U0164 on 2017-2019 Chevrolet Silverado 2500: HVAC Communication Loss Fixes

What's Unique About the 2017-2019 Chevrolet SILVERADO 2500

For the 2017-2019 Silverado 2500 and its platform mates, many communication codes, including U0164, are often traced back to a central hub called the Serial Data Gateway Module (SDGM), designated K56. Manufacturer bulletins specifically point to issues with this module's connectors or internal logic, which can cause a flood of communication errors with various components, not just the HVAC system. This makes the SDGM a primary suspect, whereas on other vehicles, the focus might be solely on the HVAC module itself. The SDGM acts as a bridge between different vehicle networks, and a fault there can isolate multiple modules simultaneously.

Diagnostic Flowchart

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

Symptoms You May Notice

• Climate control panel is unresponsive or inoperative.
• Inability to change fan speed, temperature, or airflow direction.
• A/C system may not engage.
• HVAC system may default to a single setting, like defrost.
• Warning messages on the instrument cluster or infotainment screen, such as "Climate Off".
• HVAC display on the radio is blank or shows incorrect information.
• Audible chimes for turn signals or warnings may be absent if the issue stems from the SDGM.

Most Likely Causes

1. Poor Connection or Logic Lock at Serial Data Gateway Module (SDGM) 🔴 High Probability As identified in GM Technical Service Bulletins PIT5586E and PIT5586, the SDGM connectors (X1 and X2) are a known point of failure. Terminals can become bent, backed out, or suffer from poor tension, causing a host of communication DTCs. The module can also experience a 'logic lock' state that requires a reset.
   How to confirm: A technician will inspect the X1 and X2 connectors at the SDGM for loose, spread, or corroded terminals. A full system scan will likely show multiple 'U' codes (e.g., U0100, U0140, U0155), pointing to a gateway issue rather than a single module failure. The SDGM is typically located behind the driver's side lower dashboard panel.
   Typical fix: Repairing the terminals in the SDGM connectors is the first step. This may involve re-seating or replacing individual pins. For 'logic lock', a hard reset (disconnecting the battery for several minutes) or pulling the SDGM fuse may work. In some cases, the SDGM requires reprogramming or replacement.
   Est. part cost: $0-$50 for terminal repair, $150-$300 for a replacement SDGM.
2. Faulty HVAC Control Module 🟡 Medium Probability Like any electronic component, the HVAC module (K33) can fail internally. This can be due to component failure on the circuit board or software corruption.
   How to confirm: If the SDGM and wiring are confirmed to be good, a technician will use a scan tool to attempt direct communication with the HVAC module. If the module does not respond despite having good power and ground at its connector, it has likely failed internally.
   Typical fix: Replacement and reprogramming of the HVAC control module. The new module may need to go through an 'actuator learn' procedure with a scan tool.
   Est. part cost: $200-$450
3. Blown Fuse or Poor Ground ⚪ Low Probability
   How to confirm: Check the fuses related to the HVAC system, Body Control Module (BCM), and Infotainment system in the fuse panels (instrument panel and underhood). Verify that the HVAC module and SDGM are receiving proper power and have a solid ground connection using a multimeter. Poor engine block grounds have been known to cause random electrical issues on GM trucks.
   Typical fix: Replace the blown fuse or clean and secure the ground connection.
   Est. part cost: $1-$20
4. Wiring Harness Damage or Corrosion ⚪ Low Probability
   How to confirm: Visually inspect the wiring and connectors going to the HVAC control module (behind glove box) and the SDGM (driver's side dash). Check for signs of chafing, breaks, or water intrusion. A multimeter can be used to check for continuity and shorts in the CAN bus wires (typically checking for ~60 ohms of resistance across the bus with the battery disconnected).
   Typical fix: Repairing the damaged section of the wire or cleaning/replacing the corroded connector.
   Est. part cost: $10-$100

Rare But Worth Checking

• Software Anomaly between Radio and HVAC:

Diagnosis Steps

1. Perform a full vehicle scan to check for other 'U' (communication) codes. The presence of multiple U-codes strongly points towards a network or gateway problem.
2. Refer to TSBs #PIT5586E and #PIT5586B. Locate the Serial Data Gateway Module (SDGM) behind the driver's side lower dash.
3. Disconnect the battery. Carefully inspect the SDGM's X1 and X2 connectors for any signs of bent pins, backed-out terminals, corrosion, or damage. Pay close attention to terminal tension. Repair as needed.
4. If connectors look good, check for power and ground at the HVAC control module connector (behind the glove box) using a multimeter.
5. Check the fuses for the HVAC system, BCM, and SDGM in the instrument panel and underhood fuse blocks.
6. If power and ground are good, inspect the CAN bus wiring between the HVAC module and the SDGM for opens or shorts. Resistance between the two CAN lines should be approximately 60 ohms.
7. If all wiring and connections are confirmed good, the issue likely lies with either the HVAC control module or the SDGM itself. Professional diagnosis with an advanced scan tool is required to isolate the faulty module.
8. A temporary 'logic lock' can sometimes be cleared by disconnecting the battery for 30 minutes or pulling the SDGM fuse for a minute.

Parts You'll Likely Need

• Serial Data Gateway Module (OEM #13599318) — This module is a known failure point according to GM TSBs, causing widespread communication issues, including U0164. It is often the root cause when multiple 'U' codes are present.
  Trusted brands: ACDelco, Genuine GM
  OEM price range: $200-$300
  Aftermarket price range: $150-$250
• HVAC Control Module — If the gateway module and wiring are good, the HVAC module itself may have failed internally, preventing it from communicating on the network.
  Trusted brands: ACDelco
  OEM price range: $300-$450
  Aftermarket price range: $200-$350
• Connector Terminal Pins — The most common fix per TSBs is repairing terminals in the SDGM connectors, not replacing the whole module.
  Trusted brands: ACDelco
  OEM price range: $5-$15 per terminal

Related Codes That Often Appear With This One

• U0100 — Lost Communication with ECM/PCM
• U0101 — Lost Communication with TCM
• U0140 — Lost Communication with Body Control Module
• U0155 — Lost Communication with Instrument Panel Cluster (IPC) Control Module
• U0184 — Lost Communication With Radio

Technical Service Bulletins (TSBs) & Recalls

• PIT5586E: Mentions U0164 as part of a group of DTCs caused by a logic lock or connector issues at the Serial Data Gateway Module.
• PIT5586B: Specifically calls out checking the Serial Data Gateway Module X2 connector for terminal problems when U0164 and other codes are present.
• PIT5586: The original TSB identifying the root cause as bent, backed-out, or loose terminals in the SDGM X1 or X2 connectors.
• 19-NA-189: Addresses software anomalies causing 'Climate Off' messages on the radio, requiring reprogramming of the SDGM and/or radio.

Platform-Specific Known Issues

• A 'logic lock' condition in the Serial Data Gateway Module can occur, requiring a reset (fuse pull or battery disconnect) or reprogramming to restore communication. (Source: TSB #PIT5586E).
• Terminal issues (bent, loose, backed-out) in the X1 and X2 connectors of the Serial Data Gateway Module are a common cause of this and other communication codes. (Source: TSB #PIT5586B).

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Network Resistance — expected: Approximately 60 Ω between Pin 6 (CAN_H) and Pin 14 (CAN_L) at the DLC with the battery disconnected.. Failure: A reading of ~120 Ω indicates an open circuit or a missing terminating resistor. A reading of 0 Ω indicates a direct short between the two CAN lines.
• High-Speed CAN Bus Voltage (Key On, Engine Off) — expected: CAN_H and CAN_L should both be approximately 2.5V at rest. During data transmission, CAN_H should toggle towards 3.5V and CAN_L towards 1.5V.. Failure: Voltages that are stuck high, low, or are identical may indicate a short between the wires, or a short to power/ground.
• HVAC Control Module (K33) Power Supply — expected: 11 to 14 V at Pin 1 (RD/WH wire) of the module connector with the ignition ON.. Failure: Low or no voltage indicates a problem with the fuse or power supply wiring.
• HVAC Control Module (K33) Ground Resistance — expected: Less than 0.1 Ω between Pin 7 (BK wire) of the module connector and a clean chassis ground.. Failure: Higher resistance indicates a poor ground connection, which can cause the module to malfunction or drop off the network.

Hidden / Shadow Codes Worth Checking

• DTC with Symptom Byte (e.g., U0164 71): GM uses a two-digit hexadecimal 'symptom byte' to add detail to U-codes. For example, a '71' indicates 'Invalid Data Received', meaning the module setting the code is getting bad information from the source module (in this case, the HVAC module), pointing to the HVAC module or its inputs as the fault. (see via A dealer-level scan tool like the GM GDS2 (Global Diagnostic System 2) is required to view symptom bytes.)

Scan Tool Commands That Help

• GM GDS2: Module Diagnostics > Control Functions — To perform bidirectional tests on the HVAC module. A technician can command functions like changing fan speed or mode door position. If the module does not respond, it helps confirm a communication or internal module fault.
• GM GDS2 with SPS (Service Programming System): Serial Data Gateway Module Reprogramming — This is a primary corrective action outlined in GM TSBs for a suspected SDGM 'logic lock' or software error that causes widespread communication loss, including code U0164.
• GM GDS2: HVAC Control Module > Control Functions > Actuator Learn — After replacing the HVAC control module, this procedure is required to calibrate the new module and teach it the position of the blend door actuators.

Wiring & Ground Locations

• K33 HVAC Control Module — Located behind the glove box. Pin 1 (RD/WH) is battery power, and Pin 7 (BK) is the ground.. This is the module that has lost communication. Verifying power and ground directly at its connector is a critical diagnostic step.
• K56 Serial Data Gateway Module — Located behind the driver's side lower dashboard panel, near the steering column. [Pass 2]. This is the central communication hub and a known failure point according to TSBs. Its connectors, X1 and X2, are primary inspection points.
• G218 — A key ground point for the Body Control Module (BCM). While exact location can vary, instrument panel grounds are often located behind the driver or passenger kick panels.. GM TSB #18-NA-358 identifies a poor BCM ground at G218 as a potential cause for various communication codes. A bad ground here can disrupt the entire network.
• Engine Harness Chafe Points — Common chafe points include the corner of the left cylinder head, the drive belt idler pulley bracket, the ECM/TCM bracket, the driver-side upper control arm, and the shock tower bolt.. Damage at these points can short various circuits in the engine harness, leading to a wide range of unpredictable electrical faults, including network communication codes.

Real Owner Repair Stories

• Advanced Level Diagnostics YouTube Channel (2018 Chevrolet Silverado (K2XX Platform)) — Multiple communication codes present, airbag light on, and a blank radio screen.
  ❌ Tried (didn't work) The reporting shop suspected a major network issue and stopped diagnosis, fearing a complex and expensive repair.
  ✅ What actually fixed it The technician identified and replaced a single blown 10-amp fuse in the instrument panel fuse block on the right (passenger) side of the dashboard. This fuse powered one of the modules that had dropped off the network, causing the cascade of communication codes.

When the Usual Fixes Don't Work

• While the TSBs heavily point to the Serial Data Gateway Module (SDGM) as the primary cause, there are documented cases where the root cause was much simpler. In one instance on a 2018 Silverado with multiple communication codes, the final repair was a single blown 10-amp fuse for a different module on the network. This highlights the importance of checking all basic power and ground inputs for all modules before focusing solely on the SDGM or assuming a complex network failure.

OEM Part Supersession History

• 13509768, 13524297, 13524298, 13599317 → 13599318 — Standard part evolution for bug fixes, hardware revisions, or supplier changes.
  Heads up: Part 13599318 is the current service replacement for the earlier numbers on this platform. Always verify fitment with VIN, as programming is required.

Model Year Variations Within This Range

• 2017-2019: The underlying cause of U0164 (SDGM logic lock or connector issues) remains consistent across these model years. However, the specific Technical Service Bulletin (TSB) number to reference may have changed. For example, the PIT5586 series was later updated and superseded by bulletins like 20-NA-212, which provided refined diagnostic or software programming instructions. The physical parts and failure mode are the same.