Fault: Indicates an internal ATFP control module fault exists; external circuits are not involved. This status directly points to replacing the ATFP control module. (see via GM Tech 2 or GDS2 scan tool.)
• No PWM Response: Indicates the HPCM does not detect the feedback signal from the ATFP Control Module. The service manual directs technicians to diagnose DTC P0C2B when this is seen. (see via GM Tech 2 or GDS2 scan tool.)

Scan Tool Commands That Help

• GM Tech 2 / GDS2: Auxiliary Transmission Fluid Pump Control — During diagnosis, a technician can command the auxiliary pump speed to 50% to verify its operation. While the pump is commanded on, the technician can monitor for noise, stalling, and check the 'Aux. Trans. Fluid Pump Fault Status' displays for any active faults.

Wiring & Ground Locations

• Auxiliary Pump & Module Connectors — Under the hood, located just below and to the right (passenger side) of the 12V starting battery. There are two main connectors in this area with larger gauge wires.. This is a known failure point. High current can cause pins in these connectors to overheat, leading to a poor connection, increased resistance, and the setting of P2797 and P0C2B. A visual inspection for discolored or melted plastic and checking pin tension is a critical first step.

Real Owner Repair Stories

• Tahoe Yukon Forum user 'lt1gmc' (2009 GMC Hybrid) — Intermittent 'bump/jerk' issue, likely with codes P2797/P0C2B.
  ❌ Tried (didn't work) Initially, just unplugging and replugging the connectors would fix it temporarily for a few thousand miles.
  ✅ What actually fixed it The final fix was to thoroughly clean the pins on the auxiliary pump and module connectors located under the 12V battery. The user noted that high current overheats one of the pins, causing a bad connection.
• Tahoe Yukon Forum user 'ChuckC' (GMC Hybrid Truck (year not specified)) — Jerking sensation when switching between hybrid/engine modes, pauses in acceleration, sudden accelerations at low speeds. Codes P2797, P0C2B, and P0AC4 were present.
  ❌ Tried (didn't work) Not specified; user went straight to the TSB-recommended repair.
  ✅ What actually fixed it Replaced the auxiliary transmission fluid pump control module (P/N 24261817) and two required adapter harnesses for older models (P/N 24259589 and 24259590). The total cost for parts and labor was $637.

When the Usual Fixes Don't Work

• While TSB PIP4873A correctly steers technicians away from replacing the pump, it points next to the control module if wiring checks out. However, at least one owner has documented a permanent fix achieved by simply cleaning the high-current connector pins under the battery, which had become a point of high resistance from overheating. This suggests that even before replacing the module, a meticulous cleaning and tensioning of the existing connectors is a valid repair step that can resolve the fault without replacing any parts.

OEM Part Supersession History

• 29546636, 29547550, and others → 24261817 — Part consolidation and potential design updates.
  Heads up: The updated module 24261817 has different connectors than the 2008-2009 harnesses. When installing this module on a 2008-2009 vehicle, adapter pigtails P/N 24259589 and 24259590 are required.
• 19168291 → 19207983 — Part consolidation and potential design updates.
  Heads up: When installing the newer pump (19207983) on a 2008-2009 vehicle that still has its original control module, adapter pigtail P/N 24259588 is required.

Model Year Variations Within This Range

• 2008-2009: The original Auxiliary Transmission Fluid Pump and Control Module used different electrical connectors than the parts used from 2010-2013. GM TSB #10-07-30-009 and PIP4833E detail this change. As a result, when replacing either the pump or module on a 2008-2009 model with current service parts (which are the 2010+ design), specific adapter harnesses must be ordered to make the connections.