U0115Lost Communication With ECM/PCM B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- MIL or engine/drive system warning
- No start or no READY on hybrids
- Often no driveability complaint when the code is software-related
- Likely causes
- 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
- RareECM/PCM B internally faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €50 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.