U0415 on 2015-2019 GMC Sierra 3500: Invalid ABS Data Causes and Fixes

What's Unique About the 2015-2019 Gmc SIERRA 3500

For this generation of GMC Sierra (K2XX platform), the U0415 code is strongly linked to specific, well-documented issues. GM has issued multiple Technical Service Bulletins (TSBs) that point technicians away from immediately replacing the expensive ABS module. Instead, they highlight common, less-obvious causes like low brake fluid causing erratic sensor readings during vehicle motion (TSB #PIT5490B), and known chafe points where wiring harnesses can get pinched or corroded under the door sills (TSB #PIT5457D) and behind the dashboard (TSB #PIT5288G).

Diagnostic Flowchart

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

Symptoms You May Notice

• ABS warning light on
• Traction control or StabiliTrak warning light on
• "Service Trailer Brake" message in the driver information center (DIC)
• Check Engine Light may be on
• Inoperative cruise control
• Wipers inoperative or dead battery (in cases of severe wiring shorts) [Bulletin #PIT5288G]
• "Steering Assist is Reduced Drive With Care" message may appear

Most Likely Causes

1. Low Brake Fluid Level 🔴 High Probability A specific TSB (#PIT5490B) notes the fluid level sensor is sensitive. During turns, braking, or acceleration, fluid can slosh in a low reservoir, causing the sensor to send a momentary 'low' signal to the EBCM. The Chassis Control Module receives this intermittent data via the CAN bus, flags it as invalid, and sets U0415, often with the 'Service Trailer Brake' message.
   How to confirm: Visually inspect the brake fluid level in the master cylinder reservoir. If it is near the 'MIN' line, this is the likely cause. A professional scan tool (like GM's GDS2) can monitor the 'Brake Fluid Level Sensor' parameter in the EBCM data list to confirm it reads 'Low'.
   Typical fix: Fill the master cylinder reservoir to the 'MAX' line using the correct DOT 3 or DOT 4 brake fluid. Clear the codes and test drive. Crucially, inspect the brake system for the cause of the low fluid, such as worn pads or leaks.
   Est. part cost: $5-$15
2. Damaged/Corroded Wiring Under Door Sill Plates 🟡 Medium Probability TSB #PIT5457D specifically calls out this location. The wiring harness running in the channel under the driver and passenger sill plates is susceptible to moisture from water intrusion, leading to corrosion and high resistance, especially on the Communication Enable circuit (5986). Physical damage from getting kicked or having items dropped on it is also common.
   How to confirm: Remove the driver and passenger plastic sill plates and lift the carpet/flooring to visually inspect the wiring harness for any signs of green or white corrosion (verdigris), chafing, pinched wires, or previous poor repairs. Specifically check Splice J365 under the passenger front sill plate. 🎬 See this walkthrough for finding and fixing corroded sill plate wiring.
   Typical fix: Repair the damaged section of the wire harness. This involves cutting out the corroded section, splicing in new wire (soldering is preferred), and using adhesive-lined heat-shrink tubing to protect the repair from future moisture intrusion.
   Est. part cost: $10-$50
3. Pinched Wire Harness at Left Instrument Panel ⚪ Low Probability TSB #PIT5288G identifies a potential issue where the wire harness near the left instrument panel can become pinched by the park brake pedal bracket. This can cause a short or open circuit, leading to various communication codes, including U0415.
   How to confirm: Inspect the wiring harness behind the left side of the dashboard, near the fuse block and parking brake pedal area, for any signs of being pinched, chafed, or rubbing against sharp metal edges of brackets.
   Typical fix: Free the pinched harness and repair any damaged wires as needed. Reroute the harness to prevent future damage, possibly using a zip tie or protective conduit.
   Est. part cost: $10-$50
4. Failing Electronic Brake Control Module (EBCM) ⚪ Low Probability While possible, internal failure of the EBCM is less common than wiring or fluid level issues for this specific code on this truck. The module's location on the driver's side frame rail does expose it to the elements, but wiring issues are a more frequent point of failure.
   How to confirm: This is typically diagnosed by exclusion. If the brake fluid level is correct and all related wiring (sill plates, dash harness), grounds (EBCM frame ground), and connectors have been thoroughly inspected and tested, the module itself becomes the primary suspect.
   Typical fix: Replace the EBCM. The new module will require programming to the vehicle's VIN with a factory-level scan tool like the GM GDS2.
   Est. part cost: $264-$700

Rare But Worth Checking

• Poor EBCM Ground Connection: The main ground for the EBCM is typically on the frame rail under the driver's door, often near the module itself. 🎬 Watch: How to locate and clean a corroded EBCM frame ground. Corrosion or a loose connection at this point can cause erratic behavior and communication faults, leading to U0415.
• Faulty Trailer Brake Control Module (TBCM): Since the 'Service Trailer Brake' message is a key symptom, a fault within the separate Trailer Brake Control Module itself or its wiring can sometimes be the root cause, sending conflicting information that results in a U0415 code.
• Loose or Corroded Main Ground G218: TSB PIT5405C points to ground G218, located on the left side of the instrument panel support, as a source of numerous electrical issues. An improperly seated dash insulator mat can get trapped under the ground eyelet, causing high resistance and a host of communication DTCs.

Diagnosis Steps

1. Check the brake fluid level in the master cylinder. Top it off if it is low. This is the simplest and a very common fix.
2. Use a professional scan tool (e.g., GM GDS2) to read all codes from all vehicle modules, not just the engine computer. Note which modules are reporting the U0415 code.
3. If the fluid level is correct, the next step is a thorough visual inspection of the known problem wiring areas.
4. Remove the driver and passenger side door sill plates and inspect the wiring harnesses in the channels for corrosion, damage, or previous poor repairs, as per TSB #PIT5457D. Pay close attention to the Communication Enable circuit 5986.
5. Inspect the wiring harness behind the left side of the instrument panel for any signs of being pinched or chafed by the parking brake bracket, as per TSB #PIT5288G.
6. Inspect the main ground connection for the EBCM, typically located on the frame rail under the driver's side, for tightness and corrosion.
7. If no wiring issues are found, test the CAN bus wiring for proper resistance (typically 60 ohms) between pins 6 and 14 at the diagnostic port. A reading of 120 ohms suggests an open circuit or a missing terminating resistor.
8. If all wiring and connections test good, the EBCM itself may be faulty. This is a diagnosis by elimination.

Parts You'll Likely Need

• Brake Fluid (DOT 3 or DOT 4) — The most common cause for U0415 on these trucks is a low brake fluid level causing an erratic sensor signal, as documented in TSB #PIT5490B.
  Trusted brands: ACDelco, Prestone, Bosch
  OEM price range: $10-$20
  Aftermarket price range: $5-$15
• Electronic Brake Control Module (EBCM) (OEM #84256781 (supersedes 84256789, 23355954, 84074960, 84074957)) — If all wiring and fluid level issues are ruled out, the module itself may have failed internally, causing it to send invalid data.
  Trusted brands: ACDelco (GM Original Equipment)
  OEM price range: $264-$700

Related Codes That Often Appear With This One

• U0077 — Indicates a general High Speed Communication Bus issue, often set alongside U0415 when a wiring harness is the root cause. It is mentioned in TSBs #PIT5288G and #PIT5457D.
• U0121 — Means 'Lost Communication With Anti-Lock Brake System (ABS) Control Module'. This indicates a more severe communication breakdown and often points to the wiring issues cited in TSB #PIT5457D.
• U0126 — Lost Communication With Steering Angle Sensor Module. This sensor's data is critical for the stability control system, and a network fault can interrupt its signal. It is mentioned in TSB #PIT5288G and #PIT5457D.
• U0140 — Lost Communication With Body Control Module. This can be set when the BCM itself has issues or when a major wiring harness problem affects multiple modules.

Technical Service Bulletins (TSBs) & Recalls

• PIT5288G: Addresses various electrical issues, including U0415, caused by a pinched wire harness in the left instrument panel.
• PIT5457D: Points to loss of communication codes, including U0415, caused by damaged wiring under the driver and passenger sill plates.
• PIT5490B: Specifically links the 'Service Trailer Brake' message and code U0415 to a low brake fluid level.

Platform-Specific Known Issues

• TSB #PIT5490B: A 'Service Trailer Brake' message with code U0415 is frequently caused by the brake fluid level being near the minimum mark. Topping off the fluid is the specified fix.
• TSB #PIT5457D: Communication codes, including U0415, can be caused by an open, damaged, or corroded wire in the harness located under the driver and passenger sill plates. This is a very common real-world failure point discussed in forums.
• TSB #PIT5288G: A pinched wire harness near the parking brake pedal bracket is a known cause for U0415 and other seemingly unrelated electrical faults like wiper failure.
• Real Owner Experience: Sill Plate Corrosion: Multiple owners on forums like gm-trucks.com report finding green, corroded wires in the harness that runs along the driver's side floor under the plastic sill plate. After experiencing the 'Service Trailer Brake' and 'Service Stabilitrak' messages with code U0415, they found that repairing these corroded wires resolved the issue completely. This corroborates the fix described in TSB #PIT5457D.

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Resistance — expected: Approximately 60 Ohms. Failure: A reading of ~120 Ohms indicates an open circuit or one of the two terminating resistors is offline. A reading near 0 Ohms indicates a short between the CAN High and CAN Low wires.
• Communication Enable Circuit 5986 Voltage — expected: Approximately 12 Volts (battery voltage). Failure: Low or no voltage indicates an open or high resistance in the circuit, often under the driver's/passenger's sill plate.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6) should average ~2.7V. CAN Low (Pin 14) should average ~2.3V. The sum should be ~5V.. Failure: Voltages that are stuck high, low, or do not switch indicate a short to power, ground, or a module pulling the bus down.

Scan Tool Commands That Help

• GM GDS2: EBCM Data List > 'Brake Fluid Level Sensor' parameter — To confirm if the brake fluid level sensor is intermittently reporting 'Low' status, which is a primary cause of U0415 on these trucks as per TSB #PIT5490B.
• GM GDS2: Module Programming & Setup — Required after replacing the Electronic Brake Control Module (EBCM) or Power Steering Control Module. The new module must be programmed with the vehicle's VIN and then a setup procedure must be run to calibrate it to the vehicle's specific options.

Wiring & Ground Locations

• Circuit 5986 — Runs in the harness under the driver and passenger door sill plates.. This is the 'Communication Enable' circuit. TSB #PIT5457D identifies it as a common point for opens or high resistance due to corrosion, which prevents the EBCM and other modules from 'waking up' and communicating, leading to U-codes.
• Splice J365 — Located in the wiring harness under the passenger front sill plate.. This is a known failure point within Circuit 5986, specifically called out as a place to inspect for corrosion from water intrusion.
• EBCM Ground — On the frame rail under the driver's door, near the EBCM itself.. A loose or corroded main ground for the ABS module can cause erratic operation and communication faults like U0415. This is a fundamental check before replacing the module.
• G218 — A ground point located on the left-hand instrument panel support structure, behind the dash.. TSB PIT5405C identifies this ground as a potential cause for a wide range of electrical issues, including communication DTCs. The dash insulator mat can get trapped under the connection, causing high resistance.
• Underhood Fuse Block Fuses — In the main fuse block under the hood, next to the brake fluid reservoir.. For 2018+ models, fuses F3 (60A), F19 (10A), and F25 need to be checked for the ABS module. For 2014-2017 models, it's fuses F3, F19, and F25 in slightly different locations. A blown fuse will cut power to the module.

Real Owner Repair Stories

• YouTube user '59 Motorsports' (2016 GMC Sierra) — "Service Trailer Brake" message on the dash.
  ❌ Tried (didn't work) Initially suspected a blown fuse but found them to be good.
  ✅ What actually fixed it Replacing the Trailer Brake Control Module (the switch assembly in the dash) resolved the issue. The user noted that on a different truck, a blown #2 30-amp fuse for the trailer battery system was the cause.

OEM Part Supersession History

• 23355954, 84074957, 84074960, 84256789 → 84256781 — Standard part evolution for reliability or manufacturing updates.
  Heads up: Part 84256781 is specified for vehicles with hydraulic power brakes (RPO JD9) and without adaptive cruise control. Always verify fitment with VIN before ordering.

Model Year Variations Within This Range

• 2014-2017 vs 2018-2019: The specific fuse locations for the ABS module in the underhood fuse block differ slightly between these year groups, although the functions are the same.