U0028 on 2015-2018 Chevrolet Colorado: Infotainment Network Fault Causes & Fixes

What's Unique About the 2015-2018 Chevrolet COLORADO

The 2015-2018 Colorado and its twin, the GMC Canyon, rely on this MOST network for all infotainment functions. Unlike some larger GM trucks where a pinched wiring harness is the most common culprit, on the Colorado, the issue is more frequently an internal failure of one of the modules on the network ring, such as the HMI module or the radio itself. The provided NHTSA Technical Service Bulletin (TSB) #PIC6073E specifically directs technicians to diagnose the MOST bus when this code appears, confirming its direct link to the infotainment system. Another TSB, #PI1149A, further details the diagnostic process, noting that a blank screen with no audio at startup is a key indicator of a MOST bus failure.

Diagnostic Flowchart

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

Symptoms You May Notice

• Black or blank infotainment screen
• No sound from the audio system
• Radio controls (on the dash and steering wheel) are non-functional
• Loss of audible chimes for turn signals or warnings
• Backup camera does not display
• Dead battery after the vehicle sits for a period (parasitic drain)

Most Likely Causes

1. Failed Human Machine Interface (HMI) Module 🔴 High Probability The HMI module is the 'brain' of the infotainment system and a central node in the MOST network. Its internal failure is a very common cause for breaking the communication ring on this platform.
   How to confirm: A technician will use a MOST bypass loop to take the HMI module out of the network ring. If communication is restored to other modules (e.g., audio returns), the HMI module is faulty. The HMI is located behind the glove box. 🎬 Watch: How to access and replace the HMI module
   Typical fix: Replace the HMI module. This part must be programmed to the vehicle's VIN after installation. Specialists can provide pre-programmed modules to avoid a dealer visit.
   Est. part cost: $250-$550
2. Failed Radio/Tuner Module 🟡 Medium Probability The radio module is the 'master' of the MOST bus and generates the network clock. An internal electronic failure can cause it to stop communicating, which brings down the entire network.
   How to confirm: Using a MOST bypass loop, a technician will bypass other modules first. If the fault persists, the radio is a likely cause. The bypass kit does not include a loop for the radio itself, as it's the master. Other modules may store a U0184 'Lost Communication With Radio' code.
   Typical fix: Replace the radio/tuner module. This part is located in the center dash stack and requires VIN programming.
   Est. part cost: $200-$600
3. Failed CD/Media Player 🟡 Medium Probability Even if never used, the CD player is an active node in the MOST communication ring. Its internal failure will break the circuit and cause a U0028 code. A technician on the iATN forum identified the CD player as the cause in a similar GM truck.
   How to confirm: This is often an easy module to test. A technician can bypass the CD player with a loop tool. If the screen and radio function return, the CD player is faulty.
   Typical fix: Replace the CD player or, more commonly, permanently install a MOST bypass loop to eliminate it from the network if CD playback is not needed.
   Est. part cost: $150-$350
4. Wiring or Connector Issue ⚪ Low Probability While less common on the Colorado than on larger GM trucks, the MOST bus wiring can still be damaged or have loose connections behind the dash, particularly at the connectors for the HMI or radio modules.
   How to confirm: Visually inspect the wiring and connectors at the back of the HMI module (behind glove box) and radio module (in center stack) for any signs of damage, corrosion, or loose pins.
   Typical fix: Repair the damaged section of the wiring harness or clean/reseat the connector.
   Est. part cost: $10-$50

Rare But Worth Checking

• Failed Instrument Panel Cluster (IPC): The IPC is also a node on the MOST bus. While a rare failure point for this specific code, an internal fault in the cluster can bring down the network. This would be diagnosed using the same bypass loop procedure on the other modules; if they all check out, the IPC becomes a suspect.
• Software Glitch: Occasionally, a software anomaly can cause communication issues. A 'hard reset' by disconnecting the battery for 15 minutes may resolve a temporary glitch. A dealer can also check if any infotainment software updates are available, as mentioned in TSBs like PI1149A for related issues.

Diagnosis Steps

1. Perform a full vehicle DTC scan to see which modules are logging U0028 or other communication codes.
2. Confirm the primary symptoms: blank screen and no audio at startup.
3. Access the MOST bus modules. The HMI module is behind the glove box, and the radio/CD player is in the center dash stack.
🎬 Watch: Troubleshooting a Colorado radio that won't turn on
4. Visually inspect connectors and nearby wiring for obvious damage or loose connections.
5. Using a MOST bypass loop tool (e.g., GM EL-51578), start by bypassing the most accessible module (often the CD player or HMI module).
6. After bypassing a module, cycle the ignition. If infotainment functions return, the bypassed module is the one that has failed.
7. If the first module is not the cause, reconnect it and move the bypass loop to the next module in the ring. The typical ring order is Radio -> CD Player -> HMI -> Instrument Cluster -> Radio.
8. Once the faulty module is identified, verify it has proper power and ground before condemning it.

Parts You'll Likely Need

• Human Machine Interface (HMI) Module (OEM #84156701, 84028492, 84543381 (Verify by VIN and RPO code IO5/IO6)) — This is the central computer for the infotainment system and a very common failure point that breaks the MOST communication ring.
  Trusted brands: ACDelco
  OEM price range: $300-$550
  Aftermarket price range: $250-$450 (often pre-programmed)
• Radio / Tuner Module (OEM #23402905 (Verify by VIN)) — As the master of the MOST bus, an internal failure in the radio will take down the entire network, causing a U0028 code.
  Trusted brands: ACDelco
  OEM price range: $300-$600
  Aftermarket price range: $250-$450
• MOST Bus Bypass Loop (OEM #EL-51578) — This is an essential diagnostic tool for isolating the failed module. It can also be used as a permanent, low-cost fix to bypass a non-essential failed module like a CD player.
  OEM price range: $20-$50
  Aftermarket price range: $10-$30

Related Codes That Often Appear With This One

• U0029 — This code also indicates a MOST bus performance issue. U0028 often means the network is completely off (a 'ring break'), while U0029 can mean the ring is intact but a module is not communicating correctly. They frequently appear together.
• U0184 — This code means 'Lost Communication With Radio'. If the radio module itself fails, other modules on the network will log this code, pointing directly to the radio as the likely culprit.

Technical Service Bulletins (TSBs) & Recalls

• PIC6073E — Diagnostic Tip: EL-51578 MOST Bus Diagnostic Tool Kit — This bulletin explicitly links U0028 to MOST bus failures like a blank radio display and inoperative controls. It instructs technicians to use the EL-51578 bypass loop tool kit to diagnose the ring and find the faulty module.
• PI1149A — Intermittent Radio Blank Display With or Without Audio and MOST BUS Diagnostic Aid — This bulletin provides detailed diagnostic advice for U0028/U0029. It clarifies that a blank screen with no audio at startup is the classic symptom of a MOST bus failure. It also provides diagnostic clues based on whether the failure occurs at startup or while driving.

Platform-Specific Known Issues

• TSB #PIC6073E directly links DTC U0028 to the Media Oriented Systems Transport (MOST) bus, instructing technicians to use the EL-51578 diagnostic tool kit to bypass modules and find the source of the ring break.
• TSB #PI1149A provides further diagnostic context, confirming that a blank screen and no audio upon vehicle startup is the classic symptom of a MOST bus that is down, which is the condition that sets code U0028.

Mechanic-Grade Diagnostic Values

• Module Power and Ground Verification — expected: Battery voltage (12.0-14.5V) at the power pin and less than 0.1 ohms resistance to ground.. Failure: No voltage, low voltage, or high resistance on the ground circuit will prevent a module from powering on, causing a ring break.
• MOST Control Circuit Voltage (ECL) — expected: A specific voltage reading on the ECL terminal, which can be verified using the EL-51578 bypass tool.. Failure: An incorrect voltage indicates a fault in the bus control circuit.

Hidden / Shadow Codes Worth Checking

• U0029 (in conjunction with U0028): While U0028 indicates a complete ring break ('Bus Off'), U0029 can indicate a performance issue where the ring has integrity but a module is not communicating correctly. Seeing U0029 with a 'Number of MOST Communication Breaks = 0' in scan data strongly suggests an internal module fault, not a wiring break. (see via GM GDS2 (Global Diagnostic System 2) or an equivalent high-end scan tool, viewing data from the Radio (A11) and HMI modules.)

Scan Tool Commands That Help

• GDS2 (Data Bus Diagnostic Tool function): View 'Surrogate MOST Master Node Upstream Position' PID — This is the most critical diagnostic step. This data PID in the radio module will display a number (e.g., '2'). This number indicates the position of the last healthy module in the ring before the break. By knowing the ring order (Radio -> CD -> HMI -> IPC), a technician can count backwards to pinpoint the failed module or the wiring section immediately after the indicated module.
• GDS2: Module Programming/Setup — After replacing an HMI or Radio module, the new module must be programmed to the vehicle's VIN and configured for its specific RPO codes (IO5/IO6). This function is required to make the new part work.

Wiring & Ground Locations

• HMI Module Connector (Gray 12-pin) — Behind the glove box, plugged into the HMI module.. This connector provides power, ground, and video signals. The backup camera video signal wires are located at Pin 5 (Gray/Yellow) and Pin 6 (White/Blue). While not directly the MOST bus, checking for secure connection and no damage here is a key step.
• Radio/Tuner Module Connectors — In the center dash stack, behind the infotainment screen/controls.. The Radio is the master of the MOST bus. All power, ground, and MOST bus connections must be secure for the network to initialize. A fault here will bring down the entire system.

Real Owner Repair Stories

• iATN (International Automotive Technicians Network) Forum (2015 Chevrolet Silverado (same MOST infotainment platform)) — MyLink display was dark, radio would not play, and all control buttons were non-functional.
  ❌ Tried (didn't work) The technician specifically avoided random part swapping and focused on data-driven diagnosis.
  ✅ What actually fixed it The technician used a GDS2 scan tool and found U0028 in the radio and U0029 in the HMI. The key was the 'Surrogate MOST Master Node Upstream Position' PID, which read '2'. Knowing the ring order was Radio(1)->CD(2)->HMI(3)->IPC(4), they determined the break was after the CD player. They used a MOST bypass loop on the CD player, and the system came back to life. The final fix was replacing the failed CD player module.

OEM Part Supersession History

• 84156701 (HMI Module) → 84296482 — Part revision or update by the manufacturer.
  Heads up: Ensure the replacement part is correct for the vehicle's HMI generation (2.0 for 2015, 2.5 for 2016-2018).

Model Year Variations Within This Range

• 2015 only: These models use the HMI 2.0 system. It has a dual-core processor and does NOT support Apple CarPlay or Android Auto. Replacement parts must be HMI 2.0 compatible.
• 2016-2018: These models use the HMI 2.5 system. It features a faster quad-core processor and supports wired Apple CarPlay and Android Auto. Replacement parts must be HMI 2.5 compatible.
• All: Upgrading a 2015 model from HMI 2.0 to 2.5 is possible but requires replacing the HMI module, the Radio/Tuner module, and the USB hub assembly simultaneously. The modules are not directly interchangeable.