U0115 — Lost Communication With ECM/PCM "B"

vehicle network

Is it safe to drive?

Drive with caution Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm U0115 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the vehicle network (CAN bus) communication for damage, corrosion, chafing or poor contact.
  4. Subsystem check Measure resistance between CAN-High and CAN-Low at the OBD port with power off — about 60 Ω is healthy.
  5. Subsystem check Scan all modules: the one that does not respond is either the culprit or downstream of the break.
  6. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0115 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for U0115 (parts and labor, USD, independent shop rates): Repair CAN wiring or connectors: $100–$400; Remove interfering aftermarket device: $0–$150; Replace the faulty control module: $300–$1,500. Overall, fixing U0115 usually costs between $0 and $1,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code U0115 mean?

Lost Communication With ECM/PCM "B" (U0115): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by a faulty module pulling the bus down, poor grounds or low battery voltage, water ingress in harness junctions.

How do I diagnose U0115 myself?

Start with a scan: confirm U0115, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the vehicle network (CAN bus) communication, and verify the suspect component against live data before buying parts.

Is it safe to drive with U0115?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

What are the symptoms of U0115?

Drivers most often notice: random, hard-to-reproduce electrical glitches, no-start or intermittent starting in some cases, multiple warning lights on at once, modules intermittently not communicating with the scanner.

How much does it cost to fix U0115?

Repair CAN wiring or connectors — $100–$400; Remove interfering aftermarket device — $0–$150; Replace the faulty control module — $300–$1,500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What does U0115 mean?

The engine control module sets U0115 when it detects a fault in the vehicle network (CAN bus) communication. In practical terms: lost communication with ECM/PCM "B". The code belongs to the vehicle network group of OBD2 codes.

This code does not appear from a single bad reading: the module must see the fault condition repeat under defined operating conditions before it turns on the warning light. The freeze frame captured with U0115 — engine load, rpm, temperature, speed — tells you exactly when the problem occurs, so reproduce those conditions when testing.

Common symptoms of U0115

  • random, hard-to-reproduce electrical glitches
  • no-start or intermittent starting in some cases
  • multiple warning lights on at once
  • modules intermittently not communicating with the scanner
  • intermittent loss of functions (gauges, windows, steering assist)

What causes U0115?

  • aftermarket equipment interfering with the bus
  • a faulty module pulling the bus down
  • corroded connectors, especially in wet areas
  • water ingress in harness junctions
  • poor grounds or low battery voltage
  • damaged CAN bus wiring or short to power/ground

How to diagnose U0115

  1. Connect an OBD2 scanner, confirm U0115 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Visually inspect the wiring harness and connectors related to the vehicle network (CAN bus) communication for damage, corrosion, chafing or poor contact.
  4. Measure resistance between CAN-High and CAN-Low at the OBD port with power off — about 60 Ω is healthy.
  5. Scan all modules: the one that does not respond is either the culprit or downstream of the break.
  6. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0115 does not return.

How to fix U0115

Start with the cheapest and most common causes before replacing expensive parts:

  • Repair CAN wiring or connectors — $100–$400
  • Remove interfering aftermarket device — $0–$150
  • Replace the faulty control module — $300–$1,500

How much does it cost to fix U0115?

Repair cost depends on which component actually failed. Typical scenarios for U0115 (parts and labor, USD, independent shop rates):

  • Repair CAN wiring or connectors: $100–$400
  • Remove interfering aftermarket device: $0–$150
  • Replace the faulty control module: $300–$1,500

Overall, fixing U0115 usually costs between $0 and $1,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U0115?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

Related OBD2 codes