U029F code meaning
Lost Communication With Evaporative Emission System Leak Detection Control Module
Network system Generic code U02xx codes Check engine light
What U029F means
Some evaporative systems run the leak test through a separate module that holds its own valve, pressure switch or sensor and reports results to the engine controller. U029F is stored when those reports no longer arrive. Kia documents it for the Niro hybrid of 2017 to 2019: bulletin PS593 describes a MIL with U029F00 and, on cars built before October 2018, asks for a resistance check of the yellow signal wire between pin 12 of joint connector EF11 and pin 2 of the natural vacuum leak detection plug F56, since damaged insulation or corroded strands near F56 cause an open circuit. Ford's 2014 code list marks the code as a MIL code. CARB 1968.2 requires gasoline vehicles to find leaks as small as 0.020 inch, so the EVAP monitor cannot run. Driving is not affected.
U029F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of U029F
- MIL on
- EVAP readiness not set
- No noticeable change in driving
Common causes of U029F
- Most likelyDamaged insulation or corroded strands in the module signal wire
- PossibleCorrosion or water at the leak detection module connector
- PossibleSupply or ground of the leak detection module interrupted
- Less likelyLeak detection module internally failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EVAP leak detection moduleVehicle bus wiring
What each part of U029F means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9F | The exact fault in that area. |
What to do next
- Note U029F and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U029F
What does U029F mean?
U029F means "Lost Communication With Evaporative Emission System Leak Detection Control Module". Some evaporative systems run the leak test through a separate module that holds its own valve, pressure switch or sensor and reports results to the engine controller. It is a generic code, so it means the same on every make.
Is it safe to drive with U029F?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U029F fail an emissions test?
Yes, it can. U029F is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U029F to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U029F clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.