U0415 on 2015-2019 GMC Yukon Denali: Causes for Invalid ABS Data

What's Unique About the 2015-2019 Gmc YUKON DENALI

On this specific GM truck platform (GMT K2XX), the U0415 code is uniquely tied to several well-documented issues in official Technical Service Bulletins (TSBs). Unlike a generic interpretation that might immediately point to a failed ABS module, for the Yukon Denali and its platform mates, the most likely causes are much simpler. These include low brake fluid causing erroneous sensor readings during vehicle motion, and specific wiring harnesses being pinched or corroded in known locations like under the door sills or behind the instrument panel.

Diagnostic Flowchart

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

Symptoms You May Notice

• "Service Trailer Brake" me 🎬 See this walkthrough for fixing the Service Trailer Brake message.ssage on the Driver Information Center (DIC).
• "Service StabiliTrak" message.
• ABS warning light illuminated.
• Traction control warning light illuminated.
• Erratic speedometer and tachometer behavior, such as needles suddenly maxing out.
• In some cases with related wiring faults, wipers may be inoperative, the radio/display may be blank, or the battery may die (per TSB #PIT5288H).

Most Likely Causes

1. Low Brake Fluid Level 🔴 High Probability → Shop Brake Fluid According to GM TSB #PIT5490B, as the vehicle brakes, accelerates, or turns, brake fluid near the 'minimum' level can slosh around. This causes the fluid level sensor to momentarily send a 'low fluid' signal to the Electronic Brake Control Module (EBCM), which then sends invalid data out to the Chassis Control Module, triggering the U0415 code and often a 'Service Trailer Brake' message.
   How to confirm: Visually inspect the brake fluid level in the master cylinder reservoir. If it is at or near the 'MIN' line, this is the likely cause. A scan tool can also monitor the 'Brake Fluid Level Sensor' parameter, which should read 'OK' and not fluctuate to 'Low'.
   Typical fix: Fill the master cylinder brake fluid reservoir to the 'MAX' line. It is also critical to inspect for the cause of the low fluid, such as worn brake pads or a leak in the brake system. Inspect the rear of the master cylinder for leaks into the brake booster.
   Est. part cost: $5-$15 for DOT 3 or DOT 4 brake fluid.
2. Damaged or Corroded Wiring Harness 🟡 Medium Probability GM has identified two common problem areas. TSB #PIT5457D points to the harness under the driver and passenger sill plates being susceptible to moisture and corrosion from water brought in on footwear. TSB #PIT5288H identifies a pinch point for the wire harness between the left I/P dash mounting bracket and the body, sometimes near the parking brake pedal assembly.
   How to confirm: Visually inspect the specified wiring harnesses. For the sill plates, remove the trim and check 🎬 Watch: How to remove door sill plates to inspect wiring. for green or white corrosion on wires and connectors. For the instrument panel, inspect the harness from under the dash for any signs of being crushed or chafed against the metal bracket; the harness should move freely.
   Typical fix: Repair the damaged, corroded, or open section of the wire harness and protect it from future damage. This may involve soldering, using new connectors, and re-routing the harness to prevent repeat pinching or water exposure.
   Est. part cost: $10-$50 for wiring repair supplies.
3. Failing ABS Control Module (EBCM) ⚪ Low Probability → Shop ABS Control Module
   How to confirm: This should only be considered after all other possibilities, especially low fluid and wiring issues, have been ruled out. Diagnosis requires an advanced scan tool to attempt to communicate directly with the module and verify it has proper power and ground.
   Typical fix: Replace the ABS control module. The new module will require programming to the vehicle's VIN.
   Est. part cost: $200-$700 for an OEM ACDelco module, depending on the specific part number and vehicle options.

Rare But Worth Checking

• Faulty Wheel Speed Sensor: → Shop ABS Wheel Speed Sensor A single wheel speed sensor sending erratic data to the ABS module can cause the module to output invalid data to the rest of the network. This would typically be accompanied by a specific wheel speed sensor code (e.g., C0035-C0050).
• Weak Battery or Poor Ground Connection: → Shop Vehicle Battery A failing battery or high resistance in battery cables or grounds can cause low voltage to various modules, leading to a host of communication codes, including U0415. In one forum post, a user with a 'Service Trailer Brake' message found that replacing a dying battery resolved the issue. GM TSB PIT5405C also points to a poor BCM ground at G218 🎬 Watch: How to locate and fix the G218 ground issue. as a cause for numerous electrical issues.

Diagnosis Steps

1. Check and record any other DTCs stored in any module. The presence of other communication codes can point to a specific wiring harness issue.
2. Visually inspect the brake fluid level in the master cylinder. If low, top it off to the MAX line, clear codes, and test drive, including some hard stops and turns. If the code does not return, inspect the brake system for leaks or worn pads.
3. If the fluid level is OK, perform a battery and charging system test. A weak battery can cause numerous communication faults.
4. Remove the driver and passenger front door sill plates and inspect the wiring harnesses in the channel for any signs of moisture, green/white corrosion, damage, or previous improper repairs, as noted in TSB #PIT5457D.
5. Inspect the wire harness on the left side of the instrument panel, from underneath the dash. Check for signs of it being pinched or chafed by the metal I/P mounting bracket, as noted in TSB #PIT5288H. Ensure the harness can move freely.
6. Using a scan tool, monitor the 'Brake Fluid Level Sensor' parameter in the EBCM data list to ensure it reads 'OK' and is not fluctuating during vehicle movement.
7. Test the CAN bus network wiring for proper resistance (typically 60 Ohms with the battery disconnected) and check for shorts to power or ground between the EBCM and other modules.
8. If all wiring, fluid levels, and power/grounds are confirmed to be good, suspect a faulty ABS control module.

Parts You'll Likely Need

• Brake Fluid — Low fluid level is a primary cause for this code on this vehicle, as documented in TSB #PIT5490B.
  Trusted brands: ACDelco, Prestone
  OEM price range: $10-$20
  Aftermarket price range: $5-$15
• Electronic Brake Control Module (EBCM) (OEM #84778360 (supercedes 23154727, 23223286, 23154723, 84601113, and is replaced by 85698742)) — If wiring and fluid levels are confirmed to be good, the module itself may have an internal fault causing it to send corrupt data. Part numbers are frequently superseded; always verify with VIN.
  Trusted brands: ACDelco (GM Original Equipment)
  OEM price range: $200-$700
  Aftermarket price range: $200-$500

Related Codes That Often Appear With This One

• U0077, U0121, U0126, U0131, U0139, U0401, U0428 — These codes, cited in TSB #PIT5457D, indicate a general loss of communication with various chassis and steering modules. Their presence alongside U0415 strongly suggests a network wiring issue, such as the harness under the sill plates.
• B3101, B144C, C0710, C0544, U1548, U1549, U154A, U0151, U0126, U0077, U0028, U0029 — This group of codes, from TSB #PIT5288H, points to a widespread electrical issue caused by the pinched harness in the instrument panel, affecting multiple systems including passive entry, audio, and displays.

Technical Service Bulletins (TSBs) & Recalls

• PIT5490B: Diagnostic tip for a 'Service Trailer Brake' message with DTC U0415, pointing to low brake fluid as the cause.
• PIT5457D: Addresses loss of communication with various modules due to a damaged wire harness under the sill plates.
• PIT5288H: Relates various electrical faults to a pinched harness in the instrument panel.

Platform-Specific Known Issues

• TSB #PIT5490B: A 'Service Trailer Brake' message accompanied by U0415 is frequently caused by the brake fluid level being near the minimum mark. Topping off the fluid is the specified fix.
• TSB #PIT5457D: A loss of communication with multiple modules, including the EBCM (setting U0415), can be caused by a damaged or corroded wiring harness located under the driver and passenger door sill plates.
• TSB #PIT5288H: A wide range of electrical codes, including U0415, can be triggered by a pinched wire harness located in the left instrument panel between the mounting bracket and the body.

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Resistance — expected: Approximately 60 Ω (with battery disconnected, measured between pins 6 and 14 of the OBD-II port).. Failure: A reading of 120 Ω indicates a missing termination resistor or an open in the bus. A reading near 40 Ω suggests a third, unwanted resistor is present. A reading significantly lower than 60 Ω can indicate a shorted wire or a failed module transceiver.
• Communication Enable Circuit 5986 Voltage — expected: Approximately 11-12 volts when the BCM is awake (e.g., ignition on).. Failure: No voltage or low voltage (below 11V) when load-tested with a small bulb (like a 194 lamp) indicates high resistance or an open in the circuit, as described in TSB PIT5457D. The BCM will shut down this circuit if it draws more than 0.88 amps (e.g., a short to ground).
• Module Ground Resistance — expected: Less than 5 mΩ.. Failure: High resistance at a module's ground connection indicates a poor ground, which can cause a variety of communication issues.

Scan Tool Commands That Help

• GDS2 (via ACDelco TDS / Techline Connect): Replace and Program Module — This function is required after replacing the Electronic Brake Control Module (EBCM). The new module must be programmed with the vehicle's VIN and specific software configuration to function correctly and communicate with other modules on the network.
• GDS2 (via ACDelco TDS / Techline Connect): Clear All DTCs — After performing a repair, such as topping off brake fluid or fixing a wiring issue, all codes in all modules should be cleared. This is necessary to confirm the repair was successful and to ensure no lingering fault codes cause other systems to remain in a disabled state.

Wiring & Ground Locations

• G218 — Inside the cabin, on the driver's side, under the dash panel near the A-pillar and left front speaker.. This is a primary ground for the Body Control Module (BCM). TSB PIT5405C identifies a poor connection here (often due to the dash insulator mat being trapped under the ground terminal) as a cause for widespread electrical issues and communication faults, as the BCM orchestrates much of the vehicle's network activity.
• Left I/P Dash Mounting Bracket Harness Pinch Point — Under the driver's side dash, where the main dash harness passes the metal instrument panel mounting bracket, near the parking brake pedal assembly. It is best viewed from below after removing the end cap of the dashboard.. TSB PIT5288H specifically calls this location out as a common point for the harness to be pinched, causing shorts or opens in multiple circuits, including CAN bus lines, leading to a host of communication codes including U0415.
• Sill Plate Harness / Splice J365 — The wiring harness runs in a channel under the driver's and passenger's front door sill plates. TSB PIT5457D specifically mentions Splice J365, located under the passenger front sill plate, as a potential point of failure.. This harness is prone to water damage and corrosion from moisture brought in by occupants. A failure in the 'Communication Enable Circuit 5986' within this harness can prevent the EBCM and other modules from 'waking up', leading to loss of communication codes like U0415.
• EBCM Body Harness (at transmission mount) — The harness branch leading to the EBCM may be routed incorrectly, allowing it to rub against a transmission mounting bolt.. A GM service bulletin identifies a potential for this harness to chafe through, causing shorts or opens on the wires leading directly to the EBCM, which can cause a MIL, no-start conditions, and communication codes.

Real Owner Repair Stories

• Synthesized from multiple forum threads on TahoeYukonForum.com and GM-Trucks.com (2015-2018 Chevrolet Tahoe/Suburban and GMC Yukon/Yukon XL) — Intermittent flickering of dash lights and radio, 'Service StabiliTrak' messages, power steering assist loss when turning at low speeds, and various communication codes.
  ❌ Tried (didn't work) Replacing the battery (sometimes helped temporarily due to full system reset, but problem returned)., Checking fuses., Clearing codes with a basic scanner.
  ✅ What actually fixed it The most commonly reported successful fix was locating and cleaning ground G218. Owners found the dash sound-deadening mat was trapped between the ground eyelet and the body stud. Trimming away the mat, cleaning the contact surfaces of the stud and eyelet with a wire brush or sandpaper, and securely retightening the nut resolved the widespread electrical issues.

Model Year Variations Within This Range

• 2015-2020: The relevant TSBs (PIT5288H, PIT5457D) were updated to include later model years (up to 2019/2020), indicating that the underlying design flaws causing the harness pinching and corrosion issues were not corrected during this generation's production run. Therefore, the diagnosis is consistent across all 2015-2019 models.