P2636 on 2015-2017 Chevrolet Silverado 3500: Fuel Transfer Pump & Gauge Fixes

What's Unique About the 2015-2017 Chevrolet SILVERADO 3500

This issue is highly specific to the 2015-2016 Silverado and Sierra 3500 Chassis Cab models with the 6.6L LML Duramax engine and dual tanks. The problem was so prevalent that GM issued a specific emissions recall (17067) to fix it. The recall involved replacing fuel line connections to allow the rear tank to supply the engine directly (in addition to the front tank) and reprogramming the ECM. Additionally, several Technical Service Bulletins (TSBs) address related symptoms, like kinked fuel lines (PIT5510D) and false codes set by refueling with the ignition on (PIT5208A), making this a well-documented platform-specific problem.

Diagnostic Flowchart

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

Symptoms You May Notice

• Fuel gauge suddenly drops to empty.
• Low fuel level indicator illuminates.
• Check Engine Light (Malfunction Indicator Lamp) is on.
• Engine stalls while driving, potentially without warning.
• Vehicle is unable to restart after stalling.
• Grinding or knocking noise from under the truck if the front tank over-pressurizes and contacts the driveshaft (related issue on some dual-tank models).

Most Likely Causes

1. Restricted or Kinked Fuel Transfer Line 🔴 High Probability GM TSBs PIT5510D and PIT5510C specifically note that the fuel line between the tanks can become kinked, even during installation of a replacement part, which restricts flow and triggers the code. The TSB warns that the protective conduit can hide the kink.
   How to confirm: Visually inspect the fuel transfer line that runs between the two tanks. The protective conduit may need to be slid back to check the plastic line underneath for kinks or damage, particularly near bends and frame crossmembers.
   Typical fix: Replace the kinked or damaged fuel transfer line. GM issued a redesigned hose kit (Part No. 84525925) as part of recall 17067 to address this. An earlier kit, part number 84214102, is also mentioned in TSBs.
   Est. part cost: $50-$100
2. Failed Rear (Transfer) Fuel Pump 🟡 Medium Probability → Shop Fuel Pump The pump itself can fail electrically or mechanically, preventing it from moving fuel. An owner complaint cited a transfer pump failure that led to a stall. A forum member reported P2636 returning two years after the recall fix, suspecting the pump had failed despite being commanded on by the scan tool.
   How to confirm: Perform a fuel transfer pump flow test as described in TSB PIT5510. Command the pump on with a scan tool for 2 minutes; it should transfer more than 2.6 liters (0.70 gallons) of fuel. 🎬 Watch: Troubleshooting dual tank fuel transfer failures and leaks. If no fuel moves and the pump has power and ground, it has failed.
   Typical fix: Replace the fuel transfer pump module in the rear fuel tank. This requires dropping the tank or removing the truck bed for access. 🎬 Watch: Step-by-step guide for replacing the fuel pump module assembly.
   Est. part cost: $150-$400
3. Refueling with Ignition On 🟡 Medium Probability A well-documented software quirk can cause the fuel monitoring system to get confused if the ignition is on or the engine is running during refueling. This can set a false P2636 code, as noted in TSB PIT5208A. The TSB explicitly states to question the owner on refueling habits before performing diagnostics.
   How to confirm: This is a procedural issue. If the code only appears immediately after refueling, ask about the refueling habits. The fix is to clear the code and see if it returns after refueling with the vehicle turned completely off.
   Typical fix: No parts needed. Advise the driver to always turn the ignition fully off before refueling.
   Est. part cost: $0
4. Faulty Fuel Pump Control Module (FPCM) or Wiring ⚪ Low Probability → Shop Fuel Pump On many GM trucks, the FPCM is mounted on the frame rail, where it's exposed to moisture and corrosion, leading to failure. This can cause a loss of communication or erratic pump operation. The location is often on a crossmember near the spare tire.
   How to confirm: Inspect the FPCM and its connector for corrosion or damage. Check for related codes like U0109 (Lost Communication With FPCM). Check for power at the FPCM fuse (typically a 20A fuse in the underhood fuse box) and signal from the ECM.
   Typical fix: Replace the Fuel Pump Control Module and repair any corroded wiring or connectors. Some aftermarket modules do not require programming, but OEM parts often do.
   Est. part cost: $80-$150

Rare But Worth Checking

• Plugged Rear Fuel Tank Vent: → Shop Fuel Tank

Diagnosis Steps

1. Verify the vehicle is a Chassis Cab model with the 6.6L LML engine and dual fuel tanks (RPO N2N), as this code is highly specific to this configuration.
2. Check GM's Global Warranty Management system using the VIN to see if recall 17067 is open. If so, have the recall performed by a dealer, which involves a new hose kit and an ECM reprogram.
3. Question the driver about refueling habits. If they refuel with the ignition on, clear the code, refuel with the truck off, and test drive before continuing.
4. Scan for other codes. U0109 or P069E strongly suggest a problem with the Fuel Pump Control Module (FPCM) or its wiring.
5. Inspect the FPCM and its connector (usually on a frame crossmember near the spare tire) for corrosion or damage.
6. Perform a fuel transfer pump flow test using a scan tool, as detailed in TSB PIT5510. Command the pump on for 2 minutes and measure the fuel transferred. It should be more than 2.6 liters (0.70 gallons).
7. If the flow test fails, inspect the fuel transfer line between the tanks for kinks or damage, as noted in TSB PIT5510D. Remember to slide back the protective conduit to see the line itself.
8. If the lines are clear but the pump does not run or flow is low, test for power and ground at the rear transfer pump connector. If power and ground are present but the pump doesn't run, the pump has failed.
9. Inspect the top of the rear tank for debris and check if the tank is deformed, which would indicate a plugged vent per TSB 19-NA-277.

Parts You'll Likely Need

• Fuel Tank Fill Hose Kit (OEM #84525925) — This is the official part kit from GM recall 17067, designed to fix the fuel transfer plumbing issue that causes P2636. It includes a new hose assembly, clamps, and a cap for the now-unused port on the front tank.
  Trusted brands: GM Genuine
  OEM price range: $50-$100
  Aftermarket price range: N/A
• Fuel Transfer Pump / Fuel Pump Module (Rear Tank) — If the pump itself fails the flow test and has proper power, it must be replaced. This was the cause of a stall in one owner complaint and is a common point of failure even after the recall is performed.
  Trusted brands: ACDelco, Delphi
  OEM price range: $250-$400
  Aftermarket price range: $150-$250
• Fuel Pump Control Module (FPCM) — Though less common for this specific TSB, FPCM failure is a frequent cause of fuel delivery codes on GM trucks due to its exposed location and susceptibility to corrosion.
  Trusted brands: ACDelco, Dorman
  OEM price range: $100-$150
  Aftermarket price range: $70-$150

Related Codes That Often Appear With This One

• U0109 — This code means 'Lost Communication With Fuel Pump Control Module. 🎬 See how to locate and inspect the fuel pump control module.' It often appears with P2636 if the FPCM has failed due to corrosion or internal faults.
• P069E — Indicates a fault was reported by the Fuel Pump Control Module itself, pointing directly to the FPCM as the likely source of the problem.

Technical Service Bulletins (TSBs) & Recalls

• 17067 (Emissions Recall)
• PIT5510D, PIT5510C, PIT5510B, PIT5510
• PIT5208A
• 19-NA-277

Platform-Specific Known Issues

• GM Product Emission Recall #17067 was issued for 2015-2016 models with the 6.6L diesel engine and dual tanks to correct an issue where fuel may not transfer from the rear to the front tank, causing P2636 and stalling. The fix involves replacing fuel line connections to allow the rear tank to also supply the engine directly and reprogramming the ECM.
• TSB #PIT5510D provides detailed instructions for diagnosing P2636 when the fuel gauge reads empty, focusing on a fuel transfer pump flow test and warning that kinked fuel lines (even on new parts) are a common cause of repeat failures.
• TSB #PIT5208A warns that a false P2636 code can be set if the vehicle is refueled with the ignition on or engine running, and advises this should be the first diagnostic question.
• TSB #19-NA-277 addresses a related but severe issue where a clogged rear tank vent can cause the tank to collapse under vacuum from the transfer pump, requiring tank and pump replacement.

Mechanic-Grade Diagnostic Values

• FPCM Connector Pin 1 (Black) to Chassis Ground — expected: < 1.0 ohm. Failure: High resistance indicates a corroded or broken ground connection at the frame rail.
• FPCM Connector Pin 13 (Dark Green/White wire) Voltage — expected: 12V for 2-6 seconds when key is first turned to 'ON' (ECM prime signal).. Failure: No voltage suggests a fault in the ECM or a break in the wire from ECM Pin 50.
• FPCM Connector Pin 15 (Pink wire) Voltage — expected: 12V+ with Ignition ON.. Failure: No voltage points to an issue with the ignition circuit or the FPCM fuse.
• FPCM Connector Pin 32 (Red/White wire) Voltage — expected: Constant Battery Voltage (12V+).. Failure: No voltage indicates a blown fuse (likely the 20A FSCM fuse, #21) or a break in the power wire.
• Fuel Transfer Pump Flow Rate — expected: Greater than 2.6 liters (0.70 gallons) transferred in 2 minutes.. Failure: Less than 2.6 liters indicates a weak pump or a restriction in the line.

Scan Tool Commands That Help

• GDS2 / Tech2: Fuel Transfer Pump ON/OFF — This is the primary bidirectional control used to manually activate the rear transfer pump to check for operation (audible hum) and to perform a fuel flow test without running the engine.
• GDS2: Fuel Pump Driver Control Module Configuration — This function is required after replacing the FPCM to program the new module to the vehicle. A known glitch may require manually selecting a different engine (e.g., 2.7L L3B) in GDS2 to make this function appear.

Wiring & Ground Locations

• Fuel Pump Control Module (FPCM) — On a frame crossmember under the vehicle, typically near or above the spare tire.. This location makes the module and its connector highly susceptible to corrosion from road salt and moisture, a common cause of failure leading to P2636 and U0109.
• FPCM Ground — A black wire bolted directly to the driver's side frame rail, near the FPCM.. This is the primary ground for the entire fuel pump circuit. Corrosion or a loose connection at this single point can cause intermittent or complete failure of the transfer pump, triggering a P2636 code even if the pump and module are good.
• ECM Connector (Pin 50) — The black connector at the Engine Control Module (ECM).. Pin 50 (Dark Green/White wire) is the source of the 'pump on' command signal from the ECM to the FPCM. Testing for voltage here can isolate a fault between a bad ECM or a broken wire.

Real Owner Repair Stories

• DuramaxDiesels.com forum user (2016 Chevrolet Silverado Chassis Cab) — Code P2636 returned two years after the recall kit was installed.
  ❌ Tried (didn't work) Visual inspection of the fuel line for kinks., Verifying the rear tank breather was open.
  ✅ What actually fixed it The user suspected the transfer pump itself had failed, even though it would run when commanded by a scan tool. The final resolution was to order and replace the transfer pump.

"I Checked Everything" — The Actual Cause

• A common scenario described in TSB PIT5510D is when a technician confirms the FPCM and transfer pump are working correctly, yet the P2636 code persists. The actual cause is often a kinked fuel transfer line between the two tanks, which is frequently missed because the kink is hidden under a protective conduit.

OEM Part Supersession History

• 84214102 → 84525925 — Part 84214102 was the hose kit specified in early versions of TSB PIT5510. Part 84525925 is the kit specified for the official Emission Recall 17067, which is the more comprehensive and final repair.

Model Year Variations Within This Range

• 2015-2016: The primary issue addressed by recall 17067 is specific to 2015-2016 model year Silverado and Sierra HD trucks with the LML engine and dual tanks (RPO N2N). While 2017 models share the platform, the recall documentation focuses on these two years.