OBD-II Code U0104: Lost Communication With Cruise Control Module

What Does U0104 Mean?

The trouble code U0104 means your car's Powertrain Control Module (PCM) lost its connection with the cruise control module. These modules communicate over a network called the Controller Area Network (CAN) bus. When the signal stops for a predetermined amount of time (typically 500 milliseconds), the computer logs this code and disables the cruise control system. On modern vehicles with Adaptive Cruise Control (ACC), this 'module' is usually a front-mounted radar sensor or a forward-facing windshield camera.

Technical definition: The SAE/ISO definition for U0104 is "Lost Communication With Cruise Control Module." This indicates the network communication link between the cruise control module (or driving support ECU/radar sensor) and other control units on the CAN bus has been interrupted.

Can I Drive With U0104?

Yes, But With Caution. You can drive your vehicle, but the cruise control will not work. In 2017-2020 GM models, this code points to a failing gateway module that causes intermittent stalling or a sudden no-start condition. Diagnose the root cause promptly to avoid being stranded.

Common Causes

• Damaged Wiring or Corroded Connectors (Very Common) — Wires in the harness leading to the cruise control module fray, pinch, or break from vibration. Connector pins corrode from moisture and road salt, especially on front-mounted radar sensors, blocking the network signal.
• Faulty Serial Data Gateway Module (GM Vehicles) (Very Common) — On 2017-2020 General Motors vehicles, U0104 is rarely caused by the cruise control module itself. It is triggered by a faulty Serial Data Gateway Module (SDGM) that acts as a network router. When it fails, multiple modules lose communication simultaneously.
• Weak or Failing Battery (Common) — Low battery voltage (below 12.4V) during startup causes widespread communication errors across the vehicle's network. Modules fail to initialize correctly, leading to communication loss codes.
• Loss of Power or Ground (Common) — The cruise control module requires a steady 12-volt power supply and a solid ground connection. A blown fuse, a bad relay, or a corroded chassis ground wire cuts power and forces the module offline.
• Failed Cruise Control Module / Radar / Camera (Less Common) — The module itself fails internally due to water intrusion, electronic component wear, or damage from a minor front-end impact.
• Software Glitch or Corrupted Data (Less Common) — An incomplete software update or data corruption prevents the module from starting up and communicating. A software re-flash by a dealer resolves this.
• Faulty Terminating Resistor (Less Common) — The CAN bus network requires a 120-ohm resistor at each end. If one fails or the wiring breaks, total network resistance changes from 60 ohms to 120 ohms, causing communication to fail.
• Interference from Aftermarket Accessories (Uncommon) — Improperly installed remote starters, alarms, or stereo systems tapped into the wrong wires corrupt CAN bus data signals, forcing modules offline.

Symptoms

• Cruise Control Does Not Work — The cruise control system will not turn on or engage when you press the steering wheel buttons.
• Cruise Control Warning Light is On or Flashing — The dashboard displays a warning light or message for the cruise control or collision avoidance system.
• Check Engine Light is On — The Malfunction Indicator Lamp (MIL) illuminates because the PCM detected a fault in a related system.
• Other Warning Lights (ABS, Traction Control) — Because adaptive cruise control integrates with braking, warning lights for the ABS or traction control systems also illuminate.
• Erratic Electrical Problems — If caused by a faulty gateway module, you experience radio glitches, flickering instrument cluster gauges, or a sudden no-start condition.

Diagnostic Flowchart

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

Common Fixes & Costs

• Repairing Damaged Wiring or Cleaning Connectors — Parts: $5-$50, Labor: $150-$400, ~1.5 hr book time (Intermediate)
• Replacing the Serial Data Gateway Module (GM) — Parts: $70-$150, Labor: $230-$400, ~2.0 hr book time (Professional)
• Reprogramming a Control Module — Parts: $0, Labor: $125-$300, ~1.0 hr book time (Professional)
• Replacing the Cruise Control Module/Radar/Camera — Parts: $300-$1200, Labor: $300-$600, ~3.0 hr book time (Professional)
• Replacing a Blown Fuse or Weak Battery — Parts: $5-$250, Labor: $0-$50, ~0.5 hr book time (DIY)

Used vs. New Parts: Buying Guide

When a used part is worth it: For simple, non-safety-critical modules on older, high-mileage vehicles, a used part from a reputable salvage yard is a cost-effective option. Ensure the part number matches exactly.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the part comes from a vehicle with no flood or heavy front-end damage.
• Match the OEM part number exactly; 'interchangeable' numbers are not reliable for electronic modules.
• Buy from a seller offering at least a 90-day warranty and a clear return policy.

Decision logic:

• If The part is an ADAS safety component (radar, camera). → Buy new OEM. Used sensors have an unknown history, hidden impact damage, and require costly calibration that fails if the part is faulty.
• If The part is a gateway module (e.g., GM SDGM) on a vehicle less than 10 years old. → Favor new OEM or a quality remanufactured unit. Used units have the same inherent flaws as the original failed part.
• If Vehicle is >150K miles and the part is a simple module with no safety function. → A used part is a reasonable risk, but expect a significantly shorter lifespan.

Warranty tradeoff: Used parts typically come with a 30-90 day warranty with no labor coverage. New OEM parts offer warranties of 1 year or longer with potential labor protection.

Worst-case if a used part fails: $300-$1000 if a used module fails after installation, requiring repeat labor costs for diagnosis and replacement.

What Happens If You Wait — Timeline

1. Immediate: Code U0104 is logged as 'active'. The Check Engine Light illuminates and the cruise control system is completely disabled. No other symptoms are present. (MPG impact: 0%% · Added cost: $0)
2. Weeks to Months (If caused by Gateway Module): If the root cause is a failing gateway module, intermittent electrical issues begin. The radio screen goes blank, instrument cluster gauges flicker, or random warning lights appear. (MPG impact: 0%% · Added cost: $0-$500 (Potential cost of misdiagnosing the new, unrelated symptoms))
3. Months (If caused by intermittent wiring/connector issue): A corroding connector or chafing wire worsens. Communication loss becomes frequent, affecting other modules. The vehicle becomes difficult to start on damp days. (MPG impact: 0%% · Added cost: $150 (Cost of a tow if the vehicle fails to start))
4. Long-Term / Sudden Escalation: A failing gateway module or a critical network short causes a sudden no-start or stalling condition while driving, requiring an immediate tow. (MPG impact: N/A% · Added cost: $150 (Tow) + $500-$1500 (Emergency diagnostic and repair of the network failure))

Cost of Not Fixing It

• Immediate: Cruise control system is inoperative. This is a loss of convenience but does not prevent the vehicle from being driven. (Added cost: $0)
• Weeks to Months: On vehicles where U0104 is caused by a failing gateway module, unrelated electrical issues appear, such as radio or instrument cluster glitches. (Added cost: $0-$500 (if other modules are affected or misdiagnosed))
• Long-Term: A failing gateway module or intermittent network short leads to a no-start condition or causes the vehicle to stall while driving. (Added cost: $150-$2000+ (cost of towing plus the critical repair))

Diagnosis Steps

1. Check for Other Trouble Codes
   Use an advanced OBD-II scanner to read codes from all modules. If you see other 'U' codes like U0100, U0101, or U0140, you have a general network problem (faulty gateway module, main bus wiring) rather than an isolated cruise control issue. Address the network codes first.
   Tools: Advanced OBD-II Scanner (Beginner)
2. Inspect Battery Voltage and Fuses
   Use a multimeter to ensure battery voltage is at or above 12.4 volts at rest. Check the fuse box for blown fuses related to the cruise control, ADAS, or gateway modules.
   Tools: Multimeter, Fuse Puller, Owner's Manual (Beginner)
3. Analyze Scan Tool Live Data
   Access the network or gateway module's live data using a bi-directional scan tool. Look for the cruise control module (or 'ACC' / 'Driving Support ECU'). If listed as 'Not Present' or 'Lost Comm', the module is confirmed offline.
   Tools: Advanced Bi-Directional Scan Tool (Advanced)
4. Visually Inspect Wiring and Connectors
   Locate the cruise control module, radar, or camera. Unplug the electrical connector and inspect for green/white corrosion, bent pins, or pushed-out terminals. Follow the wiring harness to check for chafing or damage.
   Tools: Flashlight, Trim Removal Tools (Intermediate)
5. Test for Power and Ground at the Module
   With the ignition on, use a multimeter to verify battery voltage (12V+) at the power pin on the module's connector. Check for continuity to ground on the ground pin (reading less than 1.0 ohm).
   Tools: Multimeter, Vehicle-Specific Wiring Diagram (Intermediate)
6. Check CAN Bus Network Resistance
   With the ignition off and battery disconnected for one minute, measure resistance between CAN High and CAN Low pins at the DLC (pins 6 and 14). A healthy network reads 60 ohms. A reading of 120 ohms indicates an open circuit; 0 ohms indicates a short.
   Tools: Multimeter (Advanced)
7. Check CAN Bus Voltages
   With the ignition on, back-probe the CAN High and CAN Low wires. CAN High fluctuates between 2.5V and 3.5V; CAN Low fluctuates between 1.5V and 2.5V. Stuck voltages indicate a short to ground or power.
   Tools: Multimeter with back-probe pins, Wiring Diagram (Advanced)
8. Isolate the Module
   If the CAN bus is shorted (0 ohms), isolate the faulty component by disconnecting modules one by one. When resistance returns to 60 ohms, the last module disconnected is causing the short.
   Tools: Multimeter, Trim Removal Tools (Professional)
9. Analyze CAN Waveform
   Connect an oscilloscope to CAN High and Low to view the square wave patterns. Distortions or 'ringing' point to physical layer problems like bad termination. A flat line means a major module or gateway failed.
   Tools: Automotive Oscilloscope, Wiring Diagram (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 40-125°F or 180-210°F (Sets during a cold start if a module fails to initialize due to low voltage, or during normal operation when the cruise system is active.)
• RPM: 700-900 or 1500-2500 (Occurs at idle immediately after startup or at a steady cruising RPM when the communication loss happens.)
• Vehicle Speed: 0 mph or >25 mph (Logged at key-on before moving, or once the vehicle reaches a speed where cruise control activation is requested.)
• Battery Voltage: <12.4V or 13.5-14.5V (Low voltage during startup is a primary trigger for communication codes. Occurs with normal charging voltage if a wiring fault exists.)

Related Codes

• U0100 — Lost Communication with ECM/PCM. If U0100 is present with U0104, the problem is a network-wide failure. Check main power/grounds for all modules, the CAN bus wiring, and the gateway module.
• U0101 — Lost Communication with TCM. Since cruise control needs data from the transmission, a TCM communication loss triggers U0104 as a secondary code. Diagnose the U0101 first.
• U0121 — Lost Communication with ABS Control Module. Cruise control relies on wheel speed data from the ABS module. If ABS communication is lost, cruise control is disabled as a safety precaution, setting U0104.
• U0140 — Lost Communication with Body Control Module (BCM). If U0140 appears with U0104, it strongly indicates a bad gateway module or a fault in the main bus wiring.

Climate & Environmental Factors

• High Humidity and Road Salt (Rust Belt): Moisture and salt accelerate corrosion on exposed connectors and wiring, particularly for front-mounted radar sensors located in the grille. This is a leading cause of communication loss.
• Cold Temperatures: Cold starts drop battery voltage significantly, causing modules to fail their initial boot sequence and triggering false U0104 codes.

How to Talk to a Mechanic About This Code

Say this: "I have a U0104 code and I'd like to schedule a diagnostic. I've already checked the battery and related fuses. Can you please start by checking for TSBs and verifying power, ground, and network communication at the cruise control module's connector before recommending a module replacement?"

This signals you've done basic homework and directs the technician toward a logical diagnostic process (wiring and network tests) rather than immediately jumping to replacing an expensive module.

Avoid saying:

• 'My cruise control isn't working, can you fix it?'
• 'My check engine light is on, I think it's the cruise control.'
• 'Just replace the cruise control module.'

Questions to ask before authorizing the repair:

• Did you find other 'U' codes? If so, what does that suggest?
• Were you able to confirm good power and ground at the module connector?
• What was the CAN bus resistance reading? Was it 60 ohms?
• If you are recommending a module replacement, what tests confirmed the old module was bad and not the wiring?
• Does the replacement part require programming or calibration, and is that included in the quote?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended if a known TSB requires a software flash or if an ADAS camera/radar needs replacement and calibration.
  Best for: Vehicles under warranty, recalls, or TSB-related software updates., Complex issues on newer cars requiring proprietary programming or ADAS calibration (e.g., Honda camera, Nissan radar).
  Downsides: Highest labor rates, often 40-50% more than independent shops., Defaults to replacing an entire assembly rather than performing a nuanced wiring repair. (Typical cost: +50% vs. baseline)
• Independent Shop: Excellent fit for most U0104 scenarios, especially for wiring/connector issues. A good independent diagnostician is often better at finding the root cause than a dealer parts-changer.
  Best for: Out-of-warranty vehicles where the cause is likely wiring, a connector, or a known pattern failure (like the GM SDGM)., Owners looking for a better price and a more direct relationship with the technician.
  Downsides: Shop quality and diagnostic equipment vary; ensure they are ASE certified and have experience with network diagnostics., Lacks access to the very latest manufacturer software or calibration tools for brand-new models. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. U0104 is a network communication code that requires advanced diagnostic skills beyond the scope of most chain shops.
  Best for: Simple jobs like battery replacement or fuse changes.
  Downsides: Technicians generally lack the specialized training and equipment for complex network diagnostics., High risk of misdiagnosis, leading to unnecessary and expensive part replacements. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's private-party value, seriously consider selling or trading it in instead of repairing it.

• Car worth $5000, fix is $2100: Borderline. This repair (e.g., a new ADAS camera with calibration) is a significant percentage of the car's value. Get a second opinion before proceeding.
• Car worth $15000, fix is $650: Fix it. This repair (e.g., replacing a GM SDGM) is well below the threshold and restores important functionality.
• Car worth $3000, fix is $1800: Walk away. The repair cost is over 50% of the car's value. It is not a sound financial decision to proceed.

What Scan Tool You Need for This Code

Minimum: A scanner that performs an 'All Module Scan' to see which modules are online and which are not communicating. A basic code reader that only checks the engine is not sufficient.

A cheap code reader only tells you the U0104 code exists. It cannot tell you if other modules are also offline, which is critical information for diagnosing a network problem vs. a single module problem.

Budget: BlueDriver Pro (~$100) — Pairs with your phone and scans all vehicle systems (ABS, SRS, BCM, etc.) to give you a complete list of codes from all modules. This helps determine if the problem is isolated or network-wide.

Mid-range: Innova 5610 / Foxwell NT510 Elite (~$320) — These handheld scanners offer All-Module scanning and live data streaming. Some add bidirectional controls, allowing you to command modules directly to test functionality.

Professional: Autel MaxiCOM MK808S / Launch X431 series (~$450-1200) — Offers full bidirectional control, all-system scanning, and advanced functions like ECU coding and programming. These professional-level tools perform the programming and calibration required after replacing a module.

Rent vs buy: For a one-time U-code diagnosis, buying a midrange or pro scanner is not cost-effective. A budget-friendly 'All Module' scanner like the BlueDriver is a good investment. If the fix requires programming, you need a professional shop regardless of the scanner you own.

How to Clear the Code After You Fix It

1. Reconnect battery if it was disconnected for the repair.
2. Use an OBD-II scan tool to perform the 'Clear DTCs' or 'Erase Codes' function.
3. Perform a complete drive cycle to allow the system's readiness monitors to run.

Drive cycle (~30 minutes): 1) Cold start after the vehicle sits for 8+ hours. 2) Idle for 3 minutes with electrical loads on. 3) Drive for 15 minutes at a steady highway speed (55-60 mph). 4) Perform 15 minutes of mixed stop-and-go driving.

Readiness monitors affected: Comprehensive Component Monitor, CAN Bus System Check

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery clears the code but resets all readiness monitors, causing an automatic emissions test failure.
• If the root cause is not fixed, the U0104 code returns as soon as the module fails its next check-in.
• Some vehicles require a manufacturer-specific drive cycle; a generic one may not set all monitors.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An illuminated Check Engine Light results in an automatic smog test failure. Erasing the code resets readiness monitors, failing the vehicle for being 'Not Ready'.
• New York: Vehicles subject to the NYVIP3 OBD-II inspection fail if the Malfunction Indicator Lamp (Check Engine Light) is on.
• Texas: In the 17 counties requiring emissions testing, an active Check Engine Light is an automatic failure.

Most Commonly Affected Vehicles

• Chevrolet / GMC Silverado, Sierra, Suburban, Yukon, Tahoe (2017-2020) — These vehicles have a known issue where a faulty Serial Data Gateway Module (SDGM) causes U0104. GM TSBs #20-NA-212 and PIT5586G advise reprogramming the SDGM and inspecting the X1/X2 connector terminals before replacement. The updated SDGM part number is 13599318.
• Ford Escape (2017-2019) — TSB 16-0115 was issued for 2017 vehicles built before August 20, 2016, where U0104 appears specifically when using remote start. The fix is a PCM software update performed by a dealer.
• Honda Pilot, Accord (2016-2022) — On models with Honda Sensing, U0104 points to a communication failure with the multi-purpose camera unit. Diagnosis involves checking continuity on the F-CAN lines between the camera and the TCM. Replacement cameras cost over $1,000 and require professional calibration.
• Dodge / Chrysler / Jeep Challenger, 300, Grand Cherokee (2011-2016) — The ABS module sets the code when it stops receiving cruise status messages from the PCM. TSB 18-040-23 Rev. B suggests a PCM software update prevents false detection.
• Subaru Outback, Forester, Crosstrek (2015-2020) — On models equipped with EyeSight, U0104 relates to a communication loss with the stereo camera assembly. Caused by wiring issues, camera misalignment after a windshield replacement, or an internal fault.
• Hyundai / Kia Sonata, Elantra, Optima, Sorento (2016-2023) — For vehicles with Smart Cruise Control (SCC), U0104 points to a communication problem with the front-mounted radar sensor. Common causes include damage from a minor front-end impact or a dirty sensor.
• Nissan Rogue, Altima, Maxima (2016-2021) — On Nissans with Intelligent Cruise Control (ICC), U0104 accompanies codes like C1A16. The cause is frequently a dirty or misaligned front radar sensor. TSB NTB19-033G addresses this issue.

Manufacturer-Specific Notes

• General Motors (Chevy/GMC): Code U0104 is frequently caused by a faulty Serial Data Gateway Module (SDGM), not the cruise control components. TSBs #20-NA-212 and #PIT5586G detail this issue.
• Ford: On 2017 Escapes with adaptive cruise, a software glitch causes U0104 to set specifically when using the remote start feature. TSB 16-0115 advises a PCM software update.
• Honda: For models with Honda Sensing, the 'cruise control module' is the multi-purpose camera unit. Diagnosis involves checking the F-CAN communication lines between this camera and the TCM.
• Toyota: On systems with Dynamic Radar Cruise Control, U0104 is stored by the network gateway ECU when communication with the 'driving support ECU' is lost.
• Dodge / Chrysler / Jeep: TSB 18-040-23 Rev. B indicates a PCM software update is available to prevent the false detection of code U0104-00 by the ABS module.

Real Owner Stories

2018 Chevy Silverado - Easy Fix

Owner reported the cruise control stopped working alongside multiple warning lights, including 'Service Power Steering'. The radio display acted erratically. Codes U0104, U0140, and others were present.

Outcome: The main X1 connector on the SDGM was slightly loose. After unplugging it, inspecting the pins, and firmly plugging it back in until it clicked, all communication codes cleared. The fix required no parts and 20 minutes of labor.

Lesson: On 2017-2020 GM trucks, a flood of 'U' codes is frequently caused by a poor connection at the SDGM. Always check SDGM connectors before replacing parts.

2019 Honda Pilot - Misdiagnosis Story

At 54,000 miles, the dash displayed 'Adaptive Cruise Control Problem' and 'Lane Keeping Assist Problem'. The dealer scanned code U0104.

Outcome: The owner sought a second opinion. An independent shop performed a detailed wiring check and found a high-resistance point in the F-CAN wiring between the camera and the TCM. A $300 wiring repair fixed the problem completely.

Lesson: U0104 indicates a communication loss, not necessarily a failed module. Insist on a full diagnosis of the wiring, power, and ground circuits before replacing an expensive ADAS camera.

2017 Ford Escape - Unusual Root Cause

The Check Engine Light illuminated with code U0104 only after using the remote start feature. If started normally with the key, the cruise control worked fine.

Outcome: The owner found Ford TSB 16-0115, describing this exact scenario for 2017 Escapes built before August 20, 2016. The dealer performed a PCM software update, resolving the issue permanently for one hour of labor.

Lesson: Always check for TSBs related to your specific vehicle. A seemingly complex hardware problem is often a known software bug with a simple reprogramming fix.

How to Prevent This Code From Triggering

• Apply Dielectric Grease to Exposed Connectors (During any related service) — Applying non-conductive dielectric grease to connector seals creates a barrier that repels moisture and road salt, preventing pin corrosion.
• Maintain Battery Health and Connections (Annually) — A weak battery providing low voltage during startup is a primary cause of random communication codes. Test batteries over 3 years old and keep terminals clean.
• Keep Radar/Camera Sensors Clean (As needed) — A buildup of dirt, snow, or ice on the front grille emblem or windshield obstructs the sensor's view, causing it to shut down and post communication codes.
• Secure Wiring Harnesses (During routine maintenance) — Visually inspect wiring harnesses to ensure they are properly clipped in place and not rubbing against sharp edges, preventing wires from chafing and shorting the CAN bus.
• Wash the Vehicle's Undercarriage (Seasonally) — Washing away road salt and grime prevents corrosion of critical ground points, wiring harnesses, and module connectors exposed to the elements.

Frequently Asked Questions

Can I still drive my car with a U0104 code?

Yes, but your cruise control will not function. Because this code often signals a larger network problem, diagnose it promptly to prevent other systems from failing unexpectedly. Ignoring it risks a sudden no-start condition.

Will the U0104 code clear itself?

If the communication loss was a temporary glitch caused by low battery voltage during startup, the code moves to 'history' status and the cruise control resumes functioning. However, an 'active' code that returns immediately indicates a persistent hardware or software problem requiring repair.

How much does it cost to fix a U0104 code?

Costs range from $20 for a simple fuse replacement to $150-$450 for wiring repairs. Replacing a faulty gateway module (common on GM vehicles) costs $300-$550, while replacing a modern radar or camera unit exceeds $1,000 due to mandatory calibration.

What is the most common misdiagnosis for U0104?

The most common mistake is immediately replacing the expensive cruise control module or radar sensor without testing the network. Technicians frequently find the true cause is a corroded connector, a blown fuse, or a completely different module like the Serial Data Gateway Module.

Can a bad battery cause a U0104 code?

Yes. A weak battery providing under 12.4 volts during startup causes multiple modules to fail their initial communication check-in. This results in a flood of 'U' codes, making battery testing the mandatory first step in diagnosis.

My cruise control uses radar. Is the U0104 code related to that?

Yes. On vehicles with Adaptive Cruise Control, the front radar sensor or windshield camera acts as the cruise control module. A U0104 code means the main computer lost communication with this specific ADAS unit, disabling collision avoidance features.

Can a bad ground cause code U0104?

Yes. A loose or corroded ground wire prevents the cruise control module from powering on and communicating. Furthermore, a bad common ground point shared by multiple modules causes a variety of communication codes to appear simultaneously.

Key Takeaways

• Code U0104 indicates the Powertrain Control Module (PCM) lost network communication with the cruise control module or forward-facing ADAS camera.
• Always test the battery and inspect wiring first; voltage drops below 12.4V or corroded pins cause 80% of these communication failures.
• On 2017-2020 GM trucks and SUVs, a faulty Serial Data Gateway Module (SDGM) is the primary culprit, often requiring a $300-$550 replacement and reprogramming.
• You can safely drive with this code, but ignoring it risks a sudden no-start condition if the underlying fault is a failing network gateway module.