OBD-II trouble code
U0104: Lost Communication with Cruise Control Module
A module on the network can no longer hear from the cruise control module. Usually a power, ground, or wiring fault — and on vehicles with adaptive cruise control, the radar-based following and speed features go offline along with conventional cruise.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,200
- DIY difficulty
- Shop recommended
What does U0104 mean?
U0104 is set when another module on the vehicle's communication network stops receiving messages from the cruise control module. On older systems this module manages conventional cruise control. On modern vehicles it is usually the adaptive cruise control (ACC) module — typically the forward-facing radar unit behind the grille or bumper — which maintains a set speed and automatically adjusts following distance to the vehicle ahead. It reports its status over the network so the powertrain and braking modules can respond to its requests.
The causes follow the familiar communication-code pattern. The module may have lost power or ground through a blown fuse, corroded ground, or failed relay. The CAN wiring or connector at the module can be damaged or corroded — and because the radar unit lives at the front of the vehicle behind the grille, it is exposed to moisture, road debris, and the effects of minor front-end impacts that disturb its connector or alignment. The module's internal communication circuitry can fail, or another module on the bus can disrupt communication for everyone. Low system voltage from a weak battery or charging fault can also cause intermittent dropouts.
The symptoms are usually limited to driver-assistance features. Cruise control won't set or will cancel, and on ACC-equipped vehicles the adaptive following, collision-warning, and sometimes automatic-braking features become unavailable with a message on the dash. The check engine light may come on, often with companion driver-assistance codes. The vehicle drives normally otherwise, but losing automatic braking and following on an ACC system is a meaningful safety reduction, so it's worth diagnosing promptly rather than ignoring.
Common causes
- Blown power or ground fuse for the cruise control / ACC module
- Corroded or loose ground at the module
- Damaged CAN wiring to the cruise control module
- Corroded or backed-out terminals at the radar/module connector
- Front-end impact or debris disturbing the radar unit or its connector
- Failed internal communication circuitry in the module
- Another module on the bus disrupting network communication
- Low system voltage from a weak battery or charging fault
Symptoms
- Cruise control won't set or cancels immediately
- Adaptive cruise, following distance, or collision warning unavailable
- Driver-assistance warning message on the dash
- Check engine light on, often with driver-assistance codes
- Scan tool can't communicate with the cruise control module specifically
- Symptoms may be intermittent with a marginal connection
- Other U-codes stored in modules that depend on the cruise module's data
Diagnostic steps
- 1.Scan all modules; confirm the cruise control module is the one that's unreachable while others respond.
- 2.Check the module's power and ground fuses and the relevant relays.
- 3.Inspect the module/radar connector and ground for corrosion, looseness, and any sign of front-end impact or debris.
- 4.Measure CAN-High and CAN-Low at the module connector (rest near 2.5 volts) and verify continuity back to the bus.
- 5.Test the battery and charging system, since low voltage can cause intermittent communication loss.
- 6.If power, ground, and wiring are good but the module still won't communicate, the module itself is the likely failure and will need replacement, programming, and on ACC systems a radar alignment.
Repair cost
$100 – $1,200
A blown fuse, corroded ground, or connector repair is the cheapest fix at $100-$300 once located. Wiring repair runs $200-$600. Diagnostic time commonly adds $150-$300. Replacing an adaptive cruise radar/control module is the most expensive outcome at $400-$1,200 including programming and radar alignment, and is a last resort after cheaper causes are ruled out. Conventional (non-radar) cruise modules sit at the lower end.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.