U0104 — Lost Communication With Cruise Control Module #

DTC U0104 means that a control module expected communication from the cruise-control-related module but did not receive the required network messages.

This is a communication fault. It does not automatically mean the cruise control module itself has failed.

Depending on the vehicle architecture, the function identified as the “Cruise Control Module” may be a dedicated module, an adaptive cruise radar unit, a front camera, an ADAS controller or another module responsible for cruise-control data.

Diagnosis should therefore begin by identifying which module stored U0104, which module is missing from the network, and whether the fault is current or historical.

What Does U0104 Mean? #

Modern vehicles exchange information between control modules over one or more data networks, commonly CAN-based networks.

Each module expects specific messages from other modules. If an expected cruise-control-related module stops transmitting, or if another controller cannot receive its messages for the calibrated period of time, U0104 can be stored.

The standardized description is commonly:

Lost Communication With Cruise Control Module.

However, the physical module associated with that description is vehicle-specific.

U0104 Does Not Automatically Mean the Cruise Module Is Bad #

A module can disappear from the network for many reasons other than internal failure.

For example:

• the module may have lost battery power;
• its ignition supply may be missing;
• its ground may have excessive resistance;
• a fuse may be open;
• a connector may be disconnected or corroded;
• CAN wiring may be open or shorted;
• another network fault may prevent communication;
• low vehicle voltage may have caused a temporary reset;
• a software or calibration issue may create an intermittent communication fault;
• the module itself may have failed.

Module replacement should come after the external power, ground, wiring, network and software possibilities have been checked.

Which Module Does U0104 Refer To? #

Do not assume that every vehicle has a separate box labeled “Cruise Control Module.”

Depending on manufacturer and equipment, cruise-control functions may be integrated into:

• a radar sensor;
• a front camera;
• an adaptive cruise control module;
• a driver-assistance control module;
• a powertrain controller;
• another manufacturer-specific electronic unit.

The vehicle wiring diagram and module topology should be used to identify the actual controller associated with U0104.

Common Symptoms of U0104 #

Symptoms depend on the vehicle and on whether the communication failure is current or only stored as history.

• cruise control unavailable;
• adaptive cruise control unavailable;
• cruise control will not engage;
• cruise control cancels unexpectedly;
• driver-assistance warning message;
• check-engine or service warning lamp on some applications;
• additional communication DTCs;
• module shown as offline or unavailable on a full-system scan;
• other ADAS features unavailable if they share the same module;
• in some cases, no current symptom.

A stored U0104 after a temporary low-voltage or software event may not indicate an active hardware failure.

Possible Causes of U0104 #

Possible causes include:

• missing power supply to the cruise-control-related module;
• poor module ground;
• blown fuse or fusible link;
• damaged module connector;
• water intrusion or corrosion;
• open CAN High or CAN Low circuit;
• short between CAN circuits;
• CAN circuit shorted to ground or voltage;
• network gateway problem;
• low 12V system voltage;
• module reset during cranking;
• aftermarket equipment connected to the vehicle network;
• incorrect configuration or programming;
• manufacturer-specific software/calibration issue;
• internal failure of the affected module.

How to Diagnose U0104 #

1. Perform a Full Vehicle Scan #

Do not look only at the engine ECU.

Record:

• every stored and pending DTC;
• which module stored U0104;
• whether U0104 is current, intermittent or history;
• which modules respond to the scan tool;
• other U-series communication codes;
• battery-voltage or power-supply codes.

If many modules report that the same controller is missing, the problem may genuinely involve that controller, its power supply or its network connection.

If only one module reports U0104 while all other modules communicate normally with the cruise-control-related controller, the diagnostic direction may be different.

2. Check Whether the Target Module Communicates #

Use a scan tool capable of accessing the relevant vehicle networks.

Try to communicate directly with the module associated with cruise control.

If the module responds normally, U0104 may be:

• an intermittent fault;
• a historical low-voltage event;
• a temporary network interruption;
• a software or timing-related communication problem.

If the module does not respond, continue with power, ground and network diagnosis.

3. Identify the Vehicle Network Architecture #

Obtain the wiring diagram and network topology for the exact vehicle.

Determine:

• which module corresponds to U0104;
• which network it uses;
• whether communication passes through a gateway;
• which fuses supply the module;
• which grounds serve the module;
• which network splice or connectors are involved.

This step is especially important on vehicles with several CAN networks linked through a central gateway.

4. Check Battery and System Voltage #

Low system voltage can cause electronic modules to reset or temporarily stop communicating.

If U0104 appeared after:

• a flat battery;
• jump starting;
• extended cranking;
• battery replacement;
• charging-system trouble;

check the 12V battery and charging system before replacing network components.

If voltage-related codes such as U3003 are also present, diagnose the electrical supply problem first.

5. Check Module Fuses and Power Supplies #

A module with no electrical power cannot communicate.

Use the wiring diagram to identify every supply circuit to the affected module.

Check:

• constant battery supply;
• ignition-switched supply;
• relevant fuses;
• relays where fitted;
• high-current distribution circuits where applicable.

Do not rely only on visual inspection of a fuse. Verify the circuit electrically and preferably under load when appropriate.

6. Check Module Grounds #

A ground connection can appear electrically continuous with a multimeter but still develop excessive voltage drop when the module is operating.

Inspect:

• ground terminals;
• body grounds;
• corrosion;
• loose fasteners;
• damaged ground wiring.

Perform voltage-drop testing according to the manufacturer procedure where required.

7. Inspect the Module Connector #

Disconnect connectors only according to manufacturer safety procedures.

Inspect for:

• water intrusion;
• green or white corrosion;
• bent pins;
• pushed-back terminals;
• poor pin tension;
• damaged connector locks;
• harness tension;
• evidence of previous repairs.

Radar and front-camera modules may be exposed to areas where moisture, collision repairs or body work can affect connectors and wiring.

8. Check the Data Network #

If module power and grounds are correct but communication is still absent, investigate the network circuits.

Possible faults include:

• open CAN High;
• open CAN Low;
• short between network wires;
• short to ground;
• short to battery voltage;
• poor splice connection;
• gateway or connector fault.

Use the manufacturer wiring diagram and diagnostic procedure.

9. Do Not Treat “60 Ohms” as a Universal CAN Test #

Approximately 60 ohms is often expected across a conventional high-speed CAN network using two 120-ohm terminating resistors when the network is powered down and isolated appropriately.

However, modern vehicles may use:

• multiple CAN buses;
• gateways;
• branch networks;
• different termination strategies;
• CAN FD networks;
• manufacturer-specific network layouts.

Therefore, measuring resistance at the diagnostic connector and expecting exactly 60 ohms is not a universal pass/fail test for U0104.

Use the vehicle-specific network specification.

10. Check Related Communication Codes #

Other codes can reveal whether the problem is isolated or part of a larger network event.

• U0405 — Invalid Data Received From Cruise Control Module
• U0100 — Lost Communication With ECM/PCM
• U0121 — Lost Communication With ABS Control Module
• U0140 — Lost Communication With Body Control Module
• U3003 — Battery Voltage

If several modules disappear from the network at the same time, investigate shared power, grounds, gateway circuits and common network wiring before focusing only on the cruise-control-related module.

11. Check for Manufacturer Software Updates #

U0104 can sometimes be set by a software or calibration issue rather than a permanent wiring or module failure.

Before replacing an expensive control module, check:

• manufacturer technical service bulletins;
• known software updates;
• module calibration level;
• programming requirements;
• vehicle-specific diagnostic instructions.

Software should not be assumed to be the cause on every vehicle, but documented manufacturer cases show that it can be relevant.

12. Consider Module Failure Only After External Checks #

If the module has:

• correct power;
• correct grounds;
• intact network wiring;
• correct configuration;
• no applicable software issue;

but still does not communicate, internal module failure becomes more plausible.

Follow the manufacturer diagnostic procedure before replacement.

A replacement radar, camera or ADAS module may require programming, configuration, calibration or alignment before the system will operate correctly.

U0104 vs U0405 #

These two codes concern the same general system but describe different failures.

U0104 means the expected communication from the cruise-control-related module was lost.

U0405 means a module received data from the cruise control module but considered that data invalid or implausible.

In simplified terms:

• U0104: the expected messages are missing;
• U0405: messages are received, but their content is considered invalid.

The diagnostic approach is therefore not identical.

U0104 After a Dead Battery #

A deeply discharged battery can cause control modules to shut down or reset at different moments.

This can temporarily generate communication DTCs.

If U0104 appeared during a confirmed low-voltage event:

• fully charge and test the battery;
• check the charging system;
• record all fault codes;
• clear the codes after repairs;
• perform another full-system scan.

If U0104 does not return and all modules communicate normally, the fault may have been associated with the previous voltage event.

If it returns as a current DTC, continue diagnosis.

U0104 With Multiple U-Codes #

If U0104 appears together with numerous “Lost Communication” codes, do not replace several modules.

Look first for a common cause such as:

• low system voltage;
• gateway failure;
• shared power supply;
• shared ground;
• network wiring damage;
• a module pulling the network down;
• software or configuration issues.

A full network topology is particularly valuable in this situation.

Can Aftermarket Equipment Cause U0104? #

Potentially.

Devices connected to vehicle power or communication circuits can cause problems if installed incorrectly.

Examples can include:

• remote-start systems;
• trackers;
• alarm systems;
• telematics equipment;
• incorrectly installed accessories;
• devices connected directly to CAN wiring.

If the fault began after aftermarket installation, inspect the modified circuits carefully.

Can You Drive With U0104? #

Many vehicles remain driveable with U0104 if the only affected function is cruise control.

However, cruise control or adaptive cruise control may be unavailable.

If the affected module also supports additional driver-assistance features, those functions may also be disabled.

If U0104 is accompanied by braking, steering, stability-control, collision-warning or other safety-system warnings, diagnose the complete fault set before relying on those systems.

Does U0104 Mean the Cruise Control Module Is Bad? #

No.

U0104 means communication was lost. It does not identify why communication stopped.

Check power, grounds, fuses, connectors, network wiring, system voltage and applicable software information before replacing the module.

Can Low Battery Voltage Cause U0104? #

Yes, a low-voltage event can cause a module to reset or temporarily stop transmitting messages.

This is particularly relevant if multiple communication codes appeared at the same time or the vehicle recently had battery or starting problems.

If U0104 repeatedly returns with normal system voltage, continue with the network and module-specific diagnosis.

Should I Replace the Module if It Is Offline? #

Not immediately.

A module with no power, no ground or a disconnected network wire will also appear offline.

Verify the external circuits first.

If replacement is eventually required, check whether programming, parameter configuration, security access, camera calibration or radar alignment is necessary.

Common Repairs for U0104 #

The correct repair depends on the confirmed cause. Possible repairs include:

• repairing a module power supply;
• repairing a ground connection;
• replacing a blown fuse after identifying why it failed;
• repairing damaged CAN wiring;
• repairing corroded or loose connector terminals;
• repairing a gateway or network connection;
• correcting aftermarket wiring;
• charging or replacing a confirmed faulty 12V battery;
• performing an applicable manufacturer software update;
• replacing and programming the affected module only when diagnosis confirms internal failure.

Common U0104 Diagnostic Mistakes #

• Replacing the cruise control module immediately. Loss of communication can be caused by power, ground or network faults.
• Assuming every vehicle has a separate cruise module. The function may be integrated into a camera, radar or ADAS controller.
• Using only an engine-code reader. A full-system scan is much more useful for network faults.
• Clearing codes before recording them. Companion codes can reveal the original failure.
• Assuming 60 ohms at the DLC is a universal CAN test. Network architecture varies between vehicles.
• Ignoring battery voltage. Low voltage can create temporary network faults.
• Replacing a module without checking service bulletins. Some documented U0104 cases are software-related.
• Installing a used or replacement module without considering programming or calibration.

Related OBD2 Codes #

• U0405 — Invalid Data Received From Cruise Control Module
• U0100 — Lost Communication With ECM/PCM
• U0121 — Lost Communication With ABS Control Module
• U0140 — Lost Communication With Body Control Module
• U3003 — Battery Voltage

Browse the Network and Communication OBD2 Codes section for additional CAN bus and control-module communication faults.

U0104 FAQ #

What should I check first for U0104? #

Perform a full vehicle scan, identify which module stored U0104, check whether the cruise-control-related module currently communicates, then verify its power and ground circuits.

Can a fuse cause U0104? #

Yes. If a fuse removes power from the module, that module can disappear from the network and other controllers may store U0104.

Can U0104 be intermittent? #

Yes. Temporary low voltage, loose terminals, wiring movement, software conditions or an intermittent module reset can produce a stored U0104 even if communication later returns.

Is U0104 the same as U0405? #

No. U0104 indicates lost communication. U0405 indicates that communication occurred but the received data was considered invalid.

Do I need a CAN oscilloscope? #

Not for every case. Many U0104 faults can be diagnosed through a full-system scan, power and ground testing, connector inspection and wiring checks. An oscilloscope becomes useful when a network waveform or intermittent bus fault needs deeper analysis.