U0115

Lost Communication With ECM/PCM B

Q: 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.

Q: 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.

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.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear U0115 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX