U0027 — Low Speed CAN Communication Bus (-) shorted to Bus (+)

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 U0027 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 U0027 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for U0027 (parts and labor, USD, independent shop rates): Remove interfering aftermarket device: $0–$150; Repair CAN wiring or connectors: $100–$400; Replace the faulty control module: $300–$1,500. Overall, fixing U0027 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 U0027 mean?

Low Speed CAN Communication Bus (-) shorted to Bus (+) (U0027): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by water ingress in harness junctions, aftermarket equipment interfering with the bus, corroded connectors, especially in wet areas.

Is it safe to drive with U0027?

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 is the most common cause of U0027?

The most common causes are: water ingress in harness junctions, aftermarket equipment interfering with the bus, corroded connectors, especially in wet areas.

How do I diagnose U0027 myself?

Start with a scan: confirm U0027, 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.

How much does it cost to fix U0027?

Remove interfering aftermarket device — $0–$150; Repair CAN wiring or connectors — $100–$400; 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 U0027 mean?

Behind U0027 is a specific failure in the vehicle network (CAN bus) communication: low speed CAN communication bus (-) shorted to bus (+). The onboard computer stores it in the vehicle network group after verifying the fault over repeated checks.

To set U0027, the control module compares live readings of the vehicle network (CAN bus) communication against calibrated limits, usually over several drive cycles. Alongside the code it stores a freeze frame — a snapshot of rpm, load, coolant temperature and vehicle speed at the moment of failure. Reading that snapshot first saves diagnostic time.

Common symptoms of U0027

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

What causes U0027?

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

How to diagnose U0027

  1. Connect an OBD2 scanner, confirm U0027 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 U0027 does not return.

How to fix U0027

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

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

How much does it cost to fix U0027?

Repair cost depends on which component actually failed. Typical scenarios for U0027 (parts and labor, USD, independent shop rates):

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

Overall, fixing U0027 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 U0027?

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