U0115 code meaning
Lost Communication With ECM/PCM B
Network system Generic code U01xx codes Check engine light
What U0115 means
U0115 is set when a second engine or powertrain controller, ECM/PCM B, vanishes from the bus; U0100 belongs to unit A. What B stands for depends on the maker: GM's Saab 9-5 and 9-4X lists call it ECM 2, Mercedes-Benz assigns U011500 to its drivetrain control unit. In the 2021 S 580, the 48 V integrated starter alternator logged U0115 with U0168 because of its own software; the MIL went out after three drive cycles, release 20.B cured it (LI15.40-P-073663). The DC/DC converter of the EQB and electric G-Class records it after wake-up faults (LI54.10-P-079533). Mazda (09-027-26) sees it on the CX-90/CX-70 PHEV, together with P0AB9, as a cold-weather no-READY caused by moisture at luggage-area connector 3002-411.
U0115 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0115
- MIL or engine/drive system warning
- No start or no READY on hybrids
- Often no driveability complaint when the code is software-related
Common causes of U0115
- Most likelySoftware fault in the reporting or the B controller (updates released)
- PossibleWater ingress or corroded terminals on the bus or relay connectors
- PossibleController B not powered or not woken up in time
- Less likelyECM/PCM B internally faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ECMCAN bus wiring
What each part of U0115 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 15 | The exact fault in that area. |
What to do next
- Note U0115 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 U0115
What does U0115 mean?
U0115 means "Lost Communication With ECM/PCM B". U0115 is set when a second engine or powertrain controller, ECM/PCM B, vanishes from the bus; U0100 belongs to unit A. It is a generic code, so it means the same on every make.
Is it safe to drive with U0115?
Drive gently and only to a workshop. With U0115 the car can go into limp mode (reduced power) to protect itself.
Will U0115 fail an emissions test?
Yes, it can. U0115 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 U0115 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will U0115 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.