What it means
A control module has detected that its software/calibration is incompatible with the cruise control module. Cruise control may be disabled until matching software is flashed.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The cruise control module manages cruise functions and shares its software identity and status with other controllers. U0305 sets when a module detects that the cruise module's software or calibration is incompatible with the expected version. A mismatched replacement, incomplete update, incorrect coding, or gateway message-routing issue can cause cruise control to be disabled.
Common causes
Most likely first.
- Software/calibration mismatch with cruise module
- Used cruise module from different vehicle fitted
- Gateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules for U0305 and related cruise-control or communication faults, and save freeze-frame data.
- Check whether cruise control is unavailable and review recent repairs for a cruise module replacement, programming, or coding change.
- Use a capable scan tool to compare the cruise module's software and calibration identifiers with the vehicle's required configuration.
- Inspect the cruise module connector and harness for damage or a poor connection that could interrupt communication.
- Check gateway configuration and have any software or coding mismatch corrected using the manufacturer's procedure, then rescan.
Common fixes
- Secure the cruise module connector or repair damaged wiring affecting its communication.
- Correct cruise module or gateway coding that does not match the vehicle.
- Complete or repeat an interrupted software update with the compatible calibration.
- Program a replacement cruise control module for the vehicle; replace it only if programming fails or incompatibility remains.
Can I keep driving?
The vehicle can generally be driven if normal acceleration and braking are unaffected, but do not rely on cruise control. If the fault appears with other warnings or changes in throttle response, stop using the vehicle until those issues are checked.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.