U0115
Lost Communication With ECM/PCM B
Communication network (powertrain)
Generic OBD-II
High
What it means
U0115 means a module on the network has lost communication with the engine/powertrain control module (ECM/PCM B). Because this module runs the engine, the fault can cause a no-start, stalling, or limp mode, and it usually points to a power, ground, or bus wiring problem at the module rather than the engine itself.
High
Can I keep driving? Often not safely — losing communication with an engine control module can cause a no-start, stalling, or limp mode, so limit driving until it's diagnosed.
Common symptoms
What you'll notice
- Check-engine light on, often with reduced power or limp mode
- No-start, hard start, or stalling
- Multiple powertrain-related codes set at once
- ECM/PCM B not responding to a scan tool
Common causes
Most likely first
- Loss of power or ground to the ECM/PCMLikely
- Blown fuse feeding the control moduleCommon
- Corroded, damaged, or loose connectors and wiring at the moduleCommon
- CAN bus wiring fault isolating the module from the networkLess often
- Failed ECM/PCMLess often
How to diagnose & fix
Work through it in order
- Scan all modules and confirm ECM/PCM B is unreachable, noting any companion codes.
- Check battery voltage and the module's fuses, power feeds, and grounds first.
- Inspect the module's connectors and harness for corrosion, damage, or water intrusion.
- Test the CAN bus wiring between the module and the network for opens or shorts.
- If power, grounds, and bus wiring check out, suspect the module — replace and program it as required, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with U0115?+
No — losing communication with an engine control module can cause a no-start or stall at any time, so have it diagnosed before driving.
Can I just clear U0115?+
You can try, but it returns immediately if the module truly isn't communicating, and the drivability risk remains until the wiring or module is fixed.
Related codes
Often seen with U0115
Read & clear U0115 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX