U0299 code meaning
Lost Communication With DC/DC Converter Control Module B
Network system Generic code U02xx codes Check engine light
What U0299 means
A second DC/DC converter, B, appears where a single support stage cannot serve every consumer or where two networks are fed separately. FCA documents the code: in PCM reflash bulletins 18-023-19 Rev. B and 18-020-21, covering 2019 Cherokee models with the 3.2 V6 and stop-start, U0299 is named as loss of contact to DC-DC converter 2. Next to it stand performance and over-temperature codes for converter 2 (P0EA5, P0EA6) and invalid data from converters A and B. Customers report a lit MIL and an engine that does not always restart after an auto stop; the remedy is new PCM software, not a new converter. With B missing, start-stop is typically withdrawn and voltage-sensitive electronics may reset during restarts.
U0299 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of U0299
- Check engine lamp on
- Engine does not always restart after auto stop
- Start-stop function disabled
Common causes of U0299
- Most likelyPowertrain control module software (FCA update)
- PossibleSupply, fuse or ground of converter B faulty
- PossibleBus wiring or connector to converter B damaged
- Less likelyConverter B internally failed, e.g. after overheating
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Dc dc converter module bVehicle bus wiring
What each part of U0299 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 99 | The exact fault in that area. |
What to do next
- Note U0299 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 U0299
What does U0299 mean?
U0299 means "Lost Communication With DC/DC Converter Control Module B". A second DC/DC converter, B, appears where a single support stage cannot serve every consumer or where two networks are fed separately. It is a generic code, so it means the same on every make.
Is it safe to drive with U0299?
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 U0299 fail an emissions test?
Yes, it can. U0299 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 U0299 to fix?
Difficulty: medium. A typical repair takes 0.3 to 4 hours of work. This is a job for a workshop.
Will U0299 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.